NYPD Radio Ops

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BigDogg795

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Ok,
First off, I'm not looking for any frequency inputs or the sort...my questions lies within the actual operation of the NYPD radio system; namely how in the heck two (or more) units are able to transmit at the same time.

My radio expertise extends no further than simple trunked or conventional repeater system, both of which I'm under the general understanding that if one radio on the system is keyed, nobody else (except by rare circumstances) can transmit and get through.

While monitoring the NYPD (usually on SOD), I find central is able to transmit at the same time as other units and I'm hearing both parties on my portable.

In layman's terms, how does this actually work?
 

auxscan

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Its a four wire system. The central dispatcher and a unit in the feild can can be keyed up and still talk at the sametime. Sometimes when you hear an "open mic" the central dispatcher can be heard since they are pushing out more wattage then the 5 or 4 watt portable.

If you have two frs radio and one gmrs bubble radio. key both the frs radio on ch 1 then key the gmrs radio on the same channel. the gmrs will be heard even though theres two radios keying up at the same time. so the radio with higher watt and reception will be heard over any busy air.
 

hvscan

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Wirelessly posted (BlackBerry9530/5.0.0.328 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/105)

It's a great system and has been in place for many years. Central can be transmitting and an officer in the street can come over the air with an emergency and everyone on the radio will hear it.
 

ff026

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Its a four wire system. The central dispatcher and a unit in the feild can can be keyed up and still talk at the sametime. Sometimes when you hear an "open mic" the central dispatcher can be heard since they are pushing out more wattage then the 5 or 4 watt portable.

If you have two frs radio and one gmrs bubble radio. key both the frs radio on ch 1 then key the gmrs radio on the same channel. the gmrs will be heard even though theres two radios keying up at the same time. so the radio with higher watt and reception will be heard over any busy air.
Your in the ball park but not correct. All NYPD division's use 4 wire audio with voting. When you here central talk and a unit in the field talk at the same time, what you are actually hearing is the field units audio coming through the console's speaker and the dispatchers mic picking it up. Central listens to the input only, and the audio that central hears is coming from the Voting Comparator. The system is full duplex for the dispatcher, but not for the units in the field.

The reason it is 4 Wire audio is so if central is broadcasting a message and a unit in the field has an emergency transmission, the unit in the field can still be heard by the dispatcher. 4 wire audio is very common in public safety systems. It has nothing to do with wattage, when you here the repeated audio from a field unit and the audio from central it is all coming from the same repeater with the same wattage!
 

auxscan

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thanks ff

i guess i had it wrong. I thought that central was pushing much more wattage then the porable units. sorry for the mis-information.
 

zerg901

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The SOD dispatcher transmits on 470.83750. The cops in the field on the SOD channel transmit on 473.8375.

If you can mull that info over, and make it jive with the other info provided in this thread, you will start to see how the big world of radios works. Its a cool world.

Peter Sz
 

NYCRADIO

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esu sod transmits on 470.8375 someone stated they transmitted on 473.8375
 

auxscan

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Doesn't that mean the dispatcher needs to be close in order to be crystal clear. since her voice is not repeated? Maybe more more wattage the units in the feild? In a city like new york, Im suprised to see my gmrs radio go 5 miles on simplex.
 

ff026

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No the dispatcher and the voter are connected via microwave to the repeater. Units in the field use 2 watt portables. For almost every division there are a lot of receivers, which in turn are connected to the voter.
 

n2nov

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No the dispatcher and the voter are connected via microwave to the repeater. Units in the field use 2 watt portables. For almost every division there are a lot of receivers, which in turn are connected to the voter.
Private digital wired connections as well as microwaves.
 

kc2rgw

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A bit unrelated, but on ham repeater link systems you can arrange for a similar ability with the central repeater hub on the system. Some controllers allow you to mix the audio on your link radio ports.

So you have hub repeater with say three or four link radios, inputs from other repeaters that the hub re-transmits.

You can set some controllers to mix the audio of all the links so you can hear people at the same time if people on the remote links 'double' . However the hub repeater always has priority so if anyone comes in on the hub repeater input, it will just shut out the linked systems' inputs.
 

ff026

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A bit unrelated, but on ham repeater link systems you can arrange for a similar ability with the central repeater hub on the system. Some controllers allow you to mix the audio on your link radio ports.

So you have hub repeater with say three or four link radios, inputs from other repeaters that the hub re-transmits.

You can set some controllers to mix the audio of all the links so you can hear people at the same time if people on the remote links 'double' . However the hub repeater always has priority so if anyone comes in on the hub repeater input, it will just shut out the linked systems' inputs.
What you are talking about is totally different then what is going on in the NYPD system. The Voters in the PD system have a card called tone priority, which gives priority to the console.
 

ff026

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EDIT: Actually its the repeater that has the tone priority module not the voter, thats what happens when i try to think at 5 30 AM.
 
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