GMRS yagi question

[brandon7861]

Just wanted to get some input about what people want in a GMRS yagi. I have been wanting to get into the yagi business for a while now and I am just getting around to building a prototype now that I have tower space to test it. This one is being made with crappy tools, the ones I sell will be much nicer looking once I get jigs on the drill press and a good saw set up, but the idea is to make them indestructible with heavy wall 3/4" tubing and solid 1/4" elements because they are small enough for the weight to not be a big concern (and birds have bent my other ones). Right now, the elements are hand knurled with a chisel and press fit in, but I plan to weld them in place on future builds.

I have 2 questions before I move forward:

• Would people prefer them to be 50Ω, or should I set the gamma for 75Ω and include RG6 connectors and a 75Ω to 50Ω matching network for the radio side? Low loss TV coax is cheap and can easily handle 50w (the GMRS limit) and would give people the opportunity to repurpose old satellite TV coax.
• Should I use regular SO-239's, SMA, or would users prefer the mini-UHF connectors like the Motorola radios use (if I can even find those ends for RG6 quad shield)? I know F-type won't handle 50w, otherwise I'd just use those.

Here's the ugly prototype I worked on today, haven't finished the gamma or welded on the coax connector bracket yet. Made this out of scraps I had with hand tools, so its a little scuffed up and not drilled perfect, but will be once I get the design complete and shop set up.

The sharpie I used to circle the center punch marks makes it look like I used too big of a drill bit lol

Edit: perhaps good quality F-types would work. 50w into 75Ω is only 817mA of current, and with any reasonable length of coax, it will be less.

 

[Shadetree Mechanic]

I would be interested in one, the option to use 75 ohm tv coax would be great. I have a big roll of it in the basement.

 

[Blackcat630]

Might also consider a N connector. N female is the standard on all my 222, 432 and up yagis..

 

[Rick330man]

Interesting.

GMRS has a loyal crowd down here in South Florida. The South Dade GMRS club and the Conch Auxiliary Radio Emergency Services (CARES) group have joined forces and set up a chain of GMRS repeaters that covers from Key West all the way into Palm Beach county.

Most of the repeaters use omni-directionals but Yagi's have seen service, too. In the Keys in particular, Yagis were fine for filling repeater gaps. They have been really good when run as a pair in phase with one pointing one direction and the other going a different direction. Also, guys out on boats have had good luck hitting the repeaters from way out in the ocean - especially with Yagis.

Bottom line: I see the need for both a 50 ohm and a 75 ohm version.

Good luck.

 

[Captain Kilowatt]

Bottom line: I see the need for both a 50 ohm and a 75 ohm version.

Good luck.

Why would you ever need two different impedances available in the same antenna? 75 ohm is used in television and that is about it. Any impedance issues due to phasing can be overcome with proper coaxial cable lines.

 

[brandon7861]

I may just get a big roll of heliax and send the desired length with the antennas. Those that want to do it right with low loss can pay to play, but maybe if I get the heliax in bulk, it will save the buyer at least a few bucks getting it through me instead of a separate order for a short run of it and having to buy a crimper for one job.

Unfortunately, I am currently going through a somewhat unexpected breakup and the antennas are on hold until I finish getting the household items cut in half and her stuff in storage.