This is Major Tom to ground control

My friend Greg and I spent several nights this past week attempting to listen to amateur radio signals from the International Space Station (he’s been using Gpredict to find time windows of orbits close to us). Not only is one of the crew members on the station a ham, but they also have a fully functioning repeater on the station as well. The uplink frequency is 437.800 MHz and the downlink frequency is 145.800 MHz. I had my squelch turned to minimum and my volume set high, but I never heard anything but white noise. Oh sure, I fleetingly thought that I had a variety of contacts, but that was just my brain playing tricks on me. It’s a well-known psychological quirk that people can fool themselves into hearing meaningful noises in pure static, or seeing patterns in random shapes.

I spent twenty minutes on each of several different nights listening to white noise, straining with all my mental might to hear something amidst the cacophony. But we never heard anything. None of the orbits brought the ISS closer than 800 miles. It was simply too far for our receiving equipment. We both have 44-inch magnetic mount dual-band whip antennae, the kind that can be affixed to the top of a vehicle. They’re good for ground-based mobile operations, but not for trying to receive signals from space! For that, you really want a cross-polarized Yagi antenna on an altitude-azimuth mount (imagine how large ground-based telescopes are pointed and you’ve got it). And that represented a far larger investment in the hobby than either of us has made so far. Are receiving transmissions from space limited only to the upper echelons of the hobby? Is attempting it with entry-level equipment as foolish as someone with a cheap telescope from Wal-Mart searching for a new planet? I would soon find out.

After another annoyingly silent ISS pass last night, gpredict showed that the biological research satellite GeneSat-1 (see picture above) was passing almost directly overhead in another twenty minutes. It also happens to be equipped with a beacon operating in the 70cm amateur radio band. I was skeptical, and it was getting late, but I couldn’t miss the opportunity. This would be four times closer than any pass of the ISS so far (and thus sixteen times the signal strength, thank you inverse-square law), so I was hopeful. The frequency of GeneSat-1’s beacon is 437.067 MHz. I can only tune my radio in 5 KHz increments, but the Doppler shift of the orbit spreads the signal out enough that it would be heard on the frequency I tuned my radio to, 437.065 MHz, if indeed the signal was strong enough to be heard at all.

So again I turn the squelch all the way down and the volume up to almost painful levels (if you’re a fan of overblown metaphors, imagine a fighter pilot setting his afterburners to maximum, his plane roaring and rumbling around him). I listened intently as the minutes slowly ticked away. GeneSat-1 crested the horizon; nothing. It began rising higher and higher in the sky; still nothing, though my mind was now alerting on fake signals at an alarming rate, only for each to be rejected after a moment’s consideration.

GeneSat-1 reached its maximum elevation in the sky. I thought I heard something. It seemed different than the other fake signals thus far. I couldn’t make out anything other than a just-barely-there rhythmic pulse of not-quite-random noise with a period of around five seconds. And then I began hearing quieting of the white noise on a five second interval. I was definitely getting enough signal to at least suppress the noise, although the content of the signal itself wasn’t quite strong enough to register. My lingering doubts faded away and I knew that I was really hearing something, something from space.

Then in a triumphant outburst, I plainly heard an AFSK1200 transmission during one of the quieting periods (if you’re old enough to have used a dial-up modem, it sounds exactly like that; if not, imagine a really spastic, hyper, angry bumblebee). It repeated every five seconds, growing louder and louder, each transmission less than a second long yet containing the satellite’s identifier callsign along with some basic telemetry. I didn’t have my radio hooked up to my computer to decode the transmission, but I didn’t care. I was hearing a transmission from space, a radio signal emitted from a tiny 10 pound satellite whizzing over my head right at that very moment at thousands of miles per hour!

The transmissions disappeared just as quickly as they had appeared. All in all, I had heard maybe ten beacon transmissions. The satellite was now rapidly moving down from its peak in the sky (from my perspective). The pervading random static returned once more, but my mind was no longer making up signals amongst the white noise. Having heard a 6-inch long satellite in orbit 200 miles above me using nothing more than a car-mountable whip antenna, it had no reason to make anything up now. The experience had been unreal enough already. I listened to the no-longer-infuriating white noise for another couple of minutes, then went to bed.

9 Responses to “This is Major Tom to ground control”

  1. Jens 'Spacejens' Rydholm Says:

    Congratulations! Having tried amateur radio (in the Scout movement, during the annual JOTA) about 15 years ago (when I was half my current age), I am jealous. We talked to Scouts in Germany and the U.K., which was still nice though.

