LASD: Carson Trunking noise heard

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cj5

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While scanning the conventional channels of LASD, sometimes when a Carson sheriff unit ends transmission, the carrier goes over to trunking digital noise. It's not P25, it just sounds like analog trunking audio. Is this just interference, or is there a subsystem on the sheriff system that isn't in the database? Any ideas on this?
 

cj5

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This needs a bump, because I think folks missed it.

Anyhow, at about 1830 UTC today, I heard South LA as well as Carson sheriff channels broadcasting a lengthy trunked tranmission. Does anyone know of any system changes to LASD that would involve trunked radios? Or is this just bleed over from another system?

Usually I'll hear the officer with traffic to dispatch, dispatch comes back with traffic immediately, then it goes to a long trunking digital sound, and finally the broadcasts clears.
 

markclark

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cj5:

Referring to the 480 Mhz system only: That noise is the digital identifier. It identifies the unit and radio transmitting. Sometimes the sound it is a kerchunking noise, but usually it sounds distinctly digital.

Referring to the 800 Mhz CWIRS system, I haven't noticed any unusual noise on the Sheriff's radio patch. But I'll be listening.
 

cj5

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By digital ID do you mean the CTCSS or DCS? This definitely is not that type of sound. I can affirm that this is 100% a trunking digital sound. It sounds just like the stuff I hear on Orange County's CCCS when not in trunked mode. Unless of course LASD uses a special type of identifying mechanism. Thanks for listening out.
 

LAflyer

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What frequency are you picking this noise up on? Dispatch-9 or L-Tac5?

Listening from my location sounds 100% OK and typical LASD.
 

markclark

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cj5:

I mean that the noise is a burst of digital sound at the end of the transmission that is distinctly a digital or kerchunking sound. If that is what you are hearing that is the digital identifier, if not I don't have a clue what the sound is. I have also heard that sound at the beginning of mobile transmissions as well, however, the sound is filtered out when listening to the repeater side of the channel.

In the alternative, your scanner may not be cutting out the final EDACS tones at the end of each transmission. I hear that sound as well from time to time. There is a delay setting on my scanner to correct that problem (Grecom PSR-600). I'm not sure about your scanner, or its range of settings; you may want to address that question to your particular scanner forum. Good luck!
 
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cj5

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What frequency are you picking this noise up on? Dispatch-9 or L-Tac5?

I hear it on L-TAC mostly (as I don't have Carson's DSP programmed). Today I heard it actually on top of the LASD traffic again (Carson L-TAC). This time though it was a guy speaking Spanish the entire time. Any thoughts on that? That sounds like interference to me.
 
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dgower

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I listened for a couple of days during day shift on my work radio (XTS5000) and didn't hear anything like that at all. Just typical traffic. For what that's worth.
 

inigo88

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Guy speaking Spanish? You're getting intermod interference from a transmitter close by. Try using your scanners attenuator.

When you guys say the "digital identifier" are you talking MDC1200, or do they use a different format?
 
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