[Hackrf-dev] Narrowband fm - what is the secret?

[Cinaed Simson]

Hi - neither APRS or AFSK are FM modulated.

AFSK is digital and uses 2 frequencies - FM is analog and uses a wide
range of frequencies.

APRS is packet based and you need to decode it - which is what your
handset is doing.

See if SDR has a APRS decoder plugin.

Note, gqrx has a APRS decoder.

-- Cinaed


On 09/14/2016 09:03 AM, Gavin Jacobs wrote:
> Yesterday (thanks to help here on this mail list) I got my hackrf One
> working as an FM receiver. I have SDR# v1.0.0.1483 running on Windows
> 10. So, today I want to move on to narrowband fm. I picked APRS channel
> because there is steady traffic. I tuned SDR# to 144.39 MHz, NFM,
> bandwidth 8k, LNA gain 32, VGA gain 24, amp off (also tried on), squelch
> off, antenna adjusted to 52 cm.
> 
> If I key my handheld, I see a big spike on the frequency; and if I zoom
> in, it appears centered on 144.39.  Meanwhile, on my handheld, I can
> hear the AFSK tones, so I know there are signals coming in, but the
> hackrf/SDR# doesn't change (neither frequency nor audio).
> 
> My first guess is that I have missed some RF setting, but I've been
> through the menus and can't find anything.
> 
> Once again - any advice is welcome.
> 
> 
> Jake
> 
> 
> 
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