  2. Cyde Weys Says:

    Talking across the Atlantic is actually a good bit harder than hearing satellites. I only needed $300 in equipment to hear the satellite, but to make contact across the Atlantic, you’ll need a radio that handles longer wavelengths (which is more expensive) and a serious antenna (longer wavelengths need larger antennae). A little whip won’t do. I hope to get an HF rig and antenna eventually, but for now, I’ll be content listening to satellites with my VHF/UHF setup.

    Also, if I managed to hear a six inch long satellite using my setup, I should easily be able to hear the much, much larger International Space Station. I just need to wait for a closer orbit.

  3. Kelly Martin Says:

    The size of the station doesn’t determine how audible its signal is. I can’t find info right now on the power levels being emitted by Genesat and the ISS, but there’s no particular reason to believe that the ISS station is running at higher power than Genesat just because it’s larger.

    You can do transatlantic with VHF/UHF, too, via moonbounce; you just need an amplifier and a directional antenna (a basic Yagi should do).

    That said, you really should get your HF privs, an HF rig, and a 20m end-fed dipole (such as one of these). You won’t get the world’s greatest performance with one of these, but it’ll be more than good enough to do at least some DXing. 10m propagation isn’t going to pick up for at least another couple of years, so I’d bend your efforts toward 20m. A 20m end-fed dipole is only 33 feet long. If your apartment doesn’t give you room for that, get a generator and go play in the field. :)

  4. Jens 'Spacejens' Rydholm Says:

    Well, since I live in Sweden, I was not talking across the Atlantic (unless you count the North Sea between me and the U.K.). :-)

    The antennas we used were a hard wire model (kind of like an old television antenna) mounted on top of the chimney, and a soft wire model strung from the house to and around a tree (kind of like holiday lights).

  5. Cyde Weys Says:

    Kelly’s right, the size of the station doesn’t determine how receivable the signal is, only the output wattage being used. But a bona fide spacestation has much more power available to it than a 6″ satellite. The ISS could easily muster up 1,000 watts for a radio transmission (you see how huge their solar panels are?!); the microsat will be lucky to get a few watts.

    “You just need an amplifier” makes it sound a bit simpler than it really is. Greg and I were pricing out amplifiers for high-wattage HF work a few days ago and the cheapest you’ll find at decent output levels is over $1,000.

    For that price, you can get a pretty nice HF radio and an end-fed antenna and even make contact with stations that aren’t on the same side of the Earth as the Moon.

  6. drinian Says:

    I can remember picking up weather satellite transmissions about six or seven years ago, using an old Uniden Bearcat police-band scanner. I could hear the Sputnik-like repeating “beep” as it moved overhead, and then faded out over the horizon.

    With SSB, I understand you can pick up the data signal and load the real-time images on to your computer. Just being able to pick up anything with that old scanner was pretty amazing, though. I’m actually surprised that it’s that much harder to pick up on the ISS, given how much better your equipment is than mine.

  7. Greg Maxwell Says:

    Well… ISS has been “hard” to pick up only because we haven’t really been trying. Every couple evenings after I finish all the other things I’ve been working on I fire up gpredict and see whats about to fly overhead. If there is something coming I tune in and listen. I also ping Ben and let him know. I’ve heard a couple of things, but ISS has never made a *close* pass while I was listening.

    If Ben really wants to hear ISS he could try tuning in around 03/26 08:11 UTC, 03/27 09:40 UTC, 03/28 07:23, or 03/28 23:48 UTC. All of which will be nice high elevation passes from his location and which will bring ISS within 450mi. (or he could install a prediction program like gpredict himself and not depend on me feeling like looking it up)

    Regarding the commentary on the prices of HF rigs .. it doesn’t have to be all that expensive. What is expensive is buying new HF rigs. I think the easy availability of working old gear has eroded the market for commercial ‘low end’ HF gear as a result only fancy ultra-sensitive … and somewhat expensive rigs are available new. The least expensive HF rigs available new are specialist boxes things which are lower power, or CW only, etc.. The new fancy rigs are nice and have sensitivity and selectivity that will knock the socks off decades old gear, but a lot of old stuff will work quite well for the basic purpose of communicating over long distances. On the used market you have many options.

  8. William (green) Says:

    I think the easy availability of working old gear has eroded the market for commercial ‘low end’ HF gear as a result only fancy ultra-sensitive

    So… how would one go about obtaining some of this easily-available working old gear? At this point, it’s just curiosity, but I know someone in the States who’s looking to get some basic ham gear.

  9. William (green) Says:

    In all fairness, the first post didn’t show up for a day, so I figured it hadn’t submitted. I’m not quite as impatient as you would think from looking at those two.