The NASA Radio Jove Project

Arnold, Steven

doi:10.1007/978-1-4614-8157-7_7

Steven Arnold²

Part of the book series: The Patrick Moore Practical Astronomy Series ((PATRICKMOORE))

1968 Accesses

Abstract

A quick search on the internet will reveal a great deal of information about how to use a short wave radio receiver, to receive radio emissions from the planet Jupiter and from the Sun. Some of the information and ideas that have been posted are good, but some are quite frankly wrong. Starting with the correct equipment gives the best chance of success. To use optical astronomy again for a moment for an example, if entering the hobby by purchasing one of the “department store” telescopes with their poor optics, very shaky mounts with poor telescope controls and the ridiculous magnification claims of ×600 for a 60 millimeters (2.4 inch) aperture. They will get fed up trying to operate the telescope and will soon lose interest and move on. Whereas, the advice from a fellow astronomer would probably be to purchase a good pair of binoculars and a good star map as a first step.

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7.1 About Radio Jove

A quick search on the internet will reveal a great deal of information about how to use a short wave radio receiver, to receive radio emissions from the planet Jupiter and from the Sun. Some of the information and ideas that have been posted are good, but some are quite frankly wrong. Starting with the correct equipment gives the best chance of success. To use optical astronomy again for a moment for an example, if entering the hobby by purchasing one of the “department store” telescopes with their poor optics, very shaky mounts with poor telescope controls and the ridiculous magnification claims of ×600 for a 60 millimeters (2.4 inch) aperture. They will get fed up trying to operate the telescope and will soon lose interest and move on. Whereas, the advice from a fellow astronomer would probably be to purchase a good pair of binoculars and a good star map as a first step.

Radio astronomy is no different. There are claims on the internet saying that it is possible to receive radio emissions from Jupiter with a small loop antenna of about 600 millimeters (24 inches) in diameter. This may be in the realm of possibility, but don’t bet any money on it working. Also not any old short wave receiver will do, a receiver must be found where our old nemesis the automatic gain control (AGC) can be switched off, disabled, or bypassed. In many cases this cannot be done, and attempts to do so may stop the radio from working. Even if this is managed the problem of knowing whether or not the receiver was receiving the right type of signal would still be there.

Step forward the Radio Jove receiver. The Radio Jove receiver works on a narrow frequency range centered around 20.1 megahertz, and was designed specially to receive the radio emissions from the planet Jupiter and from the Sun, and it does exactly that.

The Radio Jove project is an education and public outreach program involving scientists and teachers from NASA and other organizations. This program supplies a relatively cheap kit capable of receiving radio emissions from the planet Jupiter and the Sun. The kit includes parts numbering a little over 100, and the user assembles the receiver for themselves, although a pre-built and pre-tested receiver can be purchased for an extra charge. As supplied, the kit has everything needed to start on the road to running a successful solar and Jovian radio telescope. The only other items required are a 12 volt power supply (this can be a battery), a pair of headphones or external powered speaker(s), and the poles from which to hang the antenna. These poles can be metal, wood or plastic, but plastic has the habit of flexing quite a bit, especially when working at height. Figure 7.1 shows the kit as it arrives from the Radio Jove team after unpacking

The kit contains five small plastic bags which are numbered, and each one contains different components, for example resistors, capacitors, etc., along with the circuit board, power cable connections, an aluminum enclosure, antenna connections, six ceramic insulators, a coil of copper wire (from which the antenna is to be made), and a coil of RG59/U antenna cable. Two CD-ROMs are also included, accompanied by a very clear and easy to understand instruction manual. The CD-ROMs contain lots of useful information and visual aids, plus tutorials on the art of soldering and useful programs such as Radio Jupiter Pro and Radio-SkyPipe. These programs will be discussed later in the chapter. Something missing from this image is the RF 2080 calibrator, as this wasn’t available at the time the kit was purchased, and was ordered later. The calibrator and its uses will also be discussed later in the chapter, if thinking of purchasing a Radio Jove kit it would be a good idea to order one of these calibrators at the same time, as they are a very useful accessory, and if one is ordered at the same time as the Radio Jove kit there should be only one lot of postage to pay.

Before ordering a Radio Jove kit it is vital to note that the antenna is of a dual di-pole design and will require a reasonably large area to erect it. The two di-poles each measure 7.6 meters (25 feet) in length and are placed at a distance of 6 meters (20 feet) apart.

Depending where in the world the kit is to be used, and the height at which the Sun and Jupiter transits above the local horizon, the height at which the antenna is used can range from 3 meters (10 feet) up to 6 meters (20 feet). If short on space a single di-pole antenna can be used and still be able to receive Jupiter, but a single di-pole antenna will not have the same gain. A single di-pole antenna can however easily pick up radio emissions from the Sun. The Radio Jove website is a good place to start for specific questions on the subject as there is plenty of useful information there to be explored in addition to a list of mentors who may be emailed directly with questions. An electronic newsletter is also produced two or three times a year and can be downloaded from the Radio Jove web site. The newsletters are full of useful information about what is happening in the world of Radio Jove, and contain images sent in from Radio Jove users all around the world. There is also an excellent online server sign up to receive email messages from other Radio Jove users around the world. This server can be of great interest, and shows how other Radio Jove users in different countries have received the same radio emission, plus any updates to software that are available. Occasionally the Radio Jove team run a phone-in where Radio Jove users can call in and discuss all aspects of the Radio Jove project with the Radio Jove mentors.

7.2 A Guide to Building the Radio Jove Receiver

Building of the Radio Jove receiver is estimated to take approximately 9 hours, but this is only an estimate and it may take longer or shorter depending on the builders capabilities. Looking at the manual there is a list of resistors, capacitors, inductors, integrated circuits, transistors, and the other items such as power connections, etc. Images of all the components are included. Within the manual are two columns, one is for parts identification and the other is for part installation, and each one should be ticked after identification and installation has taken place. This may sound like stating the obvious, but if this is done religiously, then if having to stop for whatever reason, for example the telephone rings, it can be easy to pick up and continue from where left off.

Before starting to identify the components it’s a good idea to use small stickers, something along the lines of the size used for price tickets in shops. These can be obtained from any office supply store. Work on only one type of component at a time. The manual lists capacitors first, and although they number up to 44 there are in fact 43. This is because capacitor number 7 is no longer used but is still listed. After the first capacitor has been positively identified fold a small sticker around one of the wire connections and mark it C1, and tick the column within the manual. Carry on until all of the capacitors have been identified and labeled. Then do the same with the resistors, of which there are 32. Start with R1 and carry on until all of the others have been identified and tagged. Please note that resistor number 32 does not fit on to the circuit board, and be sure to keep this component separate and in a safe place for the moment. Do the same labeling of the other components, until each and every one has been positively identified and had the corresponding box in the manual ticked. It will be noticed that there is a large silver colored, rectangular shaped object within the components. This is a 20 megahertz crystal, and this should be soldered in place with the other components on the circuit board. The purpose of this crystal is to tune the receiver, and it can only be fitted in one position so there will be no problems with it orientation.

This may come across as rather time consuming, but when soldering each part into location it’s just a matter of looking for the right number on the components sticker, and this also acts as a double check if forgetting to tick the column within the manual.

There were two components which identification was a problem. These were zener diodes ZD1 and ZD2 as their marking on the case were slightly different than the marks shown within the manual. ZD1 was marked within the manual as 1 N753 but the diode case read F53A, and ZD2 was marked in the manual as 1 N5231 but the diode case read F231B. This is not uncommon when building projects from kits, as different manufacturers have different markings or even different colors for the same component, but a quick search on the internet soon sorted out which one was which.

Notice also within the construction manual the term “jumper wires” will be used, these are just short lengths of connecting wire that are soldered on to the circuit board to link different parts of the circuit together to complete the electrical circuit in a convenient place.

