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  #1 (permalink)  
Old 11-26-2013, 8:34 AM
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Default BC246T Discriminator

I have installed a discriminator tap on my BC246T.
I am trying to use DSD to decode the digital RCMP trucking TGIDs here in manitoba.
Most are still unencrypted (except the feds) so encryption isnt the issue.

The MTS fleetnet is a MOTO II trunking system and the RCMP talkgroups operate P25 AFAIK.

I have DSD running, and have tried adjusting the volume, I have tried 3 different PCs, all with the same
results. Its like DSD isnt syncing with the digital signal. I might get a few seconds of clear intelligable
speech, but most of the time its a garbled mess.

I have tried running the discriminator directly to the sound card, have tried decoupling caps and padding
resistors, nothing makes a difference.

Anyone have luck using this scanners discriminator to decode p25 via DSD?

What am I missing?
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Old 11-26-2013, 9:21 AM
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How much horsepower does your computer have? My Intel i3 2.4 GHZ seems to be just barely up to the task.

Fire up Task Manager and see your CPU load. If you are loading it much over 50% I think you will have problems.
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Old 11-26-2013, 10:01 AM
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Quad core intel i5, 2.7Ghz, 8GB ram win7. I got the power, I think anyway.
It does no better than the old IBM 2.2Ghz P4 i used to have.

Maybe its the sound card?
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Old 11-26-2013, 10:16 AM
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This is kind of a shot in the dark, since I haven't messed with DSD and this kind of thing in a couple of years, but do you have "disable all sound effects" checked in the sound control panel for your input device.. I seem to remember having a problem with that when trying.

Also, did you try adjusting the volume both on the scanner, as well as the sound input, again in the sound control panel, that was also an issue I had.
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Old 11-26-2013, 11:14 AM
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Quote:
Originally Posted by RC286 View Post

Maybe its the sound card?
It can also make quite a difference whether you have dedicated line-in vs combination line-in/mic port.

My laptop with mic-only seems useless.
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Old 11-26-2013, 11:27 AM
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I have a dedicated line in, thats what I use, all effects/"enhancements" are turned off.
I have tried both the line in and the mic input with the same results.

volume control on the scanner has no effect as it is a direct discriminator tap. I run the volume all the way
down on the scanner. Hearing the digital noise through the speaker is annoying. :P
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Old 11-26-2013, 11:54 AM
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How is your signal? Clear without a hint of static? Are you close to the source? I found even a hint of static can be an issue.
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Old 11-26-2013, 11:59 AM
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Quote:
Originally Posted by RC286 View Post
Hearing the digital noise through the speaker is annoying. :P
Yea, I'm remembering now that you mention it lol
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Old 11-26-2013, 12:18 PM
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Signal is clean, I connect it to my longwire antenna when I'm in the house. Doesnt make a difference though. I must be doing something wrong :P
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Old 11-26-2013, 1:03 PM
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Have you tried different control channels/towers.. I tried using the main CC from a tower which was giving me 70-80% signal(main tower for Halifax area which I listen to normally), and it wouldn't work, but once I used the CC from a tower just a bit closer(4-5 KMs difference from my location), with 85-95%, DSD came to life.
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Old 11-26-2013, 1:51 PM
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Default DSD Decoding

As previously mentioned your signal strength must be solid with no fluctuations.
I noticed that you said that there is "transistor noise" in your speaker when there is no signal. This is an indication that you have the input level to DSD too high (the scanner volume should not have any effect if you have a true discriminator tap) so lower your line in level as low as possible and see what happens. I assume you have a suitable blocking resistor in your discriminator tap.

I have a triple core computer that DSD did not work well on even though I have DSD running fine on other computers even an old Celeron. Recently I installed and old sound card and now DSD is decoding perfectly.
It seems that the on board sound just did not handle DSD very well, don't know why.

Good luck,

Mike

Last edited by mmisk; 11-26-2013 at 1:54 PM..
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Old 12-05-2013, 10:44 AM
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Default BC246T Discriminator

Just throwing this out there , but is the tap on there good? One if mine came loose one time and it wouldn't decide the pro voice here using dsd for crap.


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