Troop B: Sometimes not hearing headquarters -- encryption??

[fog]

Is Troop B (154.935) running 'normal' P25, with no encryption? And do they use a repeater? 95% of the time I can monitor them just fine, but every once in a great while, I can't hear responses from headquarters, and I'm wondering why.

This morning (Friday morning, 1:30-2am) I could hear an officer requesting license information, but no responses from headquarters. Since I was curious about what was going on, I opened the squelch on my first radio (VHF ASTRO Saber, set up for digital-only on Troop B's frequency) and was left just hearing a weird digital noise I've never heard before. It didn't quite sound like the usual noise of a P25 signal dropping out, but it was closer to that than any digital noise I've ever heard before.

Because the radio was set up for digital-only, and had no S-meter, I tried to tune them in on my analog-only mobile set. I'm not too familiar with the actual structure of a P25 digital stream, but headquarters sounded a bit different than P25 audio (in analog) usually does. It was almost more like static than a P25 signal. It pegged my S-meter, so it's definitely not an issue of headquarters having a bad signal. (But I'm almost positive they use a repeater anyway, so it'd be a moot point.)

Anyone know what's going on? My best guess is that it's some sort of encryption that headquarters runs part-time, but I only hear it once in a blue moon (and they don't seem to be relaying overly confidential information?). The officers seem to be able to hear them fine, but I can't. Has anyone else had the same problem, and can anyone confirm/deny that they're testing out encryption?

 

[Asmitty0010]

I get the same thing from Troop F. I don't understand it. I use three different freqs. to monitor Troop F. LP North which is analog, and there primary P25 ch. which is 152.630 from Twin Mountain Headquaters. LP north i can hear just about everything. When they are using the APCO25 i hear a few words then it goes blank. I also monitor there repeater off of Mount Washington which is anaglog I think. That, for the most part, i pick up everything.

They must do something w/ their APCO25 because I have the same problem. If anybody knows more than I do I'd like to know too.

- Stay Safe,

Alex

 

[Forts]

What type of scanner are you using? I know with my Pro-96, when listening to conventional P25 comms if one party is encrypted, you still hear the encrypted audio (but it's all jibberish of course). It almost sounds like you are missing a frequency, but that doesn't seem to be the case from what I can see. All I can suggest is make sure your DSP firmware is up to date on your radios... Oh, are the officers using MDT's perhaps? Maybe that's the data noise you are hearing. Just a wild guess on that one....

 

[fog]

What type of scanner are you using?

Running 'the real thing,' a Motorola ASTRO Saber handheld.

Oh, are the officers using MDT's perhaps? Maybe that's the data noise you are hearing. Just a wild guess on that one....

That's something I wondered at first. You can hear the officers speaking, but not headquarters, so I initially wondered if dispatch was responding via MDT. (Which would be a little odd.) But there's clearly a 'conversation' going on and I'm only hearing one side.

FWIW, this never happens during the day. I've only noticed it after work, specifically after midnight. (Never tried late night before midnight, though, so who knows when it starts.)

The mystery grows... For those of you experiencing the same problem, is it only happening at night for you?

 

[Forts]

Wow that is odd. It would be interesting to hear from someone with a digital scanner, and see if they experience the same thing. Gotta love a good mystery!

 

[skbnh]

Went down thru troop B area around 6am and they were running encrytion. Came back thru mid-morning and both base and cars in the clear. Also a few weeks ago during the day all was in the clear.
Steve

 

[zerg901]

Forts - does the encrypted P25 sound like giberish or like static on your Pro-96?

On a second note - perhaps the dispatchers are switching transmitter sites when they do the replies to the cars.

Peter S

 

[LPD7]

I herd troop B P-25 Encryption it sounded like normal P-25 bu tsounded like it was chopped in to pieces and spit to the barrax

 

[garys]

I herd troop B P-25 Encryption it sounded like normal P-25 bu tsounded like it was chopped in to pieces and spit to the barrax

That's not encryption. That's just poor signal as I heard it this evening. If you are listening in a Uniden scanner you probably won't hear anything the "ENC" will show on the display. Troop B sounds choppy compared to Troop A which I also hear fairly regularly.

Gary

 

[LPD7]

Thank Gary,

I always thought it was wierd that I got troop D in Concord W/O anything wrong with it. I also clearly Pick up Troop E sometimes and Belknap County Sheriff. I dont have a uniden but im just curious What does Encryption sound like? just so i can see the diffrence

 

[garys]

Thank Gary,

I always thought it was wierd that I got troop D in Concord W/O anything wrong with it. I also clearly Pick up Troop E sometimes and Belknap County Sheriff. I dont have a uniden but im just curious What does Encryption sound like? just so i can see the diffrence

DES on an other wise analog channel sounds like static with a few beeps thrown in here and there. I don't recall hearing any audio on an encrypted digital channel. I think that ENC just displays.

Variation in what you hear can depend on a lot of factors including tower height, out put power, weather, you name it.

Gary

 

[skbnh]

When I was driving down thru troop B area from my last post my 796 showed up as ENC on display and on return all was in clear
Steve

 

[LPD7]

I have a pro 96 and i herd DEA on CH-1 with what sounded like encryption and Hudson NH is partially encrypted so i kinda have an idea of what it sounds like but not 100%

 

[ctrabs74]

I dont have a uniden but im just curious What does Encryption sound like? just so i can see the diffrence

On an ENC transmission (at least on my 396), you will hear distorted audio for about 1 second (if that) then silence while ENC is displayed for the rest of the xmit.