Looking at the aluminum enclosure, don’t assemble this yet, but notice the edges are quite sharp from where they have been cut on a sheet metal cutter. Within the kit there should be a small piece of sandpaper, and it’s a good idea to give each edge a light sanding to remove these sharp edges, this will save fingers from being cut on assembly of the enclosure. After sanding it is best to wipe each piece with a clean damp cloth to remove any aluminum dust or shavings, as these can cause short circuits if any get in contact with electrical components. These can then be dried and put away for use later, but leave out the front and rear panels. The front panel has two large holes and one small hole, and the rear has four large holes and one smaller hole. Included within the kit are front and rear decals, these can be peeled off the card and fitted to each panel, taking care to avoid trapping any air, as this can leave unsightly bubbles. After fitting the decals these panels can now be put away with the other parts of the enclosure for use later.

It is time to start soldering in the components, but first get the circuit board in the right orientation. Handle the circuit board on its edges like a DVD, as oils within the fingers can stop solder from forming a good joint. Look for the Radio Jove 20.1 megahertz receiver printed on the circuit board, as this indicates the top of the circuit board and the front edge (see images below). Look at the holes where the components will be fitted, the circuit board is marked with the number of the component that fits in each hole, and the polarity of polarity-sensitive components are also indicated.

Components like resistors and ceramic capacitors will need their connecting wires bending so they can be fitted into the circuit board. Don’t be tempted just to bend them, as if they are bent too close to their ceramic body this can damage the ceramic and this could cause the part to fail, either immediately or at a later stage. It is better to use a pair of needle nose pliers to hold the connecting wire near the ceramic body to support it, and then bend the connecting wire with the fingers. It’s also a good idea when bending the connecting wires of an electrolytic capacitor so it can be fitted on to the circuit board not to let the connecting wires from the capacitor come in contact with the case itself. Although they should be insulated it is not worth the risk.

Start by soldering in the resistors first, as they can best put up with the heat of soldering. After each component has been soldered into place turn the board over and trim the excess wire off with a sharp pair of cutters. It is a good idea to have a little container handy to drop these into, as there will be around 200 of these left after building the receiver and they have the habit of getting everyway like needles from a Christmas tree (and are just as unpleasant if not worse to stand on). The last thing to be fitted to the circuit board is the integrated circuits. These can sometimes require a slight bending of the ICs contacts so they can be fitted into their IC socket, but be very careful fitting these as they are easily damaged. After finishing soldering in all the components, it should look like the image (Fig. 7.2).

It is now time to fit the antenna input socket, power input socket and audio output sockets to the rear panel. This is just a case of putting them through the pre-drilled holes and applying a locking washer and a nut. These only need slight pressure applying to the nut, with a pair of pliers to hold them secure. The circuit board is now fitted to the base of the enclosure. It is mounted on spacers to stop the bottom of the circuit board coming in contact with the aluminum base and causing a short circuit. The rest of the enclosure needs to be built now. This is just a simple case of fitting four channels to one of the ends, and fixing them in with screws, and then sliding in the bottom, front and back panels and securing them with four screws on the other end. The top is left off at this stage as the connection to the antenna, power supply and audio inputs and outputs need to be made. The two control knobs for power/volume and tuning can now be fitted. The resistor number R32 (51 ohm) is now temporally soldered onto the antenna input connection. The purpose of this resistor is to simulate an antenna being used with the receiver, by producing a “dummy load” on the receiver circuit, and this will be removed after testing and tuning of the receiver itself. Once this has been done it should look like the image (Fig. 7.3).

The receiver is now ready for testing and tuning, and this can be done in several different ways depending on the level of equipment available for use. First, a suitable power supply will be needed to power the receiver.

7.2.1 Power Supplies for the Radio Jove Receiver

If unhappy or unsure about using mains/grid voltage, ask the advice of a qualified electrician first. A 12 volt power supply is needed for the Radio Jove receiver, and this can be a battery, such as a car battery. Either use the battery on its own or working through the vehicle’s cigarette lighter socket, NOT with the engine running.

If mains/grid power is to be used beware that a well-regulated transformer is needed, not the cheap ones used for running games consoles. Batteries produce power through a chemical reaction and therefore produce true direct current (DC).

A transformer works off an alternating current (AC) and steps it down from mains/grid voltage to a smaller voltage, in our case 12 volts to run the Radio Jove receiver. Many of the cheaper transformers’ outputs have very poor rectification properties. If a display of the output of a battery or a well-regulated transformer were to be displayed on an oscilloscope a straight line would be seen, on the other hand if the display of the output from one of the cheaper transformers were seen on the oscilloscope rippling, or in some cases very big spikes, would be seen on the display.

This type is alright for running games, etc., but NOT for the Radio Jove receiver or other radio receivers discussed here.

As these spikes and ripples within the power supply introduce noise within the receiver’s electronics. This is a bad thing, as the signal we want to receive is a form of noise, it makes sense not to artificially introduce noise into the receiver. Steer well clear of those transformers that have a voltage selection switch on them to enable different voltages to be selected for different items. It has been found through experience that the voltage marked on the transformer has nothing whatsoever to do with the voltage coming out! After blowing an LED light cluster by setting the transformer to the so-called correct voltage and polarity marked on the side, a quick check is always made of the output of these variable transformers with a voltage check on a multimeter first. This ensures that the voltage and polarity are correct. This simple precaution can save money in the long run.

7.2.2 Testing and Tuning the Receiver

Before switching on the power make sure the polarity of the power supply is correct. The inner part of the power connection is positive and the outer part is negative. This can be done by doing a quick check with a multimeter set on the voltage setting. Apply the test probes to the output of the power supply, with the positive probe at the center and the negative on the outer part, the voltage reading should be 12 volt. If the reading is −12 volt then the polarity is wrong and must be changed before it is applied to the receiver, or the receiver will not work or be permanently damaged. Once the power supply has been correctly identified, it can now be plugged into the power input socket of the receiver.

The receiver must be “tuned” before it can be used. There are several ways of doing this depending on the level of test equipment that is available. If no test equipment is available to tune the circuit, it can be done by listening to the tone of the receiver and adjusting the tuning until a constant pitch is heard, or by using the program Radio-SkyPipe to chart the changes in the output of the receiver. It will be possible to see any drifting in the output of the receiver on the graph produced by the Radio-SkyPipe program on the computers screen, and changes to the receiver can be made accordingly. Another method is to use a multimeter that is capable of measuring audio frequency voltages to measure the output from the receiver itself. The last method of tuning is to use an oscilloscope to monitor the output. This gives a visual reference to watch to see how the output changes. Please see Fig. 7.4.

It is also a good idea to have either headphones or externally powered speaker(s) to hand. After choosing the preferred method of tuning, and after all necessary test equipment and headphones or speaker(s) have been fitted, it is time to switch on the receiver for the first time. Don’t put the headphones on just yet. There should be a high-pitched noise coming from the headphones or external speaker(s). This is the noise being generated within the circuit from the 20 megahertz crystal mentioned earlier.

It would be a good idea to run the finished receiver for about 5 minutes before starting the tuning process, as this will allow the receiver circuitry time to “warm up” and stabilize, this will lead to a more accurate tuning.

It is now a matter of adjusting four components to tune the receiver. First, set the tuning knob on the receiver to the 10 o’clock position, and using the plastic tools included within the kit adjust the component L5 (variable inductor) until a loud tone can be heard. Once this is done forget L5 and move on to components C2 (variable capacitor), C6 (variable capacitor) and L4 (variable inductor). These need to be adjusted until the maximum signal strength is produced. When adjusting the components only make very small adjustments at a time, being careful not to force the adjustment screw in either direction as this can damage the internal parts of the component itself. This may sound a little fiddly, but in fact it is quite simple, especially if using the oscilloscope method, as the actual change in strength of the signal can be seen visually. Not everyone will have access to an oscilloscope but there is no reason why the other tuning methods shouldn’t work just as well.

Once the tuning procedure has been completed, and with the power to the receiver switched off, the resistor R32 (51 ohm) can be unsoldered. This resistor must be kept safe in case this tuning procedure needs to be carried out again. A good idea is to stick this resistor to the inside of one of the panels of the enclosure with electrical tape in order to know exactly where to find it if it is needed again. There is one last thing to do before fitting the top to the enclosure, that is to cut through the number 6 “jumper connection” wire. Don’t remove it, just snip through the wire and bend it up so it cannot come in contact with any other part. This removes the tuning crystal from the circuit now that it has completed its job of tuning the receiver. By not removing the “jumper” wire, if the tuning process needs to be repeated for whatever reason the “jumper” wire can soon be reconnected. With all of the above tasks completed, the receiver is ready for use, as shown in the Figs. 7.5 and 7.6. Please note the connections on the rear view of the receiver, in particular the two audio outputs, this is so one output can be used with headphones and the other can be used to connect the receiver to a computer or other device.

