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Ask Dr. SETI ®

Chapter 6: Technology

Antennas in Limited Space

Dear Dr. SETI:
I am finding it to be very important to myself that I find some means of setting up a listening station in a limited space. I can't believe that this is impossible anymore than I can believe that we are alone in the universe. Therefore, until my resources are expanded beyond what they are at the moment, I will be researching how to set up a SETI station in a small space and still get the sensivity and resolution needed. Do you have any suggestions on how this might be done, or where I should look for help on this issue?

Dave, CT

The Doctor Responds:
Antennas are always a problem, Dave, for those with limited real estate (and since CT is a small state, I assume that is your situation). I assume you just can't swing a satellite TV dish. A couple of possible alternatives present themselves:

  1. Start off small, and work your way up when you're able. You could, for example, put up one loop yagi (that would be maybe 12 dB less gain than a TVRO dish, which means you'd only "see" one-quarter the distance, all else being equal). Later you can consider arraying two, four, or eight of them, space permitting, to increase your range.

  2. How about a small dish at a higher frequency? Since an antenna's gain is proportional to its aperture measured in wavelengths, every time you double frequency you can halve the dish size. So figure out the largest dish you can swing, and scale frequency accordingly. For example, if a 5 meter dish at 1.4 GHz is ideal, then a 1 meter dish at 7 GHz would perform similarly. (This assumes that you can get receiving equipment for the higher frequency, and that ET happens to be transmitting there!)

At the moment we consider all microwave frequencies to be fair game for interstellar communications. The ready availability of receive converter kits for the 13 cm, 5 cm, 3 cm, and even the 1.25 cm ham bands should significantly increase your options. And even though The SETI League is concentrating its engineering efforts on the 21 cm hydrogen line at the moment, we'd like nothing better than for one of our members to develop an "all-band" microwave scanner! Feel like doing some pioneering work, Dave?

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