Westchester County PD Radio Question

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pintopkp

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First off, I'm new to all of this, but I DID take the time to read a lot of the newbie FAQ's. However, it has left me with a question:

Regarding the county PD's radio system, is it a duplex system or a repeater system? I know the system uses repeaters (hence, repeater system), but when I look up the freq on radio reference (155.310), it shows it as "BM" (duplex operation). The explanation of a duplex system says it is different than a repeater system. I'm confused. I do know that with their radios they cannot talk/listen at the same time (which it states a duplex system can do) and it says a repeater system is a special kind of duplex system. Wouldn't that make it an "R" designation then? Sorry if this is a stupid question, but I find this stuff facinating. Thanks for any help!
 

SCANdal

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pinto,

Welcome aboard.

You are right. 155.310 should be listed as an R, not BM. Be aware that units can come up on simplex (a.k.a. "Direct") on the repeater output - WCPD's channel 2.

SCANdal
 

pintopkp

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Ahhh....I see. Thank you. I thought I was totally lost with all the definitions. I feel better now.
 

fineshot1

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pintopkp - welcome to a confusing world.

A repeater is a full duplex 2 frequency device. It transmits and receives at the same time but on 2 different freqs. This is possible due to alot of external equipment which I wont go into detail here explaining.

There are different types of duplex operation. There is also half duplex. Transmit & receive on the same freq but not at the same time. There is also transmit & receive on split freq not at the same time(some taxi base radios do this so the taxi mobiles cannot hear each other).

If you have a copy of "Police Call" it has some good basic descriptions in the front section.
Welcome to scanning.......
 
D

DaveNF2G

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Repeaters are not "full duplex" - that means telephone-like operation wherein all radios can transmit and receive at the same time.
 

pintopkp

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It is pretty confusing which makes me all the more interested in it. The county PD's system stinks and the coverage is awful (the Town of Cortlandt patrol is now dispatched by the TMC due to the crappy reception in the northern reaches of the county)! Then I hear departments like NYSP and Yorktown (especially Yorktown which I can pick up with the scanner function on the mobile in the car no matter where I am in the county) and I'm amazed at their clarity. That's what got me interested in scanning and how com systems operate. I wanted to know what makes the system such s**t!
 

ff026

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actually the dispatcher for westchester is FULL DUPLEX using 4wire audio out of the voter to the repeater.

pintopkp 4 wire audio is a process by where the audio received from the voter then sent to the dispatchers console and the repeater at the same time. if the dispatchers keys up during an incoming call the voter has a card in it call tone priority module and passes the dispatchers transmit audio to the repeater. when the dispatchers keys their console during an inbound transmission the incoming audio is heard on the select speaker and if you are listening on a scanner you can hear this.

a lot of the more properly set up radio systems have this feature.

4 wire audio is used on all NYPD channels except for the Tac channels. and all FDNY dispatch.

the FDNY dispatch system is actually a B/M BASE MOBILE the inbound audio is not heard until the dispatcher "turns it on"
 

archduke

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A "voter" is a comparison box that gets feeds from various "satilite receivers" all over the area and then the voter picks out electronically the best signal and passes only this best signal to the dispatcher or the repeater. If an officer was on a handheld in the northern part of the county his signal would be heard at the Mohansic site (if its still there) much better than at the Valhalla site. So the voter would accept Mohansic and ignore Valhalla and ideally the dispatcher would only hear the clearest signal.

The Westchester PD radio system has always been a disgrace, in fact when I return to the area and hear it I am embarrassed for the people who have to use it. Once about 30 years ago when the parkway police>county police were using a repeater pair on 155.55/159/xxfor their main ops and 155.31/158.xx for secondary ops they actually lost one of these repeater pairs because a new tower was built at the county jail in Valhalla and it was about 300 feet South West of the earlier tower and that put it too close by a few feet to another police user in mid state New Jersey. The NJ department brought this oversite up with the FCC and Westchester County lost.
 

ff026

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a voting comparator or voter is a piece of equipment that measures the best signal coming into a repeater and passes it to the repeater.

in a "voting" system receivers are spread around the area of coverage to improve the the talk in of units in the field to the repeater.

basiclly: the receivers send out a status tone of 2175 hZ, when a signal is picked up it drops the 2175 status tone and sends the voice down the line or over microwave, T1, whatever method is used. the Signal Quality Modules or SQM(pronounced SQWIM like swim with a Q) picks the signal with the best signal to noise ratio and sends it to the keying module which then keys the repeater and sends the voted signal over the air.

this takes place in milliseconds.
 

pintopkp

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I get it now. Thank you! So these voters are spread out in different sites than the repeaters or they occupy the same sites as the repeater? Seems like a whole lot of pieces to keep track of and repair (which they seem to do frequently). The Mohansic site is still there and in use (and apparently will be for the new Fire/EMS system too). I would have figured that the Mohansic repeater would transmit well into the town of Cortlandt though (which is certainly not the case).
 