7.3 Building the Radio Jove Antennas

The antenna for the Radio Jove receiver is a dual di-pole design. This dual di-pole design gives greater gain then a single di-pole, and with the use of a phasing cable and the height at which the antenna is positioned the center of the beam can be controlled to give the best gain possible for the height of the object, be it the Sun or the planet Jupiter, as it appears above the local horizon.

The kit includes six ceramic insulators, a coil of copper wire, toroid collars, a coil of RG59/U antenna cable with “twist on” F connector fittings and a power combiner. The power combiner is a connection with two inputs and one output. This allows the two di-pole antennas to be coupled into the two inputs and the single output then goes to the Radio Jove receiver. A di-pole antenna is an antenna cut to half the wavelength of the in-coming radio wave that is to be received. In the case of the Radio Jove receiver working at 20.1 megahertz this half wavelength distance is 7.09 meters (23.28 feet). Also within the kit are six ceramic insulators, and the job of the insulators is to allow the antenna wire to hang in free space from the supports, without allowing the antenna wire to come in contact with either of the supports or the antenna cable. This is done by fitting an insulator at the end of each of the antenna wires, plus one in the center of the wire where the antenna cable is connected to the antenna wire itself.

The first task is to unroll the coil of copper wire which is included within the kit and cut it into the correct lengths to make the two di-pole antennas. It can be quite awkward trying to measure the correct lengths of wire while it is in one long coil as it will have the tendency to keep rolling back on itself like a roll of wallpaper. A good way to cut the antenna wire to save on measuring out long lengths of wire is to cut it in half and then half again to have four equal lengths of wire. These will still be too long to make the antenna, but the length allows enough wire to pass through the ceramic insulators and twist it back on itself in order to secure the wire to the insulators.

When the four equal lengths of wire have been cut, start to fix them to the insulators at the correct length. A good way to get this length is to measure out the correct length on a floor and mark this length with two chalk marks, this will save trying to hold the antenna wire and stop it coiling back on itself and at the same time trying to hold a tape measure. It would help to have assistance with this part. Holding one insulator on a chalk mark and an assistant holding one insulator on the other chalk mark, then getting hold of one of the lengths of antenna wire, each person can allow the same amount of wire spare at each end to allow this to be passed through the insulator. After passing the wire through the insulator, twist it back on itself. Don’t go right up to the insulator, as if it is fitted too tightly onto the ceramic insulator it may cause it to crack or the wire may become damaged rubbing against the hard insulator when the antenna moves in the wind. Once this task has been performed there should be two antenna wires of the correct length with an insulator at either end and one in the middle. Don’t solder these in place just yet.

The two antennas can be carefully coiled up and put somewhere safe for the time being. When coiling the antenna wires, try not to let the ceramic insulators knock together as they can soon have their protective glazing damaged. Before discussing the cutting to length of the antenna cable, here are a few points to follow when handling the antenna cable. The antenna cable has a natural twist already formed within the cable itself. When coiling these types of cable allow it to follow this natural twist, and don’t make the loops too small. This will allow the cable to be coiled and uncoiled more easily as opposed to fighting against its natural twist, and the central conducting wire, which is solid in this cable, will not become stressed and so will be less likely to break. It looks neater, and the antenna cable doesn’t take on the look of an old bird’s nest. Under no circumstances allow the antenna wires or the antenna cables to become kinked. If needing to take the antenna cable round a corner, do so with a gentle curving of the wire rather than a sharp bend. This may sound like belaboring the point, but if this practice and these few simple precautions are followed, there is no reason why the antennas shouldn’t provide many years of service.

A good sharp pair of wire cutters will be needed to cut through the antenna cable. Nothing comes across as more amateurish then a length of cable which looks like it has been hacked through with a blunt pair of scissors. This can cause all sorts of problems when trying to fit the connections later on. The antenna cable needs to be cut at set lengths so both of the di-pole antennas will work correctly. The lengths of each cable are cut in factors of the wavelength of the signal that the Radio Jove receiver is going to receive. There are four cables to cut, so it is a good idea to wrap a different color of electrical tape around each of the cut lengths and make a quick note of which color corresponds to which length. This will save time later, as the cable will only need measuring once just before cutting, as it is hard to judge the lengths of cables when they are coiled up.

First, cut the two cables which come from the di-pole antennas. These are of equal length equivalent to one wavelength using the properties of this particular antenna cable supplied. If other cables are used these lengths may be subject to change. Don’t mix different types of antenna cables, as this will cause an impedance miss-match. This first measurement is 9.58 meter (32.31 feet). All the cables must be cut to their exact measurement. Now cut the phasing cable. This is cut to 0.375 of the length of the wavelength, and this equates to 3.69 meters (12.12 feet). The last cable to be cut is the cable that comes from the power combiner to the receiver and is 0.5 of a wavelength, which is equal to 4.93 meters (16.16 feet). After cutting all four cables it may be found there is an inch or so of cable left over. Do not throw this away as it can be used to connect the calibrator to the receiver. A length of 50 millimeters (2 inches) is all that is needed for this.

Next get one of the lengths of cable that will be fitted to the di-pole antenna wire. Slide three of the toroid cores supplied within the kit on to the end of the antenna cable which will be fitted to the antenna wire. These improve the antenna performance and help stop interference entering the open end of the cable. These can be a tight fit, but they should be easy enough to push on. Try not to knock these together or force them on as they can be easily damaged. Slide them down around 500 millimeters (2 feet) and apply a little electrical tape to temporally hold them in place while soldering the connections. Now, strip the outer sleeve of insulation off the end of the antenna cable, to a length of 100 millimeters (4 inches). Take care not to cut into the braided layer underneath. Two or three pieces of braiding will probably be lost, this is normal as long as it doesn’t run into half a dozen or more.

Now carefully untangle this braiding off the inner sleeves insulation. This can be done using the tip of a small screwdriver. Again the tip of a ball point pen can be used for this as this is a nice round end with no sharp edges to it. Once this has been done, twist together all the strands to make one wire. This will be one of the connections. Next, cut off 50 millimeters (2 inches) of the inner insulation sleeve to expose the solid central connection. Be careful not to score the central wire with the knife as this will cause the wire to have a weak spot which could be damaged when the antenna is blown about by the wind. It is now time to start making the connections to the antenna wire. First place the antenna cable over the central insulator and the antenna wire, and hold it in place with a couple of cable ties. Please see Fig. 7.7.

Once the antenna cable has been secured, the connections need to be made from the antenna cable to the antenna wire itself. Start with the braided wire. Twist this around one of the antenna wires on one side of the central insulator, but don’t pull the wire too tight, a little slack should be left to allow the antenna to move in the wind. Next, fit the solid central wire to the antenna wire on the other side of the central insulator. Special care must be taken here, with a gentle curve of the antenna cables central connection bring it up to the antenna wire, and allow enough slack in the antenna wire to allow it to move without undue pressure being applied to the solid central antenna wire, for the same reason as above.

Solder the wires in place. A more powerful soldering iron will be needed, one that is somewhere in the region of 75 watts will do the trick, because of the thickness of the wire used for the antenna. Don’t try and use the 25–30 watts soldering iron used to build the Radio Jove receiver circuit board, as this will not produce adequate heat input into the antenna wire, and any melted solder will just sit on the antenna wire and produce what is known as a “dry” joint. Enough heat must be applied to allow the solder to flow freely through the antenna wires, including the wires from the antenna cable. Once the antenna cable has been soldered onto the antenna wire, solder the twisted antenna wire on each of the insulators at each end of the antenna wire to stop them from coming free. After the soldering has been completed, slide the toroid collars back up to the top of the cable and hold them in place with a cable tie, as shown in the above image.

