Culver City, CA PD - Just Got a Laugh - Sadly I Agree - Digital / ICIS

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BoboPinky

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June 17, 2012 at approximately 1810hrs.

Two officers on the main primary frequency trying to coordinate. "10-9, you were garbled...10-9, 10-9...", the other officer comes on and says, "... our wonderful radio system!"

HA! I've gotta laugh. Why? Well, yes, yes, I understand all the benefits of "digital / trunked" radio, but I also can't stand to listen to it. Look, face it, it sounds like crap. My involvement? Well, I'm not a "pro" by any means, but a scanner buff for more than 30 years, an amateur operator for almost 20 years, and a D-Star user for a few years (I don't operate that mode often, because it doesn't work! Reflectors dropping off, "R2D2" constantly, etc.).

Culver City, CA is ICIS, and has been true digital / trunked since the first of the year. I live in CC, and monitor quite a bit. Yes, I am "only" listening with a GRE800, not a "professional radio", but I must say, the amount of unintelligible, garbled communications, followed by "10-9" on Culver City radio (ICIS) is almost scary.

Its just like digital cell phone technology. Yep, I've got one, but it really is a joke (Verizon in Los Angeles). We happily PAY for dropped calls, and garbled / digitized communications? Would you put up with a car that just STOPS in the middle of the road randomly?

Digital radio is not what it should be. Maybe some day, but not now.
 

Clark

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My Uniden BCD396XT decodes the digital signal of Culver City better than my PSR500. I don't know why.
With the two placed side by side, sometimes the PSR500 is garbled and the BCD396XT sounds perfect on the same traffic.
I am in Mar Vista, only a couple of hundred feet from the Culver City border at the West end.

Clark
 

michaeldim

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It has to be the simulcasting that causes this issue. I know I was in Florida some time ago, and where I was staying they were on a conventional (read: non-simulcast) system and every transmission came through as clear as crystal. Literally the best quality audio I have heard out of my PRO-106 since I got it.

Then I come home back to my simulcast system and everything sounds like garbled, poppy, mud.
 
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kv5e

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Isi

Simulcast systems will have delay spread due to the propagation delay from more distant sites. When the same digital signaling is received at near equal power or within a few dB from more distant sites, then the decoders start struggling with the symbol recovery.

The deviation control for phase one systems transmits two bits per transition and when the delay from distant sites approaches 1/4 symbol width, then the delay spread greatly increases the BER/CWER.

Simulcast systems must have more sites at lower HAAT, greater downtilt on the antennas to reduce the radiation on the horizon, and frequency offsets on the carriers to mitigate amplitude nulls on the beating carriers so that the beating does not alias with the codeword and sync patterns if possible.

Simulcast design is a black art and not all implementers can do an effective job of coverage with minimal delay spread problems.

Craig KV5E
 

BoboPinky

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My Uniden BCD396XT decodes the digital signal of Culver City better than my PSR500. I don't know why.
With the two placed side by side, sometimes the PSR500 is garbled and the BCD396XT sounds perfect on the same traffic.
I am in Mar Vista, only a couple of hundred feet from the Culver City border at the West end.

Clark
In this case, it had nothing to do with my gear, it was the officer himself that made the comment on the air, about "our great radio system"!
 

Clark

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Venice, Calif
Were you able to hear the traffic that the officer said was garbled ?

The ICIS system is a very complex system but I haven't heard any comcomplaints from the Culver City users except maybe when the officers are on a special operation and way out of the city and in a marginal area.
Then somtimes they go to their "Freq. 10" which is a low powered non-trunked frequency.

Clark
 
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