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SCANdal

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pinto,

Negative. There is only one voter (aka "comparator") - which may or may not be located with the repeater.

What is spread out throughout a given coverage area are the 'satilite' receivers (meaning one or more receivers [base stations] that listen on the input frequency that are not at the repeater site) that pull in signals from field units (portables, mobiles, base consoles) that the repeater may or may not hear itself. The voter picks the best quaility signal (from a satilite or from the repeater itself) and allows that signal to pass to the repeater (and, if so equipped, the dispatch console) so that all the other filed units can hear it.

SCANdal
 
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APX8000

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What about a system with multiple repeaters on the same frequency ? How would that essentially be set-up ? I'd like to hear from the pro's like ff026 and SCANdal...

I've argued with my county over this for many years, especially on our EMS channel. I'm referring to the Orange County, NY 718 frequency.

In order to increase coverage in the county, they basically put up more repeaters. The output frequency of the repeater is 153.860 using PL 77.0.

The county has 5 different sites where the actual repeaters are located:
Beacon, Arden, Graham, West Point and Mt Peter.

The input frequency to the repeater located at each site is the same. The input PL however, is different so you only key the repeater you want. This works fine in some instances, but bad on others. Here is why...

I've called the county on one tower and they answer me on another. Fine if I'm in hearing distance of that other tower, such as when mobile, but on portable forget it...sometimes they answer on the tower located on the other side of the entire county. Needless to say on a portable they sound weak and low even though I sound 5X5 to them. I've also called on a radio check and they respond "loud and clear on all towers" when I'm only transmitting over one tower.

Reason being is their system is set up just like my radio, they have to select the repeater to talk on and all the receivers at the console are actually the repeater output instead of input (opposite of what NYPD, FDNY does), which is the same for all five towers ! So all lights will blink on the console for all towers instead of the one I'm calling on. Additionaly, if they are talking, field units cannot transmit, because they don't hear the repeater input. They hear it over the repeater output. When talking, it mutes the repeater input because they are using it to transmit to the repeater site and overrides mobiles and portables because of more watts and a better antenna. Poor design, poor set-up. No tie-line to the repeater such as T1 or microwave to key it from the dispatcher center, just 5 radios basically set up to talk on five different repeaters by using five different input PLs.

So how do you fix the problem? Could you change the console to listen to the repeater input instead of the output. This woudl have to be done to listen from the actual repeater site and not the center. Then use links from the sites to the center, whether it be microwave or UHF, etc? I'm guessing you would have to link it the opposite way to key the repeater site from the center as well.

What about a voted system with multiple repeaters?...would one be required at each site? I'm guessing no if you change the repeater input of all five towers to use the same input PL. This would put access to all repeaters over one channel. You have all five sites send the signal to the voter, which receives the best one and sends it to the best repeater and the console at the same time. Where do you locate the voter? How do you send that signal back to the repeater site as well as the console?

The dispatcher could then select the actual tower site that they are hearing the signal on and talk back to the unit in the field on the repeater output instead of input. But if all the towers are on the same frequency and PL, how do you tell which tower the signal is coming from ?

We want to eliminate field units from having to change channels when driving all over the county to be within tx range of the best tower. Just one channel to access all. And we want to elimate the dispatcher guessing the right tower.

How about a little help explaining how it's done for us novices? And what about a simulcast system so the best received signal gets transmitted over all the towers so someone on portable on one side of the county can talk to someone on portable on another side. The voted system without simucast could not accomplish that correct ?
 
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ff026

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you could do talk-back voting, dutchess county does it on there uhf system. talk-back voting makes all the repeaters receivers feed into a comparator and which ever has the best signal to noise ratio is the repeater that they transmit from.
you could do simulcast but it is way more expensive than talk back voting.
you could regionalize your repeaters using straight voting and get a new repeater pair(12.5 kHz only available).
what you need is a consultant independent of your present communications supplier to do a survey and figure out what is best, then implement their findings.

you can have the console linked to repeater by rtl(radio tie line) or microwave and do 4 wire audio so they can hear you on the input.

we hired a consultant here in rockland and have been working on our system for over 10 years and it is about to come to fruition very soon before the end of the year.
 
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