BoxCar

Fixed stations don't connect to mobile stations.

Dimmy antennas are used to contact stations 200 miles away.

Any 50 ohm load rated for 50W or more.

Our ham club operates a GMRS repeater on our tower and is maintained through club resources. Yes, it is licensed through a club member holding both licenses. So, stating a club cannot operate and maintain a GMRS repeater is incorrect. The licensee is the owner of record and responsible to the FCC but it's a ham club operated repeater.

From SoCal? He only knocks what anyone has.

And to add, the tones used as default vary between manufacturers. Retevis tones are not the same as Baofeng's or TID's.

Stereo to mono plugs DO NOT combine two channels but keep them separate. Combining the two channels through wiring only affects the impedance seen by the amplifier and speaker. To work correctly, the two channels have to be fed into a mixer which combines the audio signals and keeps the impedance of the circuit constant. What the stereo to mono plugs go is combine the ground return path while putting one audio signal on the tip and the other to the ring.

Heliax is the best, but a lot depends on the repeater itself. How much power does the repeater have? What antenna are you planning to use? A low power repeater (less than 25W) can usually get by with LMR 400 or better coax for that length run. Coax loss can often be made up with antenna gain. Where the repeater is located, terrain, and intended use also factor into the need for Heliax over coax. Repeaters only cover the area from the antenna to the radio horizon and increased power only means the signal is stronger in the same area determined by the antenna type and placement.

Welcome!

I don't think any antenna would survive that kind of abuse. Think about a 1/4 wave stubby like a Laird or similar that's about 6" high. They're relatively inexpensive but work well.

Caca de toro - or BS to those not understanding Tex-Mex. You can't make such a wild assertion without empirical truth to back up your WAG. Hams in my area are actively reaching out to GMRS users to the point where they have collocated GMRS repeaters at their stations. The clubs I belong to are talking to GMRS users and preppers actively helping them make the best use of the equipment they have.

One is dyslexic.

I would check the antenna. Use a Nano VNA if possible and check the frequency the antenna resonates at along with the bandwidth. As you stated it's a home brew, its possible it is off frequency.

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@Jaay Because it's a contest -- and I'm winning!