GMRS Radio

What if a CB antenna and GMRS antenna were mounted next to each other on the same mount? And the antenna ran along roughly the same route? Would the proximity of the two antennas cause problems with each other compared to if they were mounted and ran in different areas?
Absolutely this would be a problem. Its like two women standing next to eachother having separate conversations with you. Will it work? Sure! EVERYTHING WORKS; some thing work better.

A local asked for help tuning a CB antenna he installed in the back of his Toyota. Against my suggestion he wanted to run a 3' Firestik. With an analyzer hooked up to his coax, I showed him how the SWR changed with me just walking closer to the antenna in the bed of the truck. The SWR was marginal with the 3' and trimming the coax would have been the next step. We swapped out the 3' for a 4' and the SWR came down as expected, without adjusting the coax length. The antenna is mounted right behind the cab and interfering with the antenna. Its a compromise he was willing to take. I was ready to drill a hole in the top of the 2021 Toyota...he wasn't.
 
The issue its that the GMRS antennas need ground plane, this small bases does not provide such a good ground plane so the CB antenna mounted besides becomes the ground plane but vertically affecting both antennas.
