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DSD Plus can't quite get there

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#1
OK, I made a similar post to this which got deleted (I have no idea why, there was nothing wrong with it) .. but I will try this again.

I am very close to getting DSD Plus in combination with SDR Sharp to work to decode P25. I see the signal spikes, the color bars of the signal etc. ... but what I get is choppy audio. I can make out some of the words, but sounds like a person with a bad cell phone connection, where you get a couple words and then it drops out.

I've messed with:
bandwidth (tried around 12.5 or 9.5)
order (usually between 500 and 800)
I have no audio filters or noise blankers on
usually have the sample rate around 1.92 msps (sometimes higher or lower, never above 2.4)
RLT AGC on (usually, doesn't seem to make a difference either way)
RF gain slider on in many different positions
PPM at 0 (usually)
using the VB cable properly as far as I can tell
the antenna I'm using is the bigger telescopic ones that came with RTL-SDR dongle (tried smallers ones too)

I feel like I'm just a setting or two away, but I can't seem to get it.
Anyone care to shed some light on this ... or maybe your settings if you are getting this to decode properly?

One final note, I noticed I have that FMPA file in my DSD Plus folder. I'm not using that at all, I couldn't get it to open up anyway. I'm just using SDR Sharp and DSD Plus.

Thanks for any guidance.
 

rbrtklamp2

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#2
Well let's start with the basics what kind of SDR are you using? Also have you set VB Audio Cable as the default sound input or recording input device? And last have you tried playing with volume level in your audio settings for VB Cable it has to be just right to get a proper decode of the signal.

Sent from my SM-N910V using Tapatalk
 
Joined
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Messages
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Location
Rochester, NY
#4
Well let's start with the basics what kind of SDR are you using? Also have you set VB Audio Cable as the default sound input or recording input device? And last have you tried playing with volume level in your audio settings for VB Cable it has to be just right to get a proper decode of the signal.

Sent from my SM-N910V using Tapatalk
I'm using a RTL-SDR dongle with SDR Sharp software.
VB Cable is the default recording device.
Under the "Audio" tab in SDR sharp, VB Audio Cable is set as the output (labeled as Windows Direct Sound Cable Input (VB-Audio Virtual Cable). The input (which is greyed out and I don't have access to) is MME Microsoft Sound Mapper-Output. (Which seems odd, the input has a selection labeled output and the output has a selection labeled input). Confusing, but I was following directions on it. (see pic)

Under DSD interface, I've unchecked enable aux audio output. (I sometimes check this and it doesn't seem to make a difference) The audio device selected is Windows Direct Sound Cable Input (VB-Audio Virtual Cable). (see pic)

I also tried adjusting levels in sound panel for VB cable, and it didn't seem to make much difference.
 

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