FDNY UHF Frequencies

When listening to the FDNY UHF's (dispatch) I noticed there seems to be a lot of signal drop outs. My signal meter shows a full 5 bars but then for a split second it completely drops out and then comes back again. What would cause this? I'm using an outdoor antenna and I'm only 10 miles outside the city. I have no problem picking up the NYPD frequencies.

ansky said:

When listening to the FDNY UHF's (dispatch) I noticed there seems to be a lot of signal drop outs. My signal meter shows a full 5 bars but then for a split second it completely drops out and then comes back again. What would cause this? I'm using an outdoor antenna and I'm only 10 miles outside the city. I have no problem picking up the NYPD frequencies.

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I have the same problem out here in Ct. monitoring them. Just for comparason, it may seem like I am pretty far away, but I can hear just about 100% of the NYPD precincts here. I am in a high spot over the L.I. Sound. Even the precincts that I receive weak, like the Statan Island ones, their signals stay constant. But with FDNY UHF freqs they fade up and down as you say. I guess it has something to do with the way they transmit lower power from many different sites. I don't know the real answer. I just figured I would chime in here and let you know that you are not alone. I get the same fading phenomena with the Suffolk County trunked system. And they are right across the water from me. I can take the antenna off of the scanner and still get the system. But the signals constantly fade around. But take a trunked system like NYC DOITT on 800 mhz. or the New Jersey State PD system, and they don't fade at all regardless of how weak they might be coming in to me.
Bob
Milford, Ct.

It is probably due to the type of system in use, as described in the data base statement below:

The FDNY dispatch frequencies are not repeaters in the traditional sense, instead it's a full duplex system with voted receivers and a mixer.

I live in Nassau County snd although I don't monitor the FDNY UHF system very often, when I do I get the same spontaneous drop-out problem too. Glad to know I'm not the only one.

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W8RMH said:

It is probably due to the type of system in use, as described in the data base statement below:

The FDNY dispatch frequencies are not repeaters in the traditional sense, instead it's a full duplex system with voted receivers and a mixer.

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Can someone clarify what a duplex system means?

The FDNY and NYPD use very similar systems with voting receivers and mixers. You can read more about the NYPD's setup here- http://forums.radioreference.com/new-york-radio-discussion-forum/170013-nypd-radio-ops.html

I think it has more to do with fdny's uhf frequencies being in close proximity to each other (narrowband). When more than one borough is transmitting at the same time, you get slight interference.

I haven't checked lately, but when at work when I go on the roof I can hear FDNY UHF with out any issues. Mainly Manhattan and Queens.

You do realize that they are just taking the VHF frequencies and rebroadcasting them on UHF.

radioman2001 said:

You do realize that they are just taking the VHF frequencies and rebroadcasting them on UHF.

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Actually they are not. When a new rig is delivered it has a UHF mobile installed in it. The info has been posted on this board before. They are running 2 different systems linked together right now.

ff026 said:

Actually they are not. When a new rig is delivered it has a UHF mobile installed in it. The info has been posted on this board before. They are running 2 different systems linked together right now.

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True.

And the older rigs are also equipped with UHF mobiles. About a year or two ago the radio mechanics went around completed that upgrade.

I'd say 95% or better of the fleet have had their mobiles switched to UHF. There are some support vehicles that still have VHF mobiles as well as some chiefs and special units that have portables radios used to talk to the dispatchers are still VHF.

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cackis said:

I'd say 95% or better of the fleet have had their mobiles switched to UHF. There are some support vehicles that still have VHF mobiles as well as some chiefs and special units that have portables radios used to talk to the dispatchers are still VHF.

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I completely agree with cackis

Sounds like a voted system, with transmitter steering. Would give the results the OP is talking about. Just a guess though. I know nothing about tech details of there system.

Good news that they are complete on the UHF system, but as usual there will always be a few vehicles that either got lost in the shuffle or was not done due to age or being retired. I remember having a Low Band GE Mastr radio in one of my old ambulances years ago (1980) on what became the Coroners system even though NYCEMS had moved from VHF-Hi to the UHF-T system 5 years earlier. I never did figure that one out.
I hope they don't have a voter steering system, as I have never seen a voter transmitter steering system that worked properly, and provided good coverage for the user at the time he was calling in. Usually it would steer to the wrong transmitter, because he voted a site not in his area, or someone else would key up and reroute the transmission to the wrong area. I actually removed a few because of those complaints, and a simulcast transmitter system would work a lot better.
I'll have to talk to when I can someone in their radio shop, as I don't normally monitor just FDNY all day to hear the problems reported, I prefer to listen to Westchester Co's 3600 system.