Issue with decoding POCSAG

AX.25 packet, ChirpChat (LoRa), FT8, 802.15.4, RTTY, PSK31, Pager, and APRS
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Joined: Tue Oct 31, 2023 5:34 pm

Issue with decoding POCSAG

Post by mknlsn »


So for some reason I'm not able to decode any POCSAG pager messages. Here's a screenshot of my current settings: Image
Posts: 327
Joined: Thu Jan 19, 2023 2:30 pm
Location: London

Re: Issue with decoding POCSAG

Post by srcejon »

A couple of things:

- Firstly, your pager channel crosses DC (The device center frequency) and you have DC offset removal enabled (in the RTL SDR Device settings DC is highlighted), so this will filter part of the signal. Preferably, don't have the channel crossing DC. E.g. set device center frequency to 929,000kHz and then put your Pager Demod delta f to 15kHz.

- You shouldn't need your BW wider than the default of 20k.

- Secondly, I'm not convinced that quite looks like a POCSAG signal. In the UK at least, the two peaks from FSK are quite a bit sharper and the tones during preamble are more visible. But perhaps there's some filtering in the US. Here's a picture what I see:
POCSAG.png (1.65 MiB) Viewed 1129 times
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