RoadApple

You did nothing wrong. Someone was just trying to bamboozle you. Ignore them. Remember - GMRS shares frequencies with unlicensed FRS where, for all practical purposes, there are no rules, protocols or norms and people will say or claim just about anything. Not that all GMRS users are well behaved either...

I'm glad you were able to get your radio programmed! It would seem silly to not allow tones to be assigned to any and all channels on a GMRS radio as some folk use tones (so call "privacy" codes) to filter out noise on simplex in addition to activating repeaters. I've yet to encounter a "fully locked down" radio, but I guess they are out there.....

Hey Nokones, Thanks for the general heads up about dual band antennas. My dual band seems to be an okay compromise for 2m/70cm although the SWR is notably better on 2m than 70cm. I actually have 3 different antennas I can swap in/out as needed depending upon what I'm doing at the time. While SWR is certainly not the only measure of performance, on GMRS, the antenna that gives me the best SWR (1.0 @ 462Mhz & 1.12 @ 467Mhz) is this tiny little low profile 6" quarter wave Tram 1126-B. It works surprisingly well, and I love that most people don't even notice that it is up there....

It took a while, but after looking at a variety of other options, I finally decided to get that 3rd brake light antenna mount purchased and installed. It was a little expensive, but it is working very well and I'm pretty happy with it so far! The pics below show it with a dual band 2m/70cm antenna. I've also used it simplex on GMRS with a very small Tram antenna with good results. Thanks again to all who provided constructive feedback on the topic!

Oh... that explains why HT's work better for us fat people! Especially on lower frequencies. Sent from my SM-S916U using Tapatalk

Really ?? I did not infer that "Code Talker" is mentioned anywhere in the FCC rules. I'm merely using that as an example to point out that "Plain Language" is an ambiguous term, not all foreign languages are commonly understood, and that perhaps the FCC's definition is not as clear or definitive as it should be!

___ @JHENRY, yours was a very good question. I'm fairly new to this forum, but I'm quickly learning to just ignore the regular trolls...

Just like the word "unreasonable" is arguably the most important word in the 4th amendment of the U.S. constitution, the definition of the term "Plain Language" is the key phrase in the FCC rules. Actually, the precise definition wording of section 95.303 as shown above poses a very interesting question as it is being presumed that all foreign languages, by definition, are not considered coded or secretive. It says: "Foreign languages and commonly known radio operating words...". It does not say; "Common Foreign languages and ..." The public at large cannot be expected to understand the wide variety of foreign languages that may be broadcast over the air. Clearly some recognized foreign languages are not at all well-known and in fact our own military has used this strategy expressly to create "secret communications"! "CODE TALKER" Wikipedia: "A code talker was a person employed by the military during wartime to use a little-known language as a means of secret communication. The term is most often used for United States service members during the World Wars who used their knowledge of Native American languages as a basis to transmit coded messages." As @UncleYoda pointed out, it is the FCC's responsibility to make the rules clear. At this point, I'm not sure they really are.

Great information... Glad to hear that it is working well for you. THANKS!

Good advice. Thanks for that!

Thanks for that input! For occasional 2m/70cm I use a very good local linked repeater network without any problems. For GMRS, I use mostly short distance simplex when travelling with a group or at the lake or other destination. The performance from my current mag mount which I usually place on the cab directly in front of the 3rd taillight, (basically where the antenna would be if I use one of these 3rd taillight mounts) works just fine! I like that location (up and centered) because it keeps the antenna up and out of the way of getting things in/out of the truck bed and I don't have to stare at it while driving. All the discussion about the effectiveness of the ground plane, while interesting, and not at all irrelevant, is just not too significant of a factor for my purposes. That's why my OP was a question more about the antenna mount itself (water leaks, strength etc.) and less about the RF propagation characteristics associated with its location which seems to be the direction the thread drifted. I'm not going to drill into my roof and I'm sort of tired of taking the mag mount on and off, so without any specific feedback that indicates that this type of mount is structurally problematic to my vehicle, l will probably give one of these mounts a try and hope for the best.

Exactly! I believe I only received 2 posts from people who have actually used that specific type of mounting device and provided some feedback about them. Nobody actually addressed my original questions, which were "Does it leak?" and "Are they strong?". The other posts that provided alternative mounting solutions, alternate recommendations or general antenna considerations regarding ground plane etc. were all valuable answers or comments to different questions that I did not specifically ask. I am still appreciative and thanked those people for their contributions to the topic. Looking at my OP I did not ask "what is the best way to mount an antenna?" Sorry if my communications sounded dismissive of others effort to help as that was not my intention.

@WSEZ864 Thanks for the suggestion about the back rack, and for the photo! Very helpful. That is certainly an interesting option worthy of consideration. @WRUU653 Thanks for the A-Pillar suggestion. I do understand compromises... Cost isn't a primary consideration for me, but even so the 3rd tail-light mount is in itself sort of a compromise, rather than following the recommendation of the "drill-baby-drill" enthusiasts who advocate for just installing that NMO mount. While an NMO mount installed dead center of the roof of my truck cab might be the best solution for RF purposes, that isn't necessarily the best solution for my purposes. I've been browsing YouTube videos about removing the headliner as was suggested by @WRUE951 and unless you are someone who does that sort of thing all the time, it appears like it could potentially be a PITA that is not without its own considerations and complications. In the process, I've also stumbled across a great many videos regarding replacing or fixing a 3rd taillight on these trucks. Some replace it for the purpose of a cargo/5th wheel bed camera, others for brighter or flashing LED lights etc. Many people with many different reasons. However, there are also folks that speak of damaged headliners as a result of leaks from a worn 3rd taillight lens gasket. Many suggest that it is not "IF" it will eventually leak, but rather "WHEN" it will leak, and they advocate replacing the gasket and resealing these 3rd taillight assemblies with silicone as a preventative measure. Something to think about... Interestingly enough that gets me back to my original post about this type of antenna mount where I asked those with direct experience using these devices: "Do they leak?" I'm thinking of an antenna being pushed by wind or by hitting trees, etc. and wonder how that might contribute to breaking or otherwise compromising that watertight seal around the mount? IOW, if these 3rd taillight assemblies are prone to leaking, maybe introducing an antenna mount there would be inclined to make matters worse. Absolutely nothing is without compromise!! Again, thanks for the comments and feedback on the topic.

@WRYZ926 Great information here. Thanks!! I was aware that the different ground plane clearances of the various conductive sections of my truck (Hood, Cab & Bed) would alter the reflective properties of the RF counterpoise. I was not aware that the vertical distance between the antenna on the cab and my truck bed, although more than a wavelength at GMRS frequencies, would effectively nullify all effectiveness of my truck bed as a ground plane!! I'll certainly need to research and read up on that... My current magnet mount has been placed very near the 3rd tail-light location and suffers from the same ground plane issues and so far the performance has been acceptable to me. I currently use a 5/8 wave GMRS antenna (although I'm not married to it - on rare occasions I swap it out for my 2M/70cm antenna) and at GMRS frequencies only about 15" of surface area is needed for an effective ground plane. So, if RF optimization were my ONLY consideration, shifting that GMRS antenna forward a few inches from the rear of the cab would probably be close to as good as it is going to get for my vehicle... Many of the comments thus far suggest just biting the bullet and drilling that 5/8" hole in the roof of the cab of my truck and installing an NMO mount as the best approach. I really do appreciate the feedback and comments! But OUCH... I just have a real aversion to that, and most likely will never do so and would rather just live with a magnet mount. Perhaps I should have mentioned in my OP that my truck has a retracting moon roof which significantly complicates things as far as drilling and mounting anything in the roof of the cab more than a few inches forward of that 3rd tail-light because of the sliding glass, retraction motor, etc. of the moon roof inside the roof of the cab. And yes, the moon roof glass too impacts my ground plane to some degree. If it's not one thing, it's another... But still I'm seeking the convenience of some kind of permanent mount, even if not optimal from an RF perspective, which as stated in the OP, is why I'm looking at whatever alternate mounting solutions I can find. Hood/fender mounts are often a no-drill option but those too often force you to route the coax thru an RF noisy engine compartment. They also tend to force you to mount them on either the right or left side of the vehicle which alters the radiating pattern to the sides, not to mention that you usually end up with the antenna being lower than the cab of the truck thus causing a certain amount of unwanted RF reflection if not some signal blockage. I conceded that there is no perfect solution, and things are never as simple as they may sound. So, while I'm not yet SOLD on this 3rd tail-light mount, and it is very expensive, thus far it seems to be a path to solve my specific problem. This is why I'm looking for folks with first-hand experience specifically with these 3rd tail-light types of mounts, even though any and all feedback is much appreciated! Thanks again...

@WRUE951 Thanks for sharing your experience. I hear you. I'm not thrilled about pulling the headliner either, as those things always turn out to be more difficult than we anticipate, but I figured that if I drilled a hole for a mount in the roof of the cab, I'd be going down that path anyway. I agree the price is very steep for an antenna mount! For my make/model/year truck the mount is no bargain @ $360 but if it avoids the potential for water leaks that can occur when you drill holes in the roof, (I've seen a lot of that with fleet vehicles) it is, from my perspective, worth the price. Also, I'll be sure to check Ebay "IF" I end up going with this type of solution. @Socalgmrs Thanks for your comment. On my 2018 GMC Sierra pickup truck (w/ a 6' truck bed) the 3rd brake light is very close to being as centered, front-to-back and right-to-left, as you can get. Thus, I don't believe this location sacrifices 180 degrees of ground plane as you suggest. I'm not wanting to direct the radiating pattern in any specific direction. If I'm not understanding your comment here, please explain... Thanks