dmr WFM ? NFM ?

[jfmartin]

I have noticed something strange, through the dsdplus it detects me better signal with WFM and the BCD436hp detects me as NFM .. I let capture:

 

[jfmartin]

I realized that this Motorola DMR RAS system seems to receive better with FM mode and worse with NFM ..

 

[Ubbe]

The 436 uses two different filters for NFM and FM and it might be that the NFM filter have more ripple and phase shift over it's whole bandwidth compared to the FM filter that are used more in the center of its bandwidth and not at the edges. It doesn't matter with analog signals but the more complex and high frequency intensive the datasignal are the more it will suffer from these kind of distorsions. If the circumstances with adjacent channels are favorable that they do not interfere then the wider FM filter probably have less distorsion, if the signal isn't weak and noisy.

/Ubbe

 

[XTS3000]

Like Ubbe said, the 436 has 2 physical 455khz filters, which have very good tolerances. A SDR doesn’t have different bandwidth filters, so it’s done on the software side in conjunction with whatever SDR your using. From your photos, in WFM, your bandwidth is 15.290khz, which is not that far away from a proper NFM filter of 12.5khz.
I see the same thing on my RTL-SDR and signals, they all show up slightly higher in bandwidth vs. watching the same signal on a spectrum analyzer.
Chalk it up to the cheap SDR your using and the fact they don’t have multiple hardware filters like the Uniden 436/536 (and SDS100/200).
No offense to the OP about “cheap SDR”, but you get what you pay for. Heck, even a more expensive HackRF exhibits the same behavior of the cheap RTL.

 

[jfmartin]

Jeje ok thanks