berkinet

I believe (Ie. someone please correct me if I am wrong) that phenomenon is called tropospheric ducting and is different than skip.

GMRS is FM and so more likely to avoid the noise problems assosciated with AM services, like CB, especially CB in SSB mode. As for the mountains, the effect of elevation on IP packets is greatly overstated.

Nope, there is no skip on UHF, strictly LOS (Line Of Sight), with maybe a little bouncing off of good reflectors. It was most likely a case of repeaters being linked, probably over the Intenet. It is possible to create long chains of repeaters using radio links, but outside the ham bands that is not too common.

Probably... Walkie-Talkie generally is used to refer to the cheapo FRS radios. Of course, there is no US department of radio nomenclature, so you are free do use whatever terms you want, even if it does annoy the natives.

HT, from Motorola’s Handie-Talkie, or just Hand-Held, are commonly used terms. Welcome aboard.

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I don't see any ambiguity here. It seems clear "Fixed Stations" may not talk through a repeater and may use the 467mHz main channels. If you are having trouble following, here it is in plain text. Per 95.303 a fixed station may only talk to other fixed stations. and per 95.1763 sub c, a Fixed station is not allowed to transmit through a repeater, though it may transmit on the 467mHz main channel. The only issue is the definition of a fixed station provided by @jones. However, note that definition cites no actual rules and is in direct conflict with the citing posted by @PastorGary. As far as I can tell, unless someone specifically needed to use a 467 mHz main channel for direct communications between fixed points, and limit their power to 15 watts, there is no reason to ever declare a station as a fixed station rather than a base station. My guess is fixed stations would only make sense in areas where no repeaters were available. general line-of-sirte communications were possible and, for some reason, no other channels were workable .

Or, in more colloquial terms, as often ends up being the case, RTFM

A couple of random thoughts: 1) LMR400 is prone to intermod when used between a duplexer and an antenna. Especially if the coax is not new. 2) Are you certain the duplexer was tuned for GMRS in general, and your specific frequency in particular? 3) As noted already by @ZAP, these radios are VERY prone to blowing/burning the final. Running at a high duty-cycle will almost certainly blow the final. I would not run it any higher than 25w and they should really be run at as low an output as works for your needs. It sounds like you may already have a problem. 4) It seems you are testing with a field strength meter. Do you have a (good quality, like a Bird) meter and a dummy load you can use. That is the only way to get a reliable reading for the output.

By making lots of mistakes

Speaking of the antenna. I was curious why you chose the CA-712EFC over the CA-F72GF. While there is no real great difference between the two for GMRS, I picked the F72GF for a couple of reasons others might want to consider. Although there was a little extra work cutting the antenna to length I was able to tune it spot on to our transmit frequency. Also, because I had to open it anyway, I was able to seal it up nice and tight on reassembly and I had a chance to check all the internal solder joints as they have a (somewhat undeserved) reputation for problems.

We have a similar duplexer with a Motorola GR1225 installed on a residential roof along side a PV (solar) system. We were using the EIA audio filtering on the input (high pass) and adding PL back in on transmit. what we found was during very bright times of the day we were getting intermod coming back into the radio and holding up the repeater until the time-out-time (TOT) was reached. After changing coax (inside the box and the antenna feedline) and antenna, we have come to the conclusion the source if the signal is the PV and the intermod is being generated in the duplexer. The duplexer was well tuned by a pro so there is not much we can do except to add some cavities. Unfortunately, that is not economically feasible for the moment. In our case, since athe PV noise was not interfering with actual signals, we addressed the problem (I.e. we didn't actually solve it) by changing the transmit PL We could have also just passed PL (flat mode audio) but that effectively defeated the hang-timer and "over beep." YMMV

You may need to give some parameters. Dual banders run from under $15 to several hundred dollars. Do you want a display, dual display, dual watch or dual vfo, several battery options, ease of keyboard programming, CHIRP support, etc. BTW, since this was posted in the GMRS forum, I should note, and you probably already know, as far as I know, there are no dual band radios that are Part-95 certified. (at least not if you expect to have VHF & UHF access at the same time).

from Part 95(a) section 29... ( For a mobile station, control station, or fixed station operated in the duplex mode, the following 467 MHz channels may be used only to transmit communications through a repeater station and for remotely controlling a repeater station. The licensee of the GMRS system must select the trans- mitting channels or channel pairs (see §95.7(a) of this part) for the stations operated in the duplex mode, from the following 467 MHz channels: 467.5500, 467.5750, 467.6000, 467.6250, 467.6500, 467.6750, 467.7000 and 467.7250.

I believe that term applies to packet forwarding repeaters. For example, in an APRS network.

Well, and I write this never having used a simplex repeater, I don't think Zello (which I have used) is an applicable analogy). Zello works in real (or near real) time and retransmits the message directly to one or more people or groups. A simplex repeater is more of a store and replay device. It records the input and then re-broadcasts the input back out on the input frequency. Hope this helps and, hopefully someone with real experience will chip in.

Make sure you are using the latest "daily build" and note it is listed as a BTECH radio, not Baofeng.

Of course. I was using the term loosely to mean transceiver, or end user radio. The repeater's input and output were on FRS frequencies. So, they obviously used non-FRS equipment (i.e. something that could do a non-standard offset) to talk to the repeater.

Out of curiosity, I scanned the FCC enforcement records (URL below) and cannot find any enforcement actions based on equipment at all. That is not to say there aren't any, my search may have been faulty or they could pre-date the publicly available data. But, unless someone announces "Hey, how does my cool little Baofeng radio sound," as long as you are transmitting a clean signal with appropriate power, it is impossible to detect. OTOH, if you flagrantly misuse the service and the FCC van roll up outside your door and they find your 100 watt radio set for GMRS, well... BTW, for FRS there are only two actions, both related to misuse. One guy actually built an FRS repeater out of a GR1225. Presumably the receivers were not FRS accepted :-)

Yes, and no. You can reprogram the locations like any other radio. But, there are fixed functionalities that cannot be changed, and are not apparent in the CHIRP interface. Specifically: You can only transmit on locations 0 to 23 Only locations 16 to 22 have an offset for transmit, and that is fixed at +5mHz. So, if you want to be able to transmit simplex on all 15 GMRS frequencies and use all 8 repeater pairs, you must start in location 0. But, you can set location Names. So, you can "Name" location 0 as "GMRS 1" Again, CHIRP will let you set anything, but the radio will only do what it is preprogrammed for.

I may have misphrased that. What I meant was if a radio is FRS certified, then it cannot have a removable antenna. Period. Having dual certification, FRS & GMRS does not change that.

I thought in those cases, you could not legally the radio on both services at the same time -- you'd need to turn the radio off and then on again (while holding some button or knob) to change the mode. But, I'd be glad to be wrong. If there is a simultaneous part 90 & part 95(a, b or c) [and maybe the ham bands] radio out there could you post the make/model.

Missed this earlier. By definition NO radio certified for GMRS can be used on the ham bands as sold. Perhaps it could be modified, but that would void its GMRS certification. As for the reverse, any radio that can operate on the ham bands, which is pretty much anything built since spark gap ratios were retired, would be illegal to operate on GMRS. Simply because it could operate on non-GMRS frequencies. I am fairly confident there is no radio made that can legally operate on GMRS and any band other than FRS, and then only if the antenna cannot be removed.

Which would automatically disqualify GMRS certification.

Which, I believe, has been replaced by the DR-638T. If so, you can be sure it is not Type Accepted under any section of Part 95. One killer item is the ability to transmit outside the allocated channels. There are probably other issues as well. But, it doesn't matter.