INTRODUCTION
BUILDING THE TELESCOPE
  
SOFTWARE
  
OBSERVING 
 | 
DATA PROCESSING 
 | 
 

Radio Telescope – Building & Testing the Radio JOVE Radio Telescope

The JOVE radio telescope comprises a receiver and antenna that operates over a narrow range of short-wave frequencies centered on 20.1 MHz (megahertz). The receiver contains over 100 electronic components and pieces of hardware. Fabrication will include the handling of small, delicate, electronic parts, most of which will be mounted and soldered on a printed circuit (PC) board.

You will also construct the dual dipole antenna. A coaxial transmission line carries the radio signals from the antenna to the receiver. If you intend to make scientifically useful measurements you may enhance the basic radio telescope with the optional RF2080 calibrator.

Fabrication of the radio telescope is covered in detail in the receiver and antenna construction manuals. The receiver manual contains assembly instructions including tune up and troubleshooting procedures. If you have difficulties in successfully completing the receiver the Radio JOVE staff are available to help. As a final resort you can send the receiver to a Radio JOVE staff member who will get the unit working for a nominal fee.

Download the Construction Manuals

Testing the Completed Kit

Testing the Receiver and Antenna Together

Note—do not do any testing of the receiver and antenna if there is nearby lightning.

We will cover 3 different levels of testing:

  1. Basic Test: hooking the receiver up to the antenna and listening for an increase in background noise.
  2. Second Test: connecting the receiver to a computer running SkyPipe software.
  3. Third Test [optional]: using the optional RF2080 calibrator to determine the background antenna temperature.

1. Basic test (Antenna and receiver)

The simplest test is to listen for an increase in the background noise from the receiver when the antenna is connected to the receiver. You can do this test either with a single dipole or the completed dual dipole antenna. Before connecting the antenna to the receiver, set the receiver audio gain control between the 12 and 3 oclock position. You should hear a slight hissing sound in the headphones. With the antenna connected, the static sound should increase significantly and be very easy to hear. (You may want to take off your headphones while the antenna is being connected, as there is usually a loud crackling sound as the antenna connector is being screwed on).

You may hear stations as you tune the receiver to different frequencies. If there is no increase in the background noise when the antenna is connected, check connections and connectors between the antenna and receiver. If you do not hear a significant noise increase there is a short or open circuit in the antenna wiring or the receiver is not working correctly. You can trouble shoot the antenna by hooking up the individual dipoles directly to the receiver (bypassing the T power combiner). If either dipole individually produces the desired receiver noise increase then the problem must lie with the other dipole, the power combiner, or the lead-in coax. If you are unable to obtain the noise increase with either dipole individually, or connected together as a pair, then the problem must lie with the receiver.

The noise that you hear with the antenna connected should have a steady hissing static sound (except for stations and an occasional static pop or crash). If there is a raucous buzzing sound (which may be intermittent) it is probably due to either arcing on a nearby power line or perhaps you are using a "wall wart" power supply that is poorly regulated. It is important that the power supply, which you use for the receiver and speaker system, produce a clean DC voltage. The recommended power supply is either a 12 volt battery or the Jameco (www.jameco.com) part number 162996.

2. Intermediate test (Antenna, receiver, computer)

For this test you will connect the receiver audio output to an audio input jack on your computer. This connection is best made using a stereo audio cable connected to either audio jack on the rear of the JOVE receiver. You must be using a Windows computer (or perhaps a Mac with a windows emulator). Install the latest version of SkyPipe (you will receive Skypipe download instructions when you purchase the JOVE radio telescope kit.) Before running this test familiarize yourself with SkyPipe by reading over the instructions at
http://www.radiosky.com/skypipehelp/V2/skypipehelpindex.html.

You can get headphone audio from the unused audio jack on the rear panel of the JOVE receiver or speaker level audio from the computer sound system.

If you are using a laptop computer there may only be a microphone jack and if you are using a desktop computer there may be both microphone and line level audio input jacks. Laptop audio input jacks may work best if you do not use the sometimes available audio boost software. We have had some reports from laptop users that the internal microphone does not disconnect properly and so audio from the computer microphone gets connected as the signal source for SkyPipe. As a general statement a desktop computer line input is preferred.

Having made the audio connection between the receiver and the computer, the next step is to set the computer audio input as the input signal source for SkyPipe. The procedure varies slightly depending on your Windows operating system.

In Widows10 start by right clicking the speaker icon in the lower right of the home screen. Select Open Sound Settings. On the next screen you should find a path to the Sound Control Panel where you should select the Recording option and choose the option appropriate for your JOVE receiver audio connection.

screen shot of software interface

Open SkyPipe and select Options. Under Options, click the tab Sound. The PC sound card should be listed under Device. The input source is where you plugged the audio line from the receiver to the PC. Click on Data Source in the Options panel of SkyPipe. Chanel 1, should be set to Sound Card Left. Save all and close the Options panel. If it becomes necessary to manually adjust the input levels that can be done through the sound control panel. Select the input source (with the green check). Click on Properties. Under Properties select, "Levels".

Once you have SkyPipe running and the antenna connected make sure that you can use the receiver volume control to adjust the background signal level up and down. Return the volume control to 12 oclock for solar observations or 3 oclock for Jupiter observations. A typical SkyPipe strip chart presentation during the daytime is seen below. At night time you will see a flatter (more constant) background noise level with fewer stations.

Skypipe chart example

You should see a significant increase in the background trace when the antenna is connected. The trace should rise sharply as you tune across stations. The SkyPipe trace is normally set at a level of around 1000 on the SkyPipe vertical scale with a trace thickness of about 1/8 of an inch. The trace level on SkyPipe is set using the receiver volume control in conjunction with the software record volume control found on your computer. It is important to note that the vertical scale numbers on the strip chart above are in SkyPipe units (SPU) and are simply relative numbers related to the strength of the audio signal from the JOVE receiver- they are not absolute numbers such as volts or watts. In order to obtain scientifically useful measurement of signal strength we must calibrate the receiver (using the optional RF-2080 calibrator or equivalent).

With the antenna connected you should hear the hissing sound of background static (this is galactic background radiation caused by relativistic electrons spiraling in our galactic magnetic field). You may also hear additional signals due to terrestrial sources. As you tune the receiver dial you may hear stations. When listening for Jupiter or the Sun you should tune to a clear frequency between the stations. You may also hear pops and snaps due to distant lightning. (If there is nearby lightning disconnect the antenna from the receiver).

3. Final Test (Antenna, calibrator, receiver, computer)

At a radioquiet receiving site the background (baseline) noise is due primarily to emissions from the galaxy. However, signals from earth-based sources such as arcing power lines, computers, electric motors and aquarium heaters (and lots of other things) may be added to the galactic background noise. These noise sources are generally broadband in nature and you cannot tune the radio to avoid them. If the total noise background (galactic plus terrestrial sources) is too high, then signals from Jupiter and the Sun will be masked by the local noise.

In order to determine how quiet or noisy a receiving site is we need a calibrated noise source (the RF2080) that generates about the same signal level as the galactic background. When substituted for the antenna, the noise source establishes a reference signal level. If the level from the antenna is about the same as this reference, then the receiving site is quiet. However, if the noise level from the antenna is several times stronger, then we know the site is noisy and may not be suitable.

When the radio telescope is calibrated the vertical scale of SkyPipe will read in absolute units of antenna temperature measured in degrees kelvin rather than relative SPU. Details are provided in the RF2080 instruction manual.

To perform this test install the RF2080 calibrator between the receiver end of the antenna coax and the JOVE receiver as shown in the block diagram below.

block diagram of radio telescope components

With the RF2080 turned on run the SkyPipe Calibration Wizard. When the Wizard is done the SkyPipe chart will be calibrated in terms of antenna temperature.

At 20 MHz the normal temperature of the galactic background is between 25 and 100 thousand kelvin (25°K–100°K). If the nighttime trace is in this range your site is radio quiet. If your background temperature is higher than about 250°K you will likely detect only moderately strong Jupiter signals. Higher temperatures will make it difficult to detect Jupiter but your site may still be suitable for strong solar bursts.

examples of building the RJ 1.1 radio telescope

Soldering Techniques

Use only the recommended soldering iron (25-30 watts), preferably temperature regulated with a small tip. Keep a wet sponge near the soldering iron. KEEP YOUR SOLDERING IRON TIP CLEAN! When it gets dirty (black crud on tip), wipe the tip on the sponge.

When you solder, place the iron-tip in contact with the wire /component AND in contact with the printed circuit board (contact both at the same time). Another tip: to get the solder to start flowing after cleaning the tip, quickly melt a drop or two of solder onto the tip (called "tinning the tip") and then immediately apply the tip to the board/wire, heat both up and apply solder to the joint.

When solder flows smoothly and covers the joint remove the iron. The solder joint should be shiny, not gray and dull (a cold solder joint). This process should not take more than 5 seconds from grabbing the iron to putting it back in the holder. If you apply too much heat to the joint, the heat may damage a component.

You might practice soldering on an old PC board (preferably with holes in it). Try soldering scrap pieces of resistor leads to a terminal on the board until the connections look good. That way you can get a feel for how much heat is needed to get a good solder flow in a minimum period of time.

Recapping the soldering procedure:

  • Wipe the tip on the sponge.
  • "Tin" the tip with solder.
  • Apply the tip to both the component and the board.
  • Add solder to the joint (let the solder touch the board and tip)
  • Let the solder flow for a second or two.
  • Replace soldering iron. The new solder joint should be shiny (not dull).

View this how-to video on soldering: video title