The open end of the antenna cable must now be waterproofed to keep out moisture and dirt. One way of doing this is to apply electrical tape to the open end of the antenna cable and then apply a waterproof coating to this. This can be done using waterproofing specially made for coaxial cable, but instead an automotive ignition sealer can be used; not the type used to dispel moisture, but the type that leaves behind a thin waterproof skin. Spray a liberal amount all around the open end of the antenna cable, it doesn’t matter if the spray covers other parts such as the insulator. Allow this first coat 10–15 minutes to dry, then apply a second coat of the spray. This should be adequate to waterproof the cable. Depending on annual rainfall if this task is repeated two or three times a year when the joint is dry, this should be enough to top-up the waterproofing action of the spray. If this is done a can of ignition sealer will last for years. A word of caution: don’t use the spray indoors as it has a terrible chemical odor to it, which will fill every room in the home.

The other di-pole antenna can then be constructed in the same way. Once both di-poles have been finished the “F” connectors will need to be fitted to the ends of all the antenna cables. Start by removing 25 millimeters (1 inch) of the outer sleeve of insulation from the antenna cable, remembering to be careful not to damage the braiding underneath. This time only untangle half the length of the braiding and fold this back on itself over the un-braided part. Remove the insulation from the solid central conductor, being careful not to score the central conductor itself. It is now time to fit the “F” connector. Put on the connector with a clockwise twisting motion, apply firm pressure until the threads on the inside of the connector “bite” and the connector will screw itself home. Hand pressure should be enough to fit the connector, and there should be no need to force it on with pliers, although it can get a little tight towards the end and a small amount of pressure can be applied. Once all the “F” connections have been fitted to the antenna cables, wrap a little electrical tape around the end that fits on to the cable itself. Two or three turns should be enough, starting with the tape half on the “F” connector and half on the outer sleeve of the insulation of the antenna cable. This is just a precaution to stop dirt and damp entering through the gap between the connector and the outer sleeve of insulation and corroding the antenna cable. Different colored tape could be used to indicate which cable is which, as this is useful to know until becoming more familiar where each cable fits.

This completes the construction of the antennas, meaning now it is time to fabricate some antenna supports. The antennas are used horizontally polarized, and need to be mounted at a height which will be suitable to get the object, either the Sun or Jupiter, as close to the center of the antenna pattern as possible. The height at which the antennas are mounted can be anything between 3 meters (10 feet) minimum to 6 meters (20 feet) maximum depending on where the antennas are used in the world and the altitude at which the Sun and Jupiter appear in the sky above the local horizon.

Four supports will be needed from which to suspend the antennas, and guide ropes to help steady the supports will also be needed. The supports can either be made of plastic tubing, wood or metal. Plastic is cheap, corrosion resistant, light weight, and can be carried in sections to an observing site and assembled there, but at long lengths plastic tubing can become very flexible and prone to splitting or breaking.

Choosing to use plastic tubing will probably be limiting the antenna height to the lower levels.

Wood is a great all-rounder. It’s relatively cheap to purchase, but in long lengths can prove a little awkward to handle. If a permanent site is in mind then wooden masts permanently fixed into the ground and supported with guide ropes would be great. The only maintenance needed would be the application of a timber preservative once or twice a year. If the antenna supports are permanently sited, it would be a good idea to engineer some sort of pulley system that could remotely alter the height of the antennas from the ground. Metal supports are more expensive than wood or plastic, and they are heavier, and prone to corrosion, but reasonably rigid at longer lengths, especially if supported with good guide ropes.

One idea is to use metal washing line props as these are very useful as antenna supports. These are available from most DIY/hardware stores and are quite cheap to purchase. They are telescopic and can be collapsed down like a whip antenna on a car for easy storage and transport. When folded down they are no longer than about 1 meter (39 inches) in length. They are alright for making observations where the antenna is used up to 4.5 meters (15 feet). Above this they are unsuitable and more rigid supports are needed. Eight of them will be required, cut off the plastic hook at the end of four of them, leave the hook on the other four this is ideal for hanging the antenna. Next, taking the four poles with the plastic hooks still attached, remove the plastic bung from the bottom of each pole, so the thinner of the two poles from the one which has had the hook cut off can be slid inside. Two poles can be easily fitted together to form four longer supports. The poles can be easily drilled to accept fixings for guide ropes. A good idea is to make hoops to fit into the holes in the poles rather than passing the guide rope through the holes in the poles, as any rough edges on the inside of the drilled hole will act as a saw and cut through the guide rope by the motion of the poles moving in the wind. These hoops can be made simply by bending some small diameter metal into a triangular shape and fitting the two open ends inside the poles. These could be made using old round tent pegs or wire coat hangers.

These poles, if erected properly and equipped with guide ropes and checked from time to time, can cope with quite bad weather conditions. Sometimes these poles come with some kind of plastic protective coating, so no painting is required. The quality of this protective coating isn’t great, but they should last quite a few years before the corrosion sets in.

A point worth mentioning about guide ropes. Washing lines are fine for this as they are cheap and come in long lengths, but some come with a metal core surrounded by a plastic sleeve or coating. These must be avoided, as the metal within the rope will disrupt the shape of the antenna pattern, as will any metal nearby, such has a chain link fence (the above metal antenna poles will not affect the antenna pattern). Avoid ropes made with natural fibers, these can soon rot if they are constantly getting wet, and they can also break down by exposure to ultraviolet radiation from the Sun unless they have some sort of ultraviolet protective coating. The best rope for this purpose is nylon rope, which is light weight, very strong, and because it is a washing line and therefore designed to be used outside it will have some kind of ultraviolet coating applied to it to protect it from breaking down in sunlight.

When cutting nylon rope, a good idea is to melt the fibers of the cut ends with a gas cooker ring or candle to prevent the rope from fraying. Guide ropes can be anchored to the ground using metal, wooden or plastic tent pegs. Avoid the small round ones as mentioned earlier, these small round pegs will be forever coming lose and needing to be hammered in again. Use the better quality triangular shaped ones; these are more expensive but worth it in the long run.

7.4 Antenna Configurations

To understand how the antenna works we will use the example of the antenna pattern produced by a single di-pole antenna first. Looking at the Fig. 7.8, the antenna is the line in the center of the ellipse; the ellipse shape is the antenna pattern. This shape would be of a three dimensional pattern as if the antenna was passed through the center of a huge jelly doughnut.

Figure 7.8 shows the maximum gain is in the center of the antenna where the central insulator is situated, the minimum gain is at the ends of the wire itself. The ends of minimum gain can be used to an advantage, if for example there is a constant source of interference, move the antenna so the minimum gain is pointing in the direction of the source of interference. This should help with the interference problem. The antenna for the Radio Jove receiver has many different configurations, but all have the antenna horizontally polarized. The configurations are designed to get the maximum gain out of the antenna when Jupiter or the Sun are at different altitudes in the sky as seen from the local horizon.

The configurations described here will be suitable for most mid latitudes in the northern hemisphere. If in the southern hemisphere all that is required is to change round the phasing cable so the antenna pattern will be north phasing. The phasing cable has the effect of producing a larger gain on the south facing antenna pattern with a more elongated shape, also it has the effect of lowering the altitude at which the maximum gain is achieved.

Figures 7.9, 7.10, 7.11, and 7.12 are screen shots from the computer program “Radio Jupiter Pro” (this program will be covered in more detail later). It will be easier to explain the antenna patterns and the effect of the height at which they are used by reference to these screen shots. Looking at the first Fig. 7.9, the antenna pattern is the ellipse shape in the middle. The two horizontal lines in the middle represent the two di-poles, and the cross in the very center is the point of maximum gain of the antenna in this configuration. Jupiter can be seen just inside the antenna pattern bottom center and the Sun can be seen on the left hand side. The Sun’s track across the sky is the line below the antenna pattern, but in mid-summer if the Sun reaches 60 degrees or more above the local horizon during transit this configuration would work well.

Looking at the next Fig. 7.10, this has the 135 degree phasing cable in place. Nothing else has been changed; the antenna di-poles are still the horizontal lines in the middle of the image. But look how the shape of the antenna pattern has been changed by fitting the phasing cable. Notice the cross in the center of the ellipse, where the maximum gain of the antenna is in this configuration, the maximum gain is at 50 degrees above the local horizon, but look how close it is to Jupiter. This antenna configuration would be suitable for receiving radio emissions from the planet. Also notice the track below Jupiter, that is of the Sun. The configuration would also work very well to tune in to the radio emissions from the Sun.

