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Garbled P25- encrypted?

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Wilrobnson

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I should be able to figure this out, but it's late and I'm stupid.

On my new (today) PSR500, I found a few fed channels that I know to be part of a large TRS.

The radio displays an NAC of 718 in search mode, and the audio is just garbled noise.

Now, reading what I have about NACs, I get the feeling that's just silly.

And what's with the garbled audio? Is this what encryption sounds like over this radio?
 
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commscanaus

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Hi Wilrobnson!

On the PRO96- encrypted P25 sounds horrible and LOUD. Some folks describe it as R2D2 underwater! The decoder in the scanner cannot make sense of the bit stream because the information contained within it is jumbled up as a result of being encrypted- so all you hear is the garbled nonsense that the scanner's decoder has passed to the speaker.

Other reasons for garbled audio could be you have a poor signal and the bit error rate is too high causing the scanner's decoder to lose audio information. You could also have a nearby source of interference.

I am willing to bet that what you are hearing is indeed encrypted.

In my experience- NAC has little to do with encryption- as it is more of a form of digital squelch much like CTCSS on an analogue channel.

Commscanaus.
 

KB1KBD

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Please explain what you mean by the NAC is "silly". If you mean it was silly that an encrypted signal also had a NAC code it is not really. A NAC code prevents the squelch from opening unless the transmission includes the matching NAC. This helps to prevent receiving transmissions from another agency that is using the same frequency.
 

N8IAA

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Wilrobnson said:
And what's with the garbled audio? Is this what encryption sounds like over this radio?
Yes. It is a different sound than digital hash at the beginning or end of a transmission.
Larry
 

Wilrobnson

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KB1KBD said:
Please explain what you mean by the NAC is "silly". If you mean it was silly that an encrypted signal also had a NAC code it is not really. A NAC code prevents the squelch from opening unless the transmission includes the matching NAC. This helps to prevent receiving transmissions from another agency that is using the same frequency.
I meant the NAC code. Now, the next day, I realize that is a possible NAC code, at the time I just thought there were only a few dozen, not nearly 5,000 possibles.
 

K2QI

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I got a hit on the NYC FBI channels today, and that's pretty much what it sounded like... garbled transmission as if the speaker was talking under water.
 
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