Centereach FD repeater on public frequencies? - need help

[dave3825]

However. Intrigued by the FCC license stating the FD has something on the water tower in centereach. That seemed interesting.

There are many agencies/entities that have stuff on water towers. Its all about height. CIFD has something on the federal courthouse as well as others.

 

[o0BusySignal0o]

Yes. Of course. Absolutely.

I was intrigued that - maybe it was a RF relay from the Firehouse to the Water Tower - and wondering if something like that could be what OP is hearing.

But in about 72hrs or more of monitoring from a few locations - I’m not seeing any firehouse audio on that frequency.

 

[kayn1n32008]

Video proof: Centereach FD on GMRS 22 Repeater input.mp4

You are hearing the OUTPUT of the fire repeater on the 467MHz GMRS frequency, not the mobiles. I would suspect it's some sort of mix, or an image.

I don't use scanners, so I don't know what the Uniden IF frequencies are, how ever, I suspect if you subtract the IF frequency from the repeater output, it will land somewhere close to the GMRS frequency.

Intermod should not be 100% clear communications with a readable DCS tone.

I've had an analogue LMR repeater output and Connect Plus control channel mix, with the mixing product being the output of a ham repeater. Both the analogue and ham repeater using the same PL tone, causing my receiver to open up, because the PL tone was valid.

Using simple formulas (2a+b and 2a-b) from your previous email we calculate the intermodulation.
For the input frequency Intermod
2(f1−f2) 2×467.725−479.8625 = 935.45−479.8625 = 455.5875 MHz
2(f2−f1) 2 × 479.8625 − 467.725 = 959.725 − 467.725 = 491.8625 MHz
While this should be sufficient, as these are the inputs of CFD and Selden Radio repeaters as you can clearly see that Intermod is NOT the issue, I will do the listening frequencies too.

2(f1 − f2)

2×462.725 − 476.8625 = 924.4125 − 476.8625 = 447.550 MHz

2(f2 − f1)

2 × 476.8625 − 462.725 = 953.725 − 462.725 = 491.000 MHz

Also, keep in mind that UHF TV channel 23 center frequency is 490MHz, no idea if it's in use near you, but that could be causing problems too

 

[kayn1n32008]

I would say yes, some combination of field units and the repeater are incorrectly or sloppily programmed by whatever contractor did the work for Centereach.

I would wager a $5 bill none of the fire radios or the repeater is improperly programmed.

 

[ff026]

Is this all based on a scanner or a properly aligned receiver?

 

[KevinC]

Would this be what you were looking for?

CFD Output with input GMRS.mp4

drive.google.com

Since you appear to be using a BCT15X as your test radio try to apply "IFX" to that frequency and see if you still hear them.

 

[gatekeep]

You are hearing the OUTPUT of the fire repeater on the 467MHz GMRS frequency, not the mobiles. I would suspect it's some sort of mix, or an image.

I don't use scanners, so I don't know what the Uniden IF frequencies are, how ever, I suspect if you subtract the IF frequency from the repeater output, it will land somewhere close to the GMRS frequency.


I've had an analogue LMR repeater output and Connect Plus control channel mix, with the mixing product being the output of a ham repeater. Both the analogue and ham repeater using the same PL tone, causing my receiver to open up, because the PL tone was valid.

Also, keep in mind that UHF TV channel 23 center frequency is 490MHz, no idea if it's in use near you, but that could be causing problems too

Assuming the IFX feature isn't used on the BCT15X, per Uniden's information, IF specifications for that scanner:
- 1st IF at 380.7 - 380.8mhz / 265.5 - 265.6mhz
- 2nd IF at 10.8mhz
- 3rd IF at 450khz

 

[KevinC]

Once you test out the IFX feature we can discuss your link budget. Such as is the 15' vertical separation from the rad center of the antennas or ???

 

[o0BusySignal0o]

Being local to the area - I was intrigued by the possibility of this - however I have yet to see it on the SDS100 or multiple remote SDR sensors or even my own radio...

Interesting experience for sure.

 

[KevinC]

Since you appear to be using a BCT15X as your test radio try to apply "IFX" to that frequency and see if you still hear them.

I know people have lives outside of RR, but it would be nice if you'd provide an update on trying this.

 

[GTR8000]

Last seen Aug 2, 2025

I suspect he probably gave up after realizing he wasn't going to get the answer(s) he wanted to hear.

 

[KevinC]

Last seen Aug 2, 2025

I suspect he probably gave up after realizing he wasn't going to get the answer(s) he wanted to hear.

Sadly that's probably true. He had his mind made up before coming here.

 

[ff026]

Sadly that's probably true. He had his mind made up before coming here.

Another keyboard tecknishun, was he basing all of his problems based on a scanner?

 

[W1KNE]

Sadly that's probably true. He had his mind made up before coming here.

Another keyboard tecknishun, was he basing all of his problems based on a scanner?

He had all the answers himself, despite us giving advice, he would immediately correct them.

Probably just posting to stroke his own ego or something.

 

[KevinC]

Since the OP isn’t coming back, by default I’m saying IFX made the issue disappear. 🫠

 

[kayn1n32008]

Since the OP isn’t coming back, by default I’m saying IFX made the issue disappear. 🫠

Got to love it. Didn't hear what he wanted, so he took him self home.

 

[rr60]

Since you absolutely are sure, verify your belief. Go to the sites and verify using what RDF tools you may have.

What you believe may or may not be true. This is the way forward. Good luck.Out.

I was over this way back, over and out.