Video of indoor, ultra-cheap cubesat operations
I had a chance to do some more listening in on CO-55 using my FT-817 radio and a 1/4 wave ground-plane made of wire and a BNC. Given the number of all-band, all-mode radios that are available now, I think a simple experiment like this could be great fun to many hams, especially those who might fear that satellite operations of any sort are prohibitively expensive. In hopes of illustrating to them and others, I made a short video of the actual reception, to be viewed here: http://video.google.com/videoplay?docid=1251407580465862002 The audio does not do justice to the CW reception: it seems to roll off in the low frequencies so I was able to copy the telemetry much better than it might seem. I was tempted to process the audio, but I figured people know that these sorts of video recordings have crummy audio. I suppose the video needs some contextualizing for non-Amsat folks, but it's a start.
This morning I used the same setup to listen to a 2 deg. max elevation pass of LO-19. Its signal is stronger, of course, but it probably would be less well-suited to demonstration because it sends telemetry periodically, not continuously. It is easy to lose the signal in the doppler as the telemetry goes silent. However, with a practiced hand, familiar with the period of the LO-19 telemetry it is quite possible to record 559-ish copy from this bird without a preamp and with a directly-attached 1/4 wave vertical.
I wonder if one could design a circularly-polarized antenna for 435 MHz that directly attached to the BNC and could be supported by an FT-817...
On Jan 25, 2008 9:28 PM, Bruce Robertson [email protected] wrote:
I had a chance to do some more listening in on CO-55 using my FT-817 radio and a 1/4 wave ground-plane made of wire and a BNC. Given the number of all-band, all-mode radios that are available now, I think a simple experiment like this could be great fun to many hams, especially those who might fear that satellite operations of any sort are prohibitively expensive. In hopes of illustrating to them and others, I made a short video of the actual reception, to be viewed here: http://video.google.com/videoplay?docid=1251407580465862002
Hi Bruce,
I think the eggbeater style antenna might do the trick. I don't know about the BNC on the 817 or how you want the 817 to be oriented, but it might support the weight of a extra lightweight eggbeater. I'm building one from solid copper wire of 6mm² (between AWG 9 and 10), but thats what I have in the junkbox, smaller wire should be no problem.
The only "difficulty" is to obtain the RG-62 93Ohm Coaxial cable for phasing, but a few post back some was offered for just postage costs.
My eggbeater is still in trial and error construction phase (which materials, how to build one?) but it already looks quite nice. There are a couple of descriptions on the net.
Good luck working the birds from the 817!
73
Wouter PA3WEG
On Jan 26, 2008 1:59 PM, Bruce Robertson [email protected] wrote:
This morning I used the same setup to listen to a 2 deg. max elevation pass of LO-19. Its signal is stronger, of course, but it probably would be less well-suited to demonstration because it sends telemetry periodically, not continuously. It is easy to lose the signal in the doppler as the telemetry goes silent. However, with a practiced hand, familiar with the period of the LO-19 telemetry it is quite possible to record 559-ish copy from this bird without a preamp and with a directly-attached 1/4 wave vertical.
I wonder if one could design a circularly-polarized antenna for 435 MHz that directly attached to the BNC and could be supported by an FT-817...
On Jan 25, 2008 9:28 PM, Bruce Robertson [email protected] wrote:
I had a chance to do some more listening in on CO-55 using my FT-817 radio and a 1/4 wave ground-plane made of wire and a BNC. Given the number of all-band, all-mode radios that are available now, I think a simple experiment like this could be great fun to many hams, especially those who might fear that satellite operations of any sort are prohibitively expensive. In hopes of illustrating to them and others, I made a short video of the actual reception, to be viewed here: http://video.google.com/videoplay?docid=1251407580465862002
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
----- Original Message ----- From: "wouter weggelaar" [email protected] The only "difficulty" is to obtain the RG-62 93Ohm Coaxial cable for phasing, but a few post back some was offered for just postage costs.
If any AMSAT member needs some RG-62, just send me an SASE to my callbook address and tell me how many feet you need.
73, Drew KO4MA
On Jan 26, 2008, at 4:59 AM, Bruce Robertson wrote:
This morning I used the same setup to listen to a 2 deg. max elevation pass of LO-19. Its signal is stronger, of course, but it probably would be less well-suited to demonstration because it sends telemetry periodically, not continuously. It is easy to lose the signal in the doppler as the telemetry goes silent. However, with a practiced hand, familiar with the period of the LO-19 telemetry it is quite possible to record 559-ish copy from this bird without a preamp and with a directly-attached 1/4 wave vertical.
I wonder if one could design a circularly-polarized antenna for 435 MHz that directly attached to the BNC and could be supported by an FT-817...
Filed under the department of coincidences, I tried decoding the LO-19 telemetry a couple of days ago. The thing is: I don't have anything except my trusty TH-D7A (FM only dual band HT). I was really just curious if I could hear it. The answer is yes, and in fact, it wasn't hard to decode the Morse that it sent (crude as my morse skills are) by simply looking for the dots and dashes as changes in the background noise. If my decode of the telemetry was right, it was putting out 1027 mw of TX power, which is art of what made it really easy.
Recordings and decodes here:
Continuing this series of observations, using very simple antennas indoors with my FT-817:
I worked on a eastward 5 deg. max elevation pass of XI-V, or CO-58, this evening. This cubesat has a nominal output of 80mW. Its periodic transmission makes it less ideal than CO-55 for this sort of experimentation, but the break between transmissions is not as long as LO-19's: in my experience with this low pass it never doppler-shifted out of the 500 Hz filter while silent. I had to have only the exterior wall between me and the bird for it to be reliably heard.
If I've done the math right, this is a free-space path loss of about 153 dB on a, roughly, +20 dBm signal, meaning that the receiver can hear down to at least -133 dBm at 500 Hz bandwidth (since we haven't factored in the losses due to the indoor reception).
A dipole mounted directly on a BNC copied VO-52's 2m downlink quite well for a couple of minutes, both from the second storey of our home and from the first. By the time I found my video camera, there was apparently no activity. Possibly the dipole's pattern got in the way of reception.
I would be very interested to hear if anyone else has had success with similar minimal equipment. I hope to take this setup to a more urban environment and see if it will still work, say, outdoors.
73, Bruce VE9QRP
participants (4)
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Andrew Glasbrenner -
Bruce Robertson -
Mark Vandewettering -
wouter weggelaar