Looking at Fig. 7.11, the only variable that has been changed is the height of the antenna, which is now 4.5 meters (15 feet). In this configuration the maximum gain will be at 40 degrees above the local horizon. Look how far Jupiter has been moved away from the center. This change could make all the difference to either receiving radio emissions or not. The Sun fares slightly better in this configuration at this time of the year (August).

The next Fig. 7.12 is of the antenna pattern with the antenna set at a height of 6 meters (20 feet). At this height the maximum gain from the antenna will be at 30 degrees altitude above the horizon. If Jupiter is low in the sky, as it has been in the last few years, this antenna configuration would get the most gain from the antenna. As the Sun makes its familiar rise and fall in altitude in the sky over the course of a year, from its highest position in midsummer to its lowest position in midwinter, the height at which the antennas are used will need to be adjusted, to keep the object, either the Sun or Jupiter, as close to the center as possible to get the most gain from the antenna.

Why must the object be kept at the center of the antenna pattern to get the most gain? Surely if the object is within the antenna pattern the receiver should be able to pick up the radio emissions. To explain this, switch on a flashlight inside a dark room and there will be directly in front of the flashlight a fully lit area of light projected on to a nearby wall, but all around this fully lit area will be a semi-lit area. Think of this semi-lit and fully lit area as the antenna pattern or beam. If we take Jupiter as the example, when Jupiter is completely outside the antenna beam we can’t see it as its in darkness, neither can the receiver, but as the Earth rotates and brings Jupiter across the sky into the antenna beam it first enters the semi-lit area, so in theory the receiver could pick up radio emissions from the planet but the gain from the antenna will be lower, and as Jupiter makes its way into the fully lit area of the beam this is where we get the most gain and this is the best time to listen for radio emissions.

As the rotation of the Earth now moves Jupiter out of the fully lit area on the opposite side of the antenna beam, we start to lose the gain of our antenna once again. Note that the ellipse used to indicate the antenna pattern is a theoretical depiction of the antenna pattern and it is not set in stone. It is therefore best to start listening an hour and a half to 2 hours either side of the transit time marked on the antenna pattern. This is the best chance to pick up the radio emissions. There is a way around this problem by using a different antenna design, and there are a number of different types available on the market, such as the steerable high gain antennas like a three element Yagi. But this will bring its own problems as they will need an antenna mast to mount the antenna and a suitable way to steer the antenna, as these type of antenna are highly directional and will need moving every hour or so, not to mention the cost of such an antenna and the steering device.

7.5 Software

Included within the Radio Jove receiver kit are two computer programs, “Radio-SkyPipe” and “Radio Jupiter Pro”. Both are the creation of Jim Sky of Radio Sky Publishing, www.radioskypublishings. Radio-SkyPipe is a very useful program and easy to understand and use. Once loaded onto the computer, it turns the computer into a chart recorder with an on-screen display similar to the old paper chart recorders, but without generating miles of paper tracings. The version supplied has some of the utilities blocked, but it is a useful starting point, and this is enough to get the receiver up and running and will give a visual display of the output of the Radio Jove receiver. Depending on the operating system of the computer, some of the input characteristics on the computers audio input settings will need to be set manually, in a similar way as described within the chapter on the SuperSID monitor, or if a more modern operating program used this may be done automatically by the computer. A window will pop up asking if microphone or inline input is required, check the inline box and if possible mute the microphone input.

Soon it maybe found that the supplied version of the program has outgrown its usefulness and the fully functioning version is required. If wishing to purchase the fully functioning program from the Radio Sky website, which is thoroughly recommended, it can be easily downloaded over the internet. Once payment is received an email will be sent with a code, and once this code is entered into the program it unlocks the rest of the program’s functions. After purchasing the program, any updates and improvements made to the program are free to download and install, so it is always possible to have the up-to-date version of the program. The fully functioning program has lots of useful functions, far too many to be discussed here, but it is worth pointing out a few. The program is capable of recording sound files, and playing them back, also it is programmable so it can be triggered automatically to record sound if a level set by the operator is exceeded. It has a calibration wizard function that can be used with the 2080 calibrator, in order to calibrate the program to the Radio Jove receiver. The on-screen instructions are clear and easy to follow (this will be covered later in the chapter). Any files will automatically be saved and can be easily retrieved later. Through the program the computer’s sound card can be accessed, to change sampling rates, etc.

Once Radio-SkyPipe is running, a small control panel will be shown in the top left of the screen. By simply clicking one of these buttons a large range of tasks can be performed, such as changing the scales of the display or a record button which will immediately start recording a sound file. If seeing or hearing something of interest notations can be added to the graph so it can be easily found later, or even save the screen display straight to a file for retrieving later. To sum up, this is a very versatile program and it is very good at what it does, it is easy to use, although some aspects of the program may take a little practice to master.

The other piece of software is one of those things that comes along and makes one wonder how life went on before without it. Radio Jupiter Pro is one of these things. The version supplied with the Radio Jove kit has some of the functions blocked as with the previous program. This is fine as an introduction, though this too will soon be outgrown, and the fully functioning program will be required. This is also downloadable from the Radio Sky website, using the same procedure as described with the previous program. As with Radio-SkyPipe, once the software has been purchased any updates or improvements made to the program are free to download and install, so the latest version will always be available to work from.

The fully functioning Radio Jupiter Pro software has everything needed for observing Jupiter and the Sun using the Radio Jove receiver. Once the software has been loaded there are a few things that need to be set, latitude and longitude, plus preferred date format and time zone the program then does the rest. On opening the program a window pops up showing the relative position of Jupiter and the Sun plus the time and date. At the bottom of the window is a smaller window that informs the user if there is a possibility of any radio noise storms from Jupiter happening at that moment. Click on the next window and the “radio storm prediction” window pops up. This window displays a chart showing the predictions for radio storms for the next 24 hours. There are buttons to skip to the next day or so into the future or the past. The predictions are also displayed in written form, giving approximate start and finishing times. The Sun’s visibility above the horizon is also shown. Moving the computer’s curser across the screen the details of the time will be seen to change according to the curser’s movement, and the positions of the Sun and Jupiter will be shown in degrees of altitude.

The next window is the “Io phase plan”. This charts Jupiter and the central meridian longitudes, and gives a probability of receiving a radio storm if Jupiter is in the right part of the sky for the observer. Looking at the Fig. 7.13, a screen shot of this particular window. This image may seem strange at first sight, but it is quite straightforward to understand once a number of key features are pointed out.

Looking at the image, Jupiter can be seen on the right hand side just below center. The lines running from left to right at an angle are Earth times in 24 hours. As Jupiter moves along these lines the probability of picking up a radio storm can be seen to change. Looking on the left hand side of the image there is a color-coded strip, starting with black at the bottom and red at the top, there is also a percentage value marked at different points along the strip to give the user an idea of the chances of picking up a radio storm. Moving the computer curser across the screen the probability can be seen to change on the right hand side of the image.

The Io phase window can be useful, because as Jupiter moves along the time lines, the probability of receiving radio emissions from Jupiter can be seen at any point. As the planet will be seen to cross the different colored areas, the brighter the color the greater the chances of receiving radio emissions. Ideally Jupiter wants to be in the red area just as Jupiter is passing through the center of the antenna beam. The next window is the antenna pattern window. Recalling the screen shot images from the section covering antenna configurations, this is what this particular window looks like. This part of the program is great for knowing the correct time to listen to the Sun and Jupiter, and gives a visual indication of the positions of the Sun and Jupiter within the antenna beam. The program comes with a number of pre-loaded antennas ready for the user to load the particular one they are thinking of using. This can be good, as it can be seen which configuration is the best for the location, or if coming up with an antenna configuration of their own this can also be loaded into the program. By moving the computer curser around on the map the altitude and azimuth coordinates can be seen to change in the top left hand side of the screen, and this is extremely useful for doing a quick check on the altitude of the Sun and Jupiter.

