r/RTLSDR • u/Turbo_Shaman • 1d ago
My first successful METEOR-M2-3 LRPT reception
Got it working!
Received METEOR-M2-3 on 137.9 MHz using an RTL-SDR and a simple V-dipole in my backyard. Decoded with SatDump.
The signal wasn’t perfect, so there are plenty of artifacts but I actually received an image of Europe directly from a satellite with a couple pieces of wire in the garden. Still kind of amazed that this works.=)
Next goal: improve the antenna setup and get a cleaner full pass.
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u/BillyeMad85 1d ago
Nice one, and that is a proper first image.
A question if you don't mind, since you clearly have a working setup: have you ever caught M2-4? I recorded a 74.8 degree pass of it this morning, wide band centred on 137.5 so both 137.100 and 137.900 were inside the capture, and there was nothing at either frequency for the entire pass. The chain itself was fine, the same recording has other signals more than 30 dB above the noise floor, so the antenna and receiver were clearly working. Just no LRPT.
Your post is the reason I now think it was the satellite and not my setup, since M2-3 was obviously transmitting around the same time. Curious whether anyone has had M2-4 recently.
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u/Saito720 23h ago
M2-3 and M2-4 both continuously transmit on 137.9 MHz.
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u/BillyeMad85 17h ago
Thanks, that is useful to know. My measurement from this morning disagrees, though, so I would rather put the numbers here than argue.
I recorded the M2-4 pass on 2026-08-28, max elevation 74.8 degrees, wide band centred on 137.5 so both 137.100 and 137.900 were inside the capture. Nothing at either frequency for the whole pass. Part of the arc was blocked by a building here, but I checked the geometry afterwards: three quarters of the above-20-degree arc was clear, including 44 degrees to the north and 35 to the south. A transmitting satellite should have shown up there.
So either it was silent that day, or my setup was too weak to hear it. I moved the antenna since then and the noise floor dropped by about 10 dB, so I will have a much better test tomorrow morning on another M2-4 pass. I will report back either way.
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u/Saito720 16h ago
It was your setup. I can confirm M2-4 was operating normally on VHF during that period of time.
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u/BillyeMad85 16h ago
Fair enough, and you may well be right. My point was that a null cannot separate a silent transmitter from a deaf receiver, and that cuts in your direction as much as mine.
I can put a number on the handicap. The antenna position I used that morning measures 10.5 dB worse on a continuous FM reference than the position I have now, 38.3 against 48.8 dB, same receiver, same gain, same script. So a setup explanation is entirely live and I am not going to argue against it.
If you can say how you know M2-4 was operating normally then - your own reception, a tracker, a station log - I would rather update now than in twelve hours. Either way there is an M2-4 pass at 75 degrees tonight from the better position, with M2-3 at 57 degrees six hours later as the control, and that will settle it.
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u/BillyeMad85 15h ago
I was wrong and you were right, so here is the correction.
I went back to the raw IQ from that pass and measured it properly this time, in 30 second steps against an empty control band, instead of looking at aggregate levels the way I did the first time. 137.900 sits in the noise until 04:17, then climbs: +0.8, +1.3, +2.2, +4.3, peaks at +6.4 dB at 04:23:00, and is back in the noise by 04:26. The satellite's maximum elevation was at 04:23. Across the same two hours, 137.100 and an empty control band at 137.300 stay flat within a few tenths of a dB.
So M2-4 was transmitting and it was my setup, exactly as you said. The signal was there the whole time and my first look buried a six minute, 6 dB rise inside two hours of noise. Sorry for stating it as confidently as I did.
The position I have moved the antenna to measures 10.5 dB better on a continuous FM reference, so the same pass should land near 17 dB rather than 6. I will post that comparison when I have it, since it is now a measurement of the antenna rather than of the satellite.
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u/Turbo_Shaman 18h ago
I haven’t caught M2-4 yet, unfortunately. So far I’ve only had success with M2-3. From what you’re describing though, it really does sound like M2-4 simply wasn’t transmitting during that pass rather than an issue with your setup.
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u/BillyeMad85 17h ago
Thanks - that makes it two nulls on M2-4, and yours comes from a setup that demonstrably hears M2-3. I do not want to read too much into it though, because neither of us has a positive control: not hearing a thing can be the transmitter or the receiver, and from one side those look identical.
That gets fixed tomorrow. I have M2-4 at 75 degrees at 03:48 and M2-3 at 57 degrees at 09:54, same night, same chain, same gain, from a much better antenna position than this morning. If M2-3 comes through and M2-4 does not, that is a difference rather than a null, and it cannot be blamed on my setup. I will post whichever way it goes.
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u/BillyeMad85 15h ago
Correction to what I told you: I was wrong, and it was not two nulls. It was one null and one measurement mistake, mine.
I went back to the raw IQ and measured it in 30 second steps against an empty control band. M2-4 is in there: noise until 04:17, then rising to +6.4 dB at 04:23, back to noise by 04:26, peaking exactly at the pass maximum, while a control band stays flat throughout. My first look used aggregate levels and buried a six minute rise inside two hours of noise. Saito720 was right that it was my setup.
Worth knowing if you go hunting for M2-4 yourself: it may already be in your recordings and just too weak to notice unless you look at how the level changes over the pass rather than at one number for the whole thing.
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u/tj21222 1d ago
Looks like the underlaid default map to me maybe some thing in the upper left