Washoe County System: CC on Input Freqs?

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Dave_D

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Hi all,

A few weeks back, I overheard control channel data on two of the Washoe County System's input frequencies, 821.6 and 823.7. It was noticed only briefly, while cresting Mt. Rose on US 431. Haven't heard it again since. What could this mean?

Any input is greatly appreciated.

Dave
 

wlmr

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Dave_D said:
Hi all,

A few weeks back, I overheard control channel data on two of the Washoe County System's input frequencies, 821.6 and 823.7. It was noticed only briefly, while cresting Mt. Rose on US 431. Haven't heard it again since. What could this mean?

Any input is greatly appreciated.

Dave
As just a guess, could you have actually been picking up mobile/portable voice radio traffic transmitting into the system? Is this a digital or analog voice system?
 
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Dave_D

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It's an EDACS system with unencrypted analog voice.

I suspect you're right, that the signals originated from a mobile radio. That said, the signals were intercepted only while in close proximity (maybe 1k-3k feet) to the towers atop Mt. Rose. In fact, I first dismissed them as "Close Call" hits before realizing otherwise. [I was distracted by that pesky driving thing. And a good thing too; inattentive driving on Mt. Rose Highway can be hazardous to your health.]

Any ideas?
 

wlmr

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Dave_D said:
It's an EDACS system with unencrypted analog voice.

I suspect you're right, that the signals originated from a mobile radio. That said, the signals were intercepted only while in close proximity (maybe 1k-3k feet) to the towers atop Mt. Rose. In fact, I first dismissed them as "Close Call" hits before realizing otherwise. [I was distracted by that pesky driving thing. And a good thing too; inattentive driving on Mt. Rose Highway can be hazardous to your health.]

Any ideas?
I don't know the geography you're referring to (not in Nevada) but your phrase "atop Mt. Rose" may mean that you had really good line of sight receiving conditions to mobile radios out yonder somewhere. So far you haven't poked any fatal holes in my initial theory/guess. From the sounds of it, your Mr. Rose Highway sounds like the type of location where attention to driving is first, second, third, etc., with scanner stuff way down the list of things to pay attention to. :)

edit: Just read your info stating ANALOG voice, which kinda throws out most mobile signals with the possible exception of inbound traffic for the system's control channel. Do the freq's match up with as being exactly 45MHz lower than the known control channels in that area?
 
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Dave_D

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Yes, 821.6 and 823.7 are absolutely input freqs for the system.

I never really thought about how mobile radios communicate with the site controller. I presume that every mobile radio in a system sends its requests-to-transmit on a frequency 45Mhz below the primary control channel, right? If so, then these data bursts should've been on 821.9 or 821.3. [The system has two primary control channels.] Or, on 821.275 or 821.575. [Two alternate control channels.]

But then, those data bursts were far too lengthy to be requests-to-transmit. As I understand it, a request-to-transmit lasts only a few milliseconds. These lasted several seconds apiece. Though I repeatedly hit the scan button to skip 'em, they kept coming back.

I'm not aware of any other reason a mobile radio would transmit large chunks of data. Does a mobile data terminal sound like a control channel? Maybe our local sheriff acquired some MDTs.

There's excellent reception atop Mt. Rose. And this would jive with your suggestion of a mobile radio, being that the signal was strong right up until I crested the mountain, at which point it dropped off abruptly. Had it come from the towers, it would've likely continued.

I'm still stumped. Don't know enough of how trunked systems work to wager on any more guesses.

Dave
 
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