Hrmmm... well, I just lost a decent post, guess I'll let it go.
/me hates computers and wireless connections sometimes...
Basically the gist of that "Mega-post" was that since you're talking about an NXDN system, there is a chance that the particular equipment in use is using offset frequencies because that's what NXDN is capable of supporting. Your actual scanner may not be able to provide you with a
dead-on signal because of how it tunes frequencies and to what accuracy which is incredibly important with NXDN more so than any other digital protocol in my experience.
If you happen to live in an area where an NXDN system (or several depending) is/are using offset transmissions that will mean they have an assigned frequency from the FCC, say 451.2625 MHz, but because they're following the narrowbanding mandates now in place the equipment is capable of transmitting on frequencies slightly above and below the licensed one. In my area, 451.2625 is licensed to Rebel Wireless (FCC license WPMT214) but they don't transmit on that frequency: they transmit on 451.259375 (-3.125 kHz offset) and 451.265625 (+3.125 kHz). See what I mean about the accuracy of the frequency there? It's 6 places past the decimal point and most scanners can't tune things with that level of accuracy properly.
Yes, you can tune close to it, but it won't be
exactly what it needs to be which would mean that the signal you're feeding DSD+ even using the discriminator tap still won't be good enough in terms of clarity and quality for DSD+ to work with it. It's possible, mind you, I'm just saying that old Pro-79 you have can't tune things with enough accuracy for it to be of any use to you in this respect. I've got an older Pro-series scanner here myself, basically useless for most intents and purposes, and even though the display will show 4 places past the decimal point I can't use it for trying to provide a discriminator tap for NXDN content because of the offset systems here in my area and the fact that the offset frequencies are 6-digits precise to get the transmission in the clear.
Hope this makes sense. I can't say for certain if the NXDN content you're trying to tune in your area is or is not using offset frequencies, but if it is, and it's using something that the Pro-79 simply can't tune accurately or precisely enough, you're never going to get a solid decode from it. I don't think that even using dsdtune on the signal will provide enough accuracy of the signal for DSD+ to do its magic, but it can't hurt to try.
If I'm wrong about all this and you get it working, fantastic, but I figured I'd post the info just in case - I know that scanner is somewhat old nowadays and because of the 6-digit accuracy some systems transmit on in terms of frequencies the older stuff literally either can't hear it or it'll almost act like what you're trying to monitor is on a sideband to some degree.
As for the other digital modes like P25, DMR/MOTOTRBO, etc, while they could use offset frequencies for transmissions I've yet to encounter one that did. Seems to be more trouble than it's worth but because of narrowbanding and digital protocols really moving in pretty fast, sooner or later two-slot systems using offset transmissions for two 6.25 kHz wide channels inside the 12.5 kHz spacing will become a lot more common and those older scanners won't be of much use anymore.
Of course you could solve this potential problem with a $10-20 RTL stick, easily.
