HFU HF Underground
Loggings => VHF/UHF Logs, including satellites and radiosondes => Topic started by: raypfaff on April 24, 2020, 1223 UTC
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Because I'm at home and bored I started trying to pick up radiosonde transmissions out of the Sterling Va office. I live in Chantilly Va, just a bit south of Dulles airport and I thought that it would be pretty easy to pick up at least the initial ascent. I've been monitoring between about 400-406 mhz at both 1100-1230 and 2300-0030 UTC. I know what the waveform should look like, but I've seen nothing so far, other than some digital transmissions at 400 and 403.2 Mhz which are constantly on. Looking back at the posts on this site, it looks like 401 mhz is a good place to camp, but I've still seen nothing. Am I perhaps looking at the wrong time or are the flights suspended or something? I'm using an RTL-SDR and a Nooelec Ratlsnake antenna; I realize that's not the best choice for an antenna but I feel because of the close proximity, I should be able to pick up something.
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As far as I know they are still on the air. I can try to check tonight or tomorrow for sure. From your location I would expect even an RTL dongle could pick them up, although if you only have a small inside antenna that could be the problem.
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Yeah, I am using a small indoor antenna but I'm able to pick up ADS-B with it out to the Blue Ridge. I realize that's kind of apples and oranges given the different frequencies, but I'm just surprised that I've not been able to see a signal at all.
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I am picking up this morning's launch right now, 1308 UTC (9:08 AM) on 401.010 MHz +/- thermal drift as the radiosonde rises through the atmosphere.
I use a discone antenna about 50 ft up in a tree, and can get over 100 km range.
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Okay, I tried at 1200-1230 UTC. Maybe I'm not waiting long enough for the balloon to get altitude. I'll try again.
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Got it! I have 3 computers with SDR. One Windows desktop that I use to decode ADS-B, one Windows laptop that I have pretty much dedicated to a Funcube (which will not pick up the 400 Mhz range), and one Linux laptop that monitors my power and I occasionally use to catch GOES. Recently I've found that the Desktop generates a ton of RF and that seems to be the problem with picking up the Dulles sonde. It looked pretty quiet at 400 mhz, but I think there's enough noise to wipe out the signal. The Linux box picks up the signal perfectly. Right now I have to save off a .wav file, upload it to one of the Windows boxes and convert it from 32 bit stereo to 16 bit mono, but I was able to decode the signal. I'm using gqrx; it will serve up the audio via udp, but I haven't figured out how to capture that audio on the windows boxes.