Choose to personalize the screen, by having stars on the background down to magnitude 5, or another magnitude set by the user to match their own location. This could be useful if having trouble finding Jupiter in the sky. Choose to have the galactic plane shown on the map. This particular part of the sky is rather noisy at radio wavelengths, and contains some of the “brighter” radio sources, as it follows the Milky Way across the sky. This is where Karl Jansky discovered the radio noise coming from the galactic center in the early 1930s from the powerful radio source “Sagittarius A” in the constellation of Sagittarius. The tracks of the Sun and Jupiter are also shown and either one can be switched on or off if one chooses. One good feature about this window is that it keeps updating itself, and the progress of the Sun and Jupiter can be watched through the antenna beam while carrying out radio observations.

The next window, the “altitude vs. azimuth” window, simply shows the altitude and azimuth track of the Sun and Jupiter across the sky. Use this window to carry out checks of the altitude of the Sun and Jupiter, in order to gain the best antenna configuration to get the maximum gain from the antenna. The next window is the “ephemeris” window, and this shows a table giving the predicted positions of the Sun and Jupiter at given intervals and can be set by the user if need be. The next window is the “plot Jovicentric declination of the Earth” window. This window shows the relative position of the planet Jupiter in the sky over any year the user chooses to set. This has been useful in recent years while waiting for Jupiter to return back into the northern hemisphere tracking Jupiter’s progress making its way from the southern skies then crossing the celestial equator and making a welcome return into the northern skies again, ready for visual and radio observations.

The next window is the “yearly visibility schedule”. This window will calculate the best times to observe the planet Jupiter over a given year. For instance, the schedule will indicate when Jupiter will be above the horizon when the Sun has set. Its graph is quite easy to understand. Jupiter is shown on the graph as a cyan (blue green) color, and the Sun as the color yellow. If both are in the sky together the color changes to a light green, and if neither are above the horizon the color white will be seen. The months of the year run vertically down the left hand side and there are three hourly time lines running from top to bottom. Using this window it can be seen instantly the best months of a year to observe Jupiter. A word of caution, which may be less of a problem nowadays with the speed of the modern day processors on computers, but is still worth mentioning. There are two settings on this particular window, “high resolution” and “low resolution”, and if using a reasonably fast computer leave the setting on “high resolution”, if using a slower machine use the “low resolution” setting. Trying to use the “high resolution” setting on a slower computer it may take several minutes to produce the graph.

The next window is the “observer’s log”. This is an especially likable part of the program when listening in person as well as when recording the output from the Radio Jove receiver on Radio-SkyPipe. On hearing a radio emission there is no need to scramble around for a pencil and paper, while at the same time trying to look at the clock or watch to make a note of the time, then trying to write it all down for use later – all while holding a flashlight in the mouth. The “observer’s log” does all this, so we can get on with the job in hand and listen. The observer’s log window in its simplest form shows three different types of radio storm signals: “S” bursts, “L” bursts and undetermined. Each one is divided into three different strengths: weak, medium, and strong. On hearing a radio emission, for example a medium “S” burst, just click on the medium “S” burst button and the program will do the rest. It will log the type of emission, the time and date, and save information about the position of Jupiter in the sky at the time of the storm. This can then be saved to a file and studied later or printed out to give a permanent copy of the observation.

The final window in this very useful program is the “automated action parameters” window. This allows the user to set specific conditions and tasks for the program to perform, for example to look for a particular type of Jovian storm at a specific date and time, and then make the user aware of this.

7.6 Calibration

Although the Radio Jove receiver will work without being calibrated, and any radio emissions received are still good, to some extent they will be useless as they cannot be compared with any other observations made by other Radio Jove users. To give an example of this, think of the mess if cars were sold without speedometers, it would be impossible to enforce a speed limit. This is why car speedometers are calibrated. This is also true with the Radio Jove receiver. It helps if everyone is using the same unit, as mismatching of units can prove very expensive not to mention very embarrassing for all concerned. A cautionary example springs to mind. Contractors building parts of a Mars Climate Orbiter for NASA made the mistake of employing one company working in imperial units, to design the descent engine to switch off at X number of feet, the other working in metric units programmed the descent engine computer to switch off at X number of meters. So the space probe was three times the height it should have been when the descent engine switched off leaving the space probe to crash on to the surface of Mars. This makes a good case for everyone’s Radio Jove receiver to be calibrated in the same way and using the same units.

In radio astronomy the term “antenna temperature” will keep coming up. Antenna temperature is used as a measure of the power per unit of bandwidth of the antenna, and is measured in degrees Kelvin. This can require some serious mathematics to explain fully, therefore a thorough explanation goes beyond the realms of this book. To keep it simple, the antenna temperature is not a physical measure of the antenna temperature itself, but more of a measure of radio energy the antenna is receiving from a radio source. For example, the calibrator discussed below simulates an antenna temperature of 25,000 degrees Kelvin into the Radio Jove receiver. Think of temperature as not being either hot or cold but as a measure of the energy at which atoms themselves vibrate or move. At absolute zero, or zero degrees Kelvin, all the vibrations and movements within the atoms of a material stop. These atoms have no thermal energy left. The Sun’s outer atmosphere or corona has a temperature of around two million degrees Kelvin. If it were possible to measure the physical temperature of the corona with a thermometer we would probably freeze to death trying to do so if the Sun wasn’t nearby. The Sun’s corona is so rarefied and the atoms so far apart there is no physical heat. However, the energy within the movement of these atoms of the corona would be around the two million degree mark.

To calibrate the Radio Jove receiver we need to input a signal of a known quality and power in order to calibrate the Radio Jove receiver to the program Radio-Skypipe. A way to do this is to use the RF-2080 CF. Please see Fig. 7.14.

This item can be ordered at the same time as the Radio Jove kit. It is supplied ready-built and comes in two different types. The first is the RF-2080 C. This particular model only has the calibration unit fitted. This is a good chose if living in a radio quiet site, but for most of us the RF-2080 CF will prove a better purchase. This particular model also has a narrow band radio filter fitted alongside the calibrator section of the unit. This filter has proven itself useful in blocking some of the radio interference from some observing sites. There is a down side to this filter, a small loss of signal strength from the antenna to the receiver due to the internal circuitry of the filter. The up side is that the benefit of the filter outweighs this small signal loss.

The calibrator is fitted between the antenna and the Radio Jove receiver. When the calibrator is switched on it introduces a white noise signal of a known quality and power (25,000 degrees Kelvin) into the Radio Jove receiver. Using the program Radio-SkyPipe, click onto the tools tab at the top of the screen and scroll down the list, the last on the list is the calibration wizard. Selecting this starts the calibration process. There are a number of on screen instructions all of which are quite easy to follow. Once carried out, the program Radio-SkyPipe will automatically carry out the calibration. When done, unless the volume control on the Radio Jove receiver is altered, the calibration will hold fast. If the volume control is moved, then the calibration wizard will need to be run again. This is why a volume control on the headphones is desirable, as not to disturb the calibration. Once calibrated to the Radio-SkyPipe, it will be possible to gain an insight to whether the observing site is “radio” quiet or not.

As mentioned above, the calibrator simulates an antenna temperature of 25,000 degrees Kelvin. This is generally considered to be a radio quiet site. Operate the switch on the calibrator this will switch off the calibrator and switch back to the antenna itself, if there is not a large increase in noise then this is a radio quiet site in which to observe, and there should be no problem in receiving radio emissions from Jupiter or the Sun. If there is a large increase in noise when switching back to the antenna, this indicates a noisy radio site. Don’t worry, all is not lost. If a trace on Radio-SkyPipe is started this will give an indication of the level of background noise at the observing site.

A good idea is to leave the Radio Jove receiver and Radio-SkyPipe running over the course of a few days and a pattern within the trace itself may start to be seen. Look for times when there are few spikes on the graph, these are interference or from lightning. Interference can come from almost any electrical device, but some are worse than others. It has been found that the interference from such electrical devices reduce from around midnight to about 5 am, when everyone has switched off their television sets and gone to bed. It is not uncommon to get the odd spike of interference now and again from heating thermostats, especially on cold nights. Having a background level which is constantly above 750,000 degrees Kelvin means that there will be very little chance of picking up the planet Jupiter. The radio storms from the giant planet don’t exceed this level, try and find a quieter site for the antenna. Other Radio Jove users have found moving their antenna only a short distance from its original location and this has been enough to make all the difference. Either way, it should still be able to pick up the radio emissions from the Sun as these can reach levels of several million degrees, depending on the level of background interference, some of the weaker radio emissions from the Sun maybe missed.

