I'm trying to use DSD+ fastlane to decode audio from an analog scanner that is coming into the PC through line in. I've had no luck so far. When I use DSD+ with a virtual audio cable coming from SDRUno, I've learned that I have to disable anything that filters the audio or else DSD+ can't decode it. I'm wondering if the analog scanner might have built-in audio filtering geared towards voice that makes it unreadable to DSD+. Anyone have any experience with this?
DSD+ with scanner audio on PC line in
- Thread starter qdude
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Looks like I need to install a discrimator tap then. I found a how-to for my Pro-163 scanner. Thanks. I think I have what I need around here somewhere.
wgbecks
Active Member
Like a417 said, you'd need a modification to break out the discriminator that will probably cost you more than an RTL SDR dongle. Scrap the discriminator tap idea and get an SDR. Besides, you'll be able to trunk track with a single SDR with DSD+ FL. Works fine lasts a longtime.
Arkmood
Member
Yes filtering must be turned off in SDRuno/SDRplay, and yes the 163 discm. tap is an extremely easy mod (b/c TP4) and, yes SDR dongle is a good option...
slicerwizard
Member
With that simple 10k resistor tap, you'll end up with compromised decoding.
10k into line in = terrible low frequency response
10k into mic in = overdriven audio
Arkmood
Member
Could the compromise be defeated by careful adjustments to the line in audio?
10k in series with a 1k pot for a voltage divider network into mic in(tap input in parallel with 1k pot)?
Marsrr
Member
Did you try playing with the sound level of the input? For me it works fine with several scanners, without discriminator tap. Audio level to high or to low gives poor decode, maybe try between level 50 and 70 in the Windows audio settings. (If you did not already try this)
Thanks for the tips. I ordered parts and installed a discriminator tap today. My soldering isn't pretty, but it's a solid connection and I didn't break anything. The tap works. 
Now I can now decode P25 scanner audio with DSD+. This is incredibly useful. However, I'd also like to scan mixed analog and P25 channels. Unfortunately, the tap bypasses squelch. So, with the tap giving constant audio and DSD+ set to output all audio (to hear analog) this means constant noise between calls. I've searched online for a circuit board diagram to see if there is a tap point after the squelch gate but before filtering. No luck yet with such a diagram.
Yes, a new scanner would solve all of this, but I have fun with these projects and squeezing more value out of equipment I already own.
Now I can now decode P25 scanner audio with DSD+. This is incredibly useful. However, I'd also like to scan mixed analog and P25 channels. Unfortunately, the tap bypasses squelch. So, with the tap giving constant audio and DSD+ set to output all audio (to hear analog) this means constant noise between calls. I've searched online for a circuit board diagram to see if there is a tap point after the squelch gate but before filtering. No luck yet with such a diagram.Yes, a new scanner would solve all of this, but I have fun with these projects and squeezing more value out of equipment I already own.
slicerwizard
Member
Sounds like you should be using monitoring mode #1 (Monitor Source Audio if No Sync and Signal Present)
Of course! Thank you. That does the trick. I had gotten so focused on the scanner side of the project that I forgot to adjust DSD+. I'm getting a tiny bit of static breaking through now and then, but this is very good.
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slicerwizard
Member
Yeah, I use it sometimes to scan a bunch of ham channels and they're a mix of analog, DMR, D-Star and Fusion repeaters. Gets the job done.
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