MTM Scientific, Inc... Amateur Radio Telescope Plans

The Television Tuner sold by MTM Scientific, Inc can be used to build a simple amateur radio telescope for exploring radio astronomy. The Tuner will easily receive the frequency bands of 406-410 MHz and 608-614 MHz (UHF Channel 37) which are both recognized bands for making radio astronomy observations. The TV Tuner is especially useful for continuum radio astronomy in these bands because it has a large IF bandwidth.  This project was inspired by amateur astronomer Bob Sickels, who suggested using television tuners for radio astronomy in his homebrew classic "Radio Astronomy Handbook". (Available from Radio Astronomy Supplies via the link below.)

Amateur Radio Astronomy Receiver using Television Tuner

The Tuner is controlled via the parallel port of your computer, exactly as described for the FM Wideband Receiver Project.  A good plan is to build and operate the Tuner as a simple FM receiver first, before moving on to this Radio Astronomy project. Instead of using a computer, it is also possible to control the tuner using a PICAXE chip, as described for the PIC Controller Project. The PIC project is simple, inexpensive and avoids tying up a computer.

A directional antenna is required for making the radio telescope observations.  There are several good options available. The Society for Amateur Radio Astronomy (SARA) has generously published detailed plans on the web for building a Quagi Antenna for 408 MHz. Another good option is to design your own Yagi antenna using the free computer software program 'Quick Yagi'.  We have provided links in the Resource Center (below) for both options. Finally, you can build the MTM Scientific Yagi UHF Television Antenna Kit for channel 37, which is a protected  frequency for Radio Astronomy observations.

The Automatic Gain Control (AGC) on the Tuner must be disabled for the radio telescope project.  This is most easily accomplished by connecting a wire to the first pin on the 4 pin connector that connects the VIF unit to the Tuner.  Run the wire to +12 VDC.  Here is a photo of the modification. Note that the sheet metal covers have been removed for the picture.

Automatic Gain Control (AGC) modification of tuner 

An AM Detector is needed to convert the IF output signal of the tuner to a DC signal for amplification.  A simple diode detector is suitable for this frequency range.  A suitable detector circuit is shown here from the "Radio Astronomy Handbook" by Sickels, courtesy of Radio Astronomy Supplies.

AM Detector for Radio Astronomy Telescope by Sickels

A DC Amplifier is used to amplify the small millivolt signal from the AM Detector.  It is possible to build a very nice single supply instrumentation amplifier using a single IC, such as the Burr-Brown INA126.  A single external resistor sets the gain from 5 to 10,000. Here is a link to a circuit diagram and source for the IC amplifer: DC Amplifier Circuit.

A data recorder is used to collect and store the signal from the radio telescope. We describe a simple and inexpensive serial port data logging project here: A/D Data Logger. Another good option is the commercial data acquisition module, complete with software, that is available for about $25 plus shipping from Dataq.  It is their DI-194 "Starter Kit". The DI-194 data acquisition module attaches to your computer.  The WinDaq software  provided with the module creates a real time graphical display of the data which simulates a strip chart recorder. See the Resource Center for a link to Dataq.

Here is a data recording of a transit of Cassiopea A, which is a very powerful radio astronomy source.  This particular trace was taken using the UHF YAGI Beam Antenna from MTM Scientific, Inc built for UHF channel 37.

Cassiopea A Radio Astronomy Source

RESOURCE CENTER:

Here is a list of useful resources for building a radio telescope with the tuner...

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