Channel spacing and older radios

[rtc1930]

Where it gets a bit dicey is when the FAST or Water Supply channels are used in close proximity to the fireground channels. The Water Supply channel is particularly troubling, as it's right smack in between two of the fireground channels with only 7.5 kHz spacing between all three.

You are correct that it was specifically the fire ground channel which interfered with the water channel. And of course both adjacent FG channels were in use. Arguably the circumstances of this much traffic in close proximity might of been rare but there is a push to use those channels in combination more frequently. I should be clear that none of this interfered with actual operations and might of been limited to a sub-set of radios which have since been taken out of service but was a lesson learned, at least for me, that they were that close.

I do need to check our mobiles to ensure they are set to low power on those channels but the issue that day/night was definitely on portables. It did seem that our new APX radios worked fine between the two channels in question so definitely questioning the setup / settings / tuning on the older HT radios. I didn't try our XPR radios yet to see if they fair better like the APX.

 

[GTR8000]

I get that spectrum is at a premium, but the county really should've done a better job trying to get some separation between these channels that are all potentially used on the same scene. Frankly, they ought to consider swapping the frequencies between FAST and water supply. You're going to be doing tanker shuttles a hell of a lot more often than FAST ops (thankfully). Oh yeah and if the FAST is activated, chatter on the FG channels should really come to a halt anyway to allow for emergency transmissions.

But yeah, without radios that are fine tuned and the modulation set for true narrowband operation, you're going to experience adjacent channel spillover.

 

[n3obl]

Might be time for the fire chiefs and the dispatch to sit down and consider assigning certain channels base on location to try and separate.

Also maybe consider reprogramming and change the pl tones on the freqs so it not all the same.

 

[GTR8000]

Might be time for the fire chiefs and the dispatch to sit down and consider assigning certain channels base on location to try and separate.

Also maybe consider reprogramming and change the pl tones on the freqs so it not all the same.

The problem with assigning FG channels is that the water supply frequency is only 7.5 kHz from two of the three primary FG channels, so you're going to potentially have an issue somewhere in the county regardless of frequency assignment. Changing PL tones only masks the issue, but underneath it all you're still operating frequencies spaced too close together in tight quarters, which is no bueno. They really need to get that water supply channel away from the two fireground channels, that's the correct solution.