If lucky enough to have a quiet site, run the Radio Jove receiver over a number of days, it may be noticed that there is a rise in the background levels on the Radio-SkyPipe graphs. This will appear to be happening roughly at the same time each day. On closer inspection it may be noticed that this is happening 4 minutes earlier each day. This rise in the background level is the same phenomenon Karl Jansky picked up with his merry-go-round antenna in the early 1930s, the galactic center in the constellation of Sagittarius. One Radio Jove user has even picked up a pulsar using their equipment.

7.7 Radio Emissions from the Sun

The first person recorded to try and detect radio emissions from the Sun was Thomas Alva Edison. This is the same Thomas Edison famed for many inventions, such as the light bulb, phonograph, the telephone transmitter and the electric chair. Edison tried to detect radio emissions from the Sun in the early 1890s with his laboratory assistant. Descriptions of the construction of the antenna record that it was made up of coils of wire wrapped around a metallic core, possibly one of wrought or cast iron, but no records are known to exist of any radio emissions having been received. The reasons for Edison’s failure to receive radio emissions could be due to a number of factors, such as the possibility that he was trying at the wrong frequency or that his equipment wasn’t sensitive enough for the job. It could be that he chose to try it at solar minimum, when the chances of receiving radio emissions were at their lowest. Whatever the reason for the failure, Edison didn’t take it any further.

The next recorded person to try was Sir Oliver J. Lodge. He made his attempt between 1895 and 1900. He had built himself a more sensitive receiver and antenna then Edison had used, but even this wasn’t sensitive enough to detect the Sun’s radio emissions. There are records of other observers who tried and failed over the years to receive radio emissions from the Sun. It wasn’t until the existence of the ionosphere was proven in the 1920s, when its effects on different radio frequencies was starting to be understood, that it dawned on observers that they needed to use the correct frequency, i.e. one that the ionosphere would allow to pass through it in order to pick up radio emissions from the Sun.

By now the 11-year solar cycle was beginning to be understood, but as yet no one had made the connection between solar activity and radio emissions. Skip forward to the 1940s and the outbreak of World War Two and the first attempt by the British to use their new invention of radar. In 1942 the British had built up what was known as the “chain home stations-radar cover”. This consisted of a large number of radar instillations that covered the entire length of the east coast of the United Kingdom, from the most northern part of Scotland all the way down the east coast and most of southern England. Some of these radar stations reported receiving a strong signal that seemed to be jamming the operation of the radar at particular instillations. The signal seemed to be coming from the east, over mainland Europe. This was a cause of great concern, as it was first thought that the enemy had managed to develop a new piece of equipment that was powerful enough to produce a signal capable of jamming some of the British radar instillations. This would have made the radar all but useless at warning against an attack from the air.

J.S. Hey, whose wartime job was to be part of the operational research group studying the effectiveness and efficiency of the new radar system, undertook a detailed examination of all the radar equipment. When they found it was working correctly their attention then turned to the signal that had been received. They found that at the time the jamming signal had been picked up the Sun was positioned low in the sky over mainland Europe. This lead Hey to come up with a theory that the jamming signal wasn’t from the enemy but, could be radio emissions coming from the Sun. Astronomers observing the Sun had noted that a large group of new sunspots had recently appeared on the Sun’s disc. Hey’s theory was correct. What the radar operators had in fact received was radio emissions from the Sun caused by the increased solar activity. This then made the link between solar activity and radio emissions from the Sun.

Unlike the planet Jupiter, where radio emissions can be predicted with a certain amount of accuracy, the Sun is a law unto itself. Take for instance the lead up to the 2012 solar maximum, which was very slow in coming. After observing the Sun for weeks during the summer of 2011 observers saw very little in the way of activity. It has now been suggested that the 2012 solar maximum will not happen until late 2013 or early 2014, and solar astronomers have gone as far as saying the next solar maximum, due around 2024, may be even worse; time will tell. The Sun has done strange things in the past. For example, the Maunder minimum around the year 1715, where solar activity was low for about 70 years. It has been suggested that the total energy output from the Sun also dropped in these years. This reduced output from the Sun has lead experts to suggest that this caused the river Thames in London to freeze every winter, to such an extent that an open air market and fair could be held on the frozen river.

The theory of the Sun randomly reducing its overall output in the past years has also been linked to large rivers reducing their flow in the years when the solar activity has been low. In other parts of the world other rivers have exhibited the opposite effect, and when solar output returns to normal so do the river levels. Solar activity can play an important role in the radio emissions that the Sun generates. Radio emissions from the Sun come randomly, although when sunspots can be seen this is a good indication that there will be some radio emissions. Larger sizes and numbers of sunspots usually mean more radio emissions, but the Sun has thrown out the odd surprise now and again. Radio emissions from the Sun can come in several different forms and over several different frequencies. Depending on which source of information used the description of each type of radio emission can vary very slightly. The following list has been compiled from many different sources, and common ground has been found from each different description:

1.
Quiet Sun: This is taken to mean a low level of solar activity, with little or no sunspots visible, and with X-ray emissions that are below a C class flare. Other radio emissions are continuous across all wavelengths and originate from thermal radiation. For example, the Sun at solar minimum.
2.
Type 1: A noise storm composed of many short bursts, from a tenth of a second to fifteen seconds. They are of variable intensity and may last for many hours or days.
3.
Type 2: (Slow drifting bursts) These bursts are caused when a shock wave from a large flare travels up through the Sun’s atmosphere. The shock wave is caused by material being thrown off by the flare. They are of narrow band emission and slowly sweep from high to low frequencies over several minutes.
4.
Type 3: (Fast drifting bursts) These bursts are narrow band and drift rapidly from high to low frequencies over several seconds. They are associated with active regions of the Sun’s surface, for example a solar flare or large sunspot.
5.
Type 4: Continuum emissions can last from many hours, and are associated with major flare events, beginning soon after the flare has erupted and reaching its maximum intensity.
6.
U-burst: Sometimes called Castelli-U, they can last for several seconds and the wavelength changes rapidly, decreasing and increasing again. They are often associated with flares and have a similar origin as Type 3 active regions on the Sun’s surface.

Although the above are different types of radio emissions, some occur more frequently than others, and for our purposes the characteristics of each do not need to be known. It takes an experienced person, far more experienced then the author, to tell the difference. It space is an issue two examples of solar activity are shown in the Figs. 7.15 and 7.16. These have been received by the author using the Radio Jove receiver with its dual di-pole antenna and using the program Radio-SkyPipe.

This image Fig. 7.15 is a Type 3 burst note the shape is like a shark’s fin. Note also the rapid rise (the almost vertical line on the left hand side) and the slow return to background again (the shallow angled right hand side).

The image Fig. 7.16 is of a triple Type 3 burst.

Both images are of one particular type of solar activity. It is highly recommended that one visits the Radio Jove website where there are far more examples of other types of solar activity, along with audio records made of the Sun using the Radio Jove receiver.

7.8 Radio Emissions from the Planet Jupiter

Radio emissions from the planet Jupiter were discovered accidentally in 1955 by B. Burke and K. Franklin of the Carnegie Institution in Washington, DC. The two observers were carrying out experiments using a new type of receiving antenna. This antenna was designed to work at a frequency of 20 megahertz. When the receiver and antenna were switched on they picked up all sorts of signals, both wanted and unwanted. The unwanted parts were thought to come from the usual sources of interference. By the process of elimination the two observers worked their way through each of the unwanted signals and either removed the sources of interference or made allowances for them on the receiver’s output chart. But still there was an irritating signal that seemed to come and go with no particular pattern. The two observers thought this random signal may come from the sparks generated by vehicle ignition systems. Then it was noticed that although the interference didn’t happen every day it did happen at roughly the same time of day when it did. They made recordings of the interference and tried in vain to track down its source. After they had exhausted all possible sources of interference the two observers then thought the interference was possibility more extraterrestrial than terrestrial. But from where?

Planets at that time weren’t even on the list of targets for a radio astronomer. Further studies found that the planet Jupiter was within the beam of the antenna every time the interference was received. So their attention turned to Jupiter, and to their mutual surprise Jupiter was indeed found to be the source of the interference. The question of how the planet produced these radio emissions was the greatest mystery. Due to the sound of the interference it was first thought that it could be lightning discharging high within the Jovian atmosphere. It was an excellent piece of detective work on the part of Burke and Franklin, and full credit to them both. A few years earlier, in Australia, the same type of interference was picked up at the frequency of 18 megahertz, but the connection to the planet Jupiter wasn’t found.

Unlike the Sun, which follows the same path through our skies each season of the year, Jupiter can be anywhere in the sky within a short distance north or south of the ecliptic. The ecliptic being the line the Sun traces through the sky over the course of a year. In recent years Jupiter has been in the southern hemisphere, which is great if observing from the southern hemisphere, but for observers in the northern hemisphere this has proven a bit of a challenge for the Radio Jove observer. This is because the antennas need to be double the usual height required when Jupiter is in the southern skies, in order to get enough gain from the antenna to receive the radio emissions from Jupiter.

Anyone familiar with using an optical telescope will know through experience that unless the “seeing” is very good it is not worth bothering to attempt to observe objects within approximately 15–20 degrees or so in altitude of the local horizon. This is due to the fact at this altitude we are looking through the greatest thickness of the Earth’s atmosphere, and this part of the atmosphere contains all of the light pollution and the pollution from industry, it also contains a lot of dust (especially when an Icelandic volcano erupts) which can produce some nice sunsets. This can be also true with radio astronomy. The radio waves must travel through this greater thickness of atmosphere, and they can also suffer in the same way as optical light, although radio waves suffer to a lesser degree then optical light. So it is a case of waiting for Jupiter to get in to the right position for observation with the Radio Jove receiver, in the same way as with an optical telescope.

When viewing optically the “seeing” is better if the object is at a high altitude as viewed from an observing site, and also when the object is at opposition. At opposition an object is usually at its closest approach to the Earth at the same time as it reaches opposition. This is more or less the same when observing Jupiter with the Radio Jove receiver, although more experienced Radio Jove operators agree that a month or so before the planet reaches opposition is actually the best time to observe using the Radio Jove receiver. Although this may be the ideal time to view, as long as the Sun is below the horizon and the ionization in the ionosphere is at a low level it should be possible to receive radio emissions from Jupiter.

Radio emissions from the planet Jupiter are divided into two types, with the first known as an “L” burst, the “L” standing for the word “long”. These L bursts have a sound like gentle waves from the sea washing up on a sandy beach. Their sound has also been described as like a breeze blowing through a leafy tree. The second type of radio emission from the planet Jupiter are the “S” bursts, with the “S” standing for the word “short”. These have been likened to the sound that hailstones make raining down onto a corrugated metal sheet or roof. Some refer to the noise of an “S” burst as sounding like the sizzling of a rasher of bacon when it is first placed into a hot frying pan. Both these sounds can be heard separately or together, but they are always heard with the white noise sound which is the sound of galactic background radiation.

If using the Radio-Jupiter Pro program it should be possible to identify which type of radio storm is received. There are three basic types of radio storm, and these are called A, B and C. These originate from different latitudes from within Jupiter itself, although we need not go into too much detail about the origins of these here, as a whole book could be dedicated to this subject. As Jupiter spins on its axis these different zones move through Jupiter’s powerful magnetic field generating the radio emissions. Io, the innermost moon of Jupiter, plays a part with the radio emissions from the planet, and this is known as the Io effect. As Io orbits around Jupiter it produces a cone-shaped area in front of the moon itself. This cone is made up of charged particles, and is a type of plasma. This has the effect of creating a beam which concentrates the radio emissions, in the same sort of way that a lighthouse concentrates a beam of light. As Io orbits Jupiter, if the cone or beam of radio emissions points in the direction of the Earth, there is a greater chance of receiving these emissions. These storms are known as Io A, Io B and Io C. Some of these radio storms are more predictable and are of a stronger intensity than others. It is suggested to start with the more powerful storms and then try for the more unpredictable and less powerful ones, having gained some experience in their detection. A good place to start is with Io B and Io C storms, as these can be quite strong in nature. These are made up of mostly “S” burst activities, although this is not cast is stone and “L” bursts may be heard at the same time. The not so powerful storms are the Io A and the non-Io storms. These mostly consist of “L” bursts, but as before it is possible to pick up the odd “S” burst here and there.

The radio storms from Jupiter can be predicted with a certain amount of accuracy. Although it is sometimes found even if Jupiter is in the right part of the sky, in the center of the antenna beam, and Radio-Jupiter Pro is indicating that an Io B storm is taking place, the receiver is picking up absolutely nothing. This doesn’t mean there is anything wrong with the equipment or the software. There are many factors that can stop the radio emissions getting from Jupiter to the antenna. The ionosphere may still be partly ionized, especially if solar activity is high. This ionization usually makes itself known by the large number of stations the Radio Jove receiver is picking up. It is also possible that the aurora has decided to put on a show and is playing havoc with the atoms in the upper atmosphere. It may even be something as simple as Jupiter deciding not to go along with the observing plan. Whatever the reason, it just means luck wasn’t in that particular night. Be prepared to be surprised by Jupiter now and again. For instance, nothing may be shown on any of the predictions but the receiver is picking up quite a good number of “L” and “S” bursts.

Limitations on space and the large number of different factors involved with these type of radio storms from Jupiter, such as length of duration of each storm, the intensity and strength of each storm, also the varying types of storm, it is strongly advised to visit the Radio Jove website, and once there to follow the links to the Radio Jove archives. At the Radio Jove archives there are lots of excellent examples of Radio-SkyPipe images of both the Sun and of the planet Jupiter. This archive is also a good starting point to familiarize oneself with what to look for in relation to both the Sun and Jupiter. The images may at first seem to look all the same to start with, but soon familiar patterns will be seen forming, especially from the Sun. While at the Radio Jove website audio recordings of the planet Jupiter will be found.

7.9 References for More Information

If only having the remotest interest in receiving the radio emissions from the Sun or the planet Jupiter, a good starting point should be the second edition of the book “Listening to Jupiter” by Richard S. Flagg, published by Radio-sky in 2000 (if a copy can be procured). Flagg’s excellent book is dedicated to the study of the Sun and Jupiter by radio, covering all aspects of the study of the Sun and Jupiter by amateur radio equipment, not just the Radio Jove receiver. There is a full chapter discussing the Radio Jove project which goes into more detail and there is some mathematics involved. The book is written in a very readable way, with some excellent anecdotes.

The above book and all the computer programs discussed within this chapter, plus many other resources such as books and computer software, are available from Radio-Sky publishing at http://radiosky.com. Even if choosing not to go down the Radio Jove path, it is well worth a visit.

Another excellent website is the Radio Jove Project website at http:/radiojove.gsfc.nasa.gov/. From this site it is possible to find out all about the Radio Jove project, and download newsletters. The newsletters are full of information about any forthcoming events and they include images of Radio Jove receiving sites from all around the world. Some of these images can make one feel quite jealous. It’s a good idea to download some of the older newsletters to see how much things have changed. Hear samples of the radio emissions from the Sun and Jupiter, and also hear examples of the galactic background radiation and some of the common sources of interference. Find Radio-SkyPipe images of the different types of radio emissions from the Sun and Jupiter, and those interested can download and print the order form for the Radio Jove kit from here. There are links to other websites of interest.

Another useful website is http://www.swpc.noaa.gov/ftpdir/indices/events/events.txt. This site produces a list in simple text format that relates to the solar activity for that particular day. If one thinks a solar flare or other radio emission has been captured, simply check this site and the particulars of the flare can be identified. Take a good look around this site as there is lots of information and a glossary of terms used in solar radio astronomy.

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Steven Arnold

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Arnold, S. (2014). The NASA Radio Jove Project. In: Getting Started in Radio Astronomy. The Patrick Moore Practical Astronomy Series. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-8157-7_7

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DOI: https://doi.org/10.1007/978-1-4614-8157-7_7
Published: 15 August 2013
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