P25 & sdr

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ausscan

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Hi all,
Our county fire department is moving towards a P25 single frequency dispatch system and I was wondering if any one has successfully setup a USB SDR using SDR Sharp and piped it into a P25 decoder with success on Windows 7? How did you achieve this outcome and what obstacles did you face along the way?

Cheers
 

n9mxq

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I run SDR# and DSD for Windows and the only problem I've found is if I forget to turn off my BOINC (SETI) software.. It will mess with decoding by not letting the CPU do it's thing...

Otherwise I've had no problems at all with it decoding P25
 

mtindor

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Hi all,
Our county fire department is moving towards a P25 single frequency dispatch system and I was wondering if any one has successfully setup a USB SDR using SDR Sharp and piped it into a P25 decoder with success on Windows 7? How did you achieve this outcome and what obstacles did you face along the way?

Cheers

I've used a Funcube Dongle Pro (the original, not the +) on Windows 7 64-bit.

Dongle --> SDRSharp --> VAC (Virtual Audio cable) --> [DSD | DMRDECODE | Unitrunker]

So basically, in SDR Sharp I set the input to my Funcube Dongle and set the output to "Virtual Audio Cable Line 1". In my Recording Devices I set Virtual Audio Cable Line 1 as the Default Recording Device. In my Playback Devices I set my speakers as my Default Playback Device.

With the Default Recording and Playback Devices set properly, then when DSD is ran it knows to get its input from the VAC output and it knows to send the decoded audio to my speakers.

DSD [in Windows] requires that the Default Recording and Playback devices be set to the devices that DSD will be getting its raw audio from and where it will be sending the decoded audio to.

I don't know about other SDR dongles, but for the Funcube, you want to set the audio level on the Funcube Dongle Recording Device to 1 or 2, no greater. Otherwise, you'll end up with a lower SNR.

I don't just listen to P25, and in fact most of the time I don't since I have a digital scanner. But from time to time [like tonight, with some enhanced propagation] I'm listening to some conventional P25 on 450 Mhz with the dongle because I already had it connected.

Mike
 

mtindor

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As Gene alluded to, CPU is an issue. You should have a beefy multicore machine to run the SDR software, VAC, and DSD [mainly for DSD's sake]. My old Intel T5750 (Core Duo) laptop didn't cut the mustard. My Intel I7 laptop has no problem.

Some SDR is much less resource intensive than others. If CPU power is an issue for you, you'll probably want to play with different SDR software and find whatever uses least resources.

mike
 

n9mxq

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And I should also mention that I'm running the el cheapo DVB-T dongle that rose to eBay stardom.. With my copy of Win7 Home Premium (64bit) I found out AFTER I bought VAC that I could use the built in Stereo Mix that came with Windows.
 

ausscan

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So basically I need a beefy CPU and VAC? How beefy is beefy? I mean, I can't see my 1.86ghz dual core Intel being able to cut the mustard?
 

AD8NT

Sarah Rose (Formerly KR0SIV)
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I couldn't say ausscan,
I run a 3.2GHz Quad Core AMD CPU and it does fine for me
Windows 7 X64
 

n9mxq

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If it's not a trunked system, yes I consider it solid. I can get 100% decode on P25 up here. If it's a trunked system, then you'll need 2 sdr dongles and a bit of fiddling with SDR# to get it to work. (I've never used mine for trunking..)
 

AD8NT

Sarah Rose (Formerly KR0SIV)
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SDR# can do trunking... although I've not found DSD to be all that great
 

davemcfarland

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trunked p25

We are trunked p25 here and I have the typical scanners, 396xt and others, including the first SDR pr100 icom.

I would love to have a devoted pc to place somewhere that can be streamed and if I lost access or something happened I wouldnt be out of my 450 dollar scanner..
 

n9mxq

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I've heard good things about SDR# and trunking with 2 dongles, but as I stated I've never done it.

I think it would be fine for what you propose once you get it working.
 
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