MarkInTampa

One of my area ham radio clubs (they also run a great GMRS repeater) runs an event every month at a local park. Every month is a different theme, one month is QRP and the next may be GMRS but they always encourage GMRS users to come out and participate and always have a GMRS station setup. A few months ago they held a fox hunt theme with three stations. One GMRS, one 2m and one 70cm at different locations. I was out of town but heard they had a lot of fun.

The way I hear family ID's on GMRS goes something like this: First transmission: "(callsign) unit 1 to unit 2" Second transmission (responding radio) "unit 2 go ahead" Conversation between the to units but no ID since they know each other Last transmission "(callsign) clear" I don't think I've ever heard a family ID ever go on beyond 15 minutes.

Check out the Signal Identification Guide website at https://www.sigidwiki.com/wiki/Signal_Identification_Guide In particular the DMR, NXDN and the different P25 modes. Sound examples are on the webpage.

You should have tone on output of 467.700 not the input. The input tone of the repeater is the output tone of your radio.

The largest repeater in my area (462.575) has two receivers, primary on the standard +5 (467.575) and a secondary on 467.725. The repeater overlooks the port of Tampa and gets occasional interference on the primary input from ship traffic and they have shut it down. Unfortunately it confuses a lot of folks and a lot of radios (Midlands for example) don't support anything other than a +5MHz offset so they are unable to transmit to the repeater but receive it just fine. My Wouxun's (KG-1000 and KG-935) will allow for a different offset - as long as the TX offset is a GMRS frequency (including frequencies not assigned for repeater inputs like 467.6125) but a lot of radios don't. If your radios have dual scan or priority watch, what you can try (as long as the TX frequency is a standard GMRS frequency) is setup TX on whatever you want and RX as a 2nd channel on the dual scan or your priority watch channel.

Keep in mind that maritime users ARE allowed (even digital!) on the GMRS repeater input frequencies of 467.550 and 467.575 per ITU (not FCC) regulations but not the outputs of 462.550 and 462.575. They may affect (as they do in my area) the input of a 550 or 575 repeater mixing in with legit traffic even if on a different tone causing a bit of chaos on the output.

Like I said, your results may vary. The SWR on mine (again 2m/70cm version) is less than desirable on GMRS. However the GP-6NC GMRS version has as close to perfect SWR on GMRS (what it was designed for) as you can get and has a decent SWR across 70cm and 2m as well.

The GP-9 2m/70cm antenna sucks at GMRS, at least in my case. If you have a SWR meter or VNA test it out yourself, your results may vary....

You are about dead on on power loss. 59% according the the calculator, but with the gain of the antenna you have an effective radiated power of almost 200 watts. Keep in mind the tool I used (https://kv5r.com/ham-radio/coax-loss-calculator/) uses dBd for antenna gain, dBd = dBi - 2.15

I put a loop at the antenna because the Comet instructions tell you to do so. I figured if it is in the instructions, there is a reason why.

I did a tone scan and got a tone a few months ago when it was transmitting DMR and tried. Either analog is disabled or it's using a non-standard input. I did think about running a simplex repeater to mess with them but not worth the effort.

Here is one of them https://flscg.org/2021/03/tampa-gmrs-repeater/

It's close to impossible to hijack a encrypted DMR repeater that doesn't do analog.

Not in this case. The NXDN repeater went online six months ago, the P25 repeater has been online for a few years. I'm not complaining, both are really strong repeaters (the most dominant in the area) and most traffic is analog. If there is a bit of digital traffic a few times a month for a minute or two, it's a small annoyance for how good the repeaters are. The encrypted DMR repeater on .700 popped up a year or two ago. It was traced to a security company running illegally and has been reported to the FCC many times but it's still there.

Tampa has two digital/analog repeaters on GMRS, one running P25 and the other NXDN. The connection info is published on their websites and are public. Neither one of them get very much digital traffic, I would guess 95% is analog. There is also someone running encrypted DMR on 700 still, from what I was told it is a business running GPS tracking on fleet vehicle's. It drove the Tampa 700 repeater a year or so ago to .600 and they forced the existing .600 repeater in Clearwater to .550 knowingly but didn't care.