Calfornia Dept --not--going 800 Mhz

[brey1234]

With everybody tripping over themselves to go 800 Mhz--Here's a California police department that's taking another route.


Communication will soon get a lot easier for the Manteca Police Department.
The City Council Monday night appropriated $1.2 million in bonus bucks — fees developers pay per home to guarantee sewer allocation certainty — for the purchase of a new department radio system.
“This system will take us into the 21st century,” said Police Chief Charles Halford. The new plan would move all Manteca public safety agencies to the UHF, or 450 megahertz bandwidth, along with the eventual conversion to a 450 trunked system for all public safety agencies in San Joaquin Valley.

http://www.mantecabulletin.com/articles/2007/03/06/news/news3.txt

 

[karldotcom]

Kind of what LA County is planning... When they say ALL agencies in the Valley...do they mean all the way down to Bakersfield?



>>>along with the eventual conversion to a 450 trunked system for all public safety agencies in San Joaquin Valley.

 

[zz0468]

Good for them. After playing on 800 MHz for the last 20 something years, I've come to the conclusion that it's the wrong piece of spectrum for public safety, at least in a rural environment.

 

[ScannerDude244]

Good for them. After playing on 800 MHz for the last 20 something years, I've come to the conclusion that it's the wrong piece of spectrum for public safety, at least in a rural environment.

isn't most of the SJV flat? I know 800mhz wouldn't do good here in Monterey County hills everywhere.

 

[gmclam]

I wouldn't consider Manteca to be rural. That area seems to be getting more crowded (with people) every day. While they may not be going to 800 MHz, I see they're still going trunked in lieu of conventional.

 

[mkewman]

what kind of trunking.... thats the real question

 

[Benmin]

Yup!

isn't most of the SJV flat? I know 800mhz wouldn't do good here in Monterey County hills everywhere.

Good Point. They have it set up well now!

 

[zz0468]

isn't most of the SJV flat? I know 800mhz wouldn't do good here in Monterey County hills everywhere.

It's not so much a matter of whether the terrain is flat or not. It's really more a matter of cost vs. expectations. The cops want portable coverage everywhere they go. At 800, it takes a lot more sites to provide that than it does on highband or UHF. In a rural county, it doesn't make sense to build 15 or 20 sites at a $million plus per site, when a different frquency range works as well with 5 sites. It's politics driving departments to 800 MHz, not physics. I know of a few cases here in California where the engineers made the decisions. 800 is NOT where they ended up.

 

[N_Jay]

. . . It's politics driving departments to 800 MHz, not physics. I know of a few cases here in California where the engineers made the decisions. 800 is NOT where they ended up.

You are jumping to conclusions in a few areas.

It also depends on the number of channels available in each band.

It also depends on the desire to implement the new system without interrupting existing operations.

It depends on the availability of equipment providing the features the users needs.

Reliable portable operation often requires almost the same number of sites on any band.

 

[zz0468]

You are jumping to conclusions in a few areas.

It also depends on the number of channels available in each band.

It also depends on the desire to implement the new system without interrupting existing operations.

It depends on the availability of equipment providing the features the users needs.

Reliable portable operation often requires almost the same number of sites on any band.

No, I'm not jumping to conclusions. I am specifically *NOT* talking about all the items you mention. I am categorizing all of those under "politics". Now, don't be pedantic and pick at the definition of politics here. I know I am making a broad general statement putting things like channel availability into that category. Never mind all that - I am specifically discussing the behavior of RF, and it's suitability to provide coverage.

In regards to the items you mention, for the most part, you are correct. I do disagree on your statement that different bands require the same number of sites. That's simply not true. After having spent many many years doing coverage design for large simulcast systems, I've learned just how differently rf behaves at various frequencies.

The way signals refract and bounce varies with frequency. Attenuation from trees varies with frequency. Weather impacts various bands differently. That’s not to mention free space losses. In my experience, when all that is added up, I've found 800 MHz to be a poor performer in comparison to other choices. In an urban environment where sites can be concentrated around a relatively small area, it can be ideal. In the desert and mountains where site availability can be limited because of environmental concerns, it's not so hot. 30 mile spacing between sites won't cut it at 800, but can work just fine on VHF.

 

[gmclam]

I totally agree with zz0468

In regards to the items you mention, for the most part, you are correct. I do disagree on your statement that different bands require the same number of sites. That's simply not true. After having spent many many years doing coverage design for large simulcast systems, I've learned just how differently rf behaves at various frequencies.

The way signals refract and bounce varies with frequency. Attenuation from trees varies with frequency. Weather impacts various bands differently. That’s not to mention free space losses. In my experience, when all that is added up, I've found 800 MHz to be a poor performer in comparison to other choices. In an urban environment where sites can be concentrated around a relatively small area, it can be ideal ideal. In the desert and mountains where site availability can be limited because of environmental concerns, it's not so hot. 30 mile spacing between sites won't cut it at 800, but can work just fine on VHF.

I totally agree with zz0468

 

[N_Jay]

No, I'm not jumping to conclusions. I am specifically *NOT* talking about all the items you mention. I am categorizing all of those under "politics". Now, don't be pedantic and pick at the definition of politics here. I know I am making a broad general statement putting things like channel availability into that category. Never mind all that - I am specifically discussing the behavior of RF, and it's suitability to provide coverage.

In regards to the items you mention, for the most part, you are correct. I do disagree on your statement that different bands require the same number of sites. That's simply not true. After having spent many many years doing coverage design for large simulcast systems, I've learned just how differently rf behaves at various frequencies.

The way signals refract and bounce varies with frequency. Attenuation from trees varies with frequency. Weather impacts various bands differently. That’s not to mention free space losses. In my experience, when all that is added up, I've found 800 MHz to be a poor performer in comparison to other choices. In an urban environment where sites can be concentrated around a relatively small area, it can be ideal. In the desert and mountains where site availability can be limited because of environmental concerns, it's not so hot. 30 mile spacing between sites won't cut it at 800, but can work just fine on VHF.

I agree with a lot of what you are saying.

While VHF can give you "usable" coverage over a wide area, especially with mobile equipment, to get high reliability (95%) with portable equipment, there is NOT a significant site separation difference. In addition with simulcast, there are site separation limits (especially with digital) that further negate much of the advantage of lower bands.
When you combine this with the real cost of finding and deploying multiple VHF channels (reducing site noise to an acceptable level, pairing channels acceptable, and implementing antenna combining and duplexing systems) the "obvious" choice does not always remain the best choice.

Even if you consider channel availability to be a political issue, it is still significant.

 

[code3cowboy]

not many people use digital radio in california.