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 "Radio Astronomy Handbook". (Available from Radio Astronomy Supplies via the link below.) Please Note: You can get a quick start on this project by using our CATV Tuner Motherboard, available on our main CATV Tuner Page.

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. Another option for controlling the tuner is using a PICAXE controller, as described on our PIC Project Page.

A directional antenna is required for making 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 those options. Also, MTM Scientific is planning to offer an antenna kit specifically for UHF channel 37 soon. Until then, here is a link to simple plans for building a homebrew version of the same antenna we will be offering: Antenna Plans. This antenna works very well for drift scan observations in the 608-614 MHz range.

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 INA122.  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. One good option is an inexpensive data acquisition module, complete with software, that is available for about $25 from Dataq.  It is their DI-194 "Starter Kit". The DI-194 data acquisition module attaches to the serial port of a 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) Another option for recording the data is to build our Low Cost A/D Converter using a Picaxe chip. 

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 a YAGI Beam Antenna 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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