Overview

Believe it or not, it is possible to do Radio Astronomy at home. Especially if you consider Radio Astronomy to include all frequencies from "DC-to-Daylight". But even if your idea of Radio Astronomy is searching for deep space objects at microwave frequencies, you can put together a complete radio telescope for a few grand, assuming you can scavenge a Big Ugly Dish (BUD) from a neighbor who once used it to get Satellite TV.

You can also do interesting work at lower frequencies, probing changes in the ionosphere which are affected by both solar activityand also possibly by Gamma Ray Bursts from deep space

 VHF and Above

The system that I'm building (Things like this are never really complete...) is based on a basic receiver with a 135 to 150 MHz input frequency range. This is built around a military surplus ARR-52 VHF receiver originally intended to receive signals from Sonobuoys. Looking back, this was a masochistic thing to do, and I can't recommend that anyone else do it. I've added some Radio Astronomy specific features around it and packaged it in a 3U rack mount enclosure. Here's a link to a few pictures and a block diagram of the Radio Astronomy Receiver.

In front of this receiver will be a variety of antennas and down converters for various Radio Astronomy bands. Currently, I have a copy of the SARA 408 MHz Quagi antenna and a home-brewed down-converter. This is still being debugged.

One thing I found out was that the LNA needed to be temperature controlled to avoid losing the desired signal in the noise change caused by temperature swings at the LNA. Here in Santa Rosa, our temperature can change from the 50's in the morning to the 90's in the afternoon. To optimize the performance of the DEMI LNA that I'm using, I decided to use a Thermo-Electric Cooler (TEC) module and control the LNA temperature to 0 deg. C. Go here for details.

  Ionospheric monitoring

I am monitoring VLF signals to record disturbances in the Ionosphere. This is done by measuring the received signal strength of various VLF transmitters throughout the day. The one I use most is NLK in Jim Creek, Washington on 24.8 KHz. I use an HP 3586C Selective Level Meter, fed by a "Monopole" antenna - basically a piece of 3/4" Copper water pipe mounted vertically. This is connected to the input of a high impedance buffer amplifier. The pipe acts like a capacitive probe, picking up the electric field.

Every day that the transmitter is active, I get a distinctive pattern, with a dip in the signal strength at dusk and at dawn. This is the main reason that I choose to monitor a station almost due north of me. As the sunrise or sunset terminator sweeps across the earth, the effect on the radio path will be most dramatic if the path is North/South, since the terminator goes through the whole path very quickly. If the transmitter were East of me, the terminator could take hours to traverse the path.

For more details, see my Ionospheric Monitoring Pages

  Data Collection

To monitor the results, I am taking advantage of spare channels in my seismic monitoring system to act like a chart recorder. This works very well. I have the seismic system set to sample the inputs 100 times per second, and then record the data to the hard disk. The software that came with the board allows me to view the data in real time or review it from the disk. Go to my Seismic Page for more information about the board and the software.

An important part of any monitoring program like this is to have good time references for the data collected. I have a very nice High Precision Time and Frequency Reference System for my lab.

Here are some great links to Amateur Radio Astronomy information:

Last Revised: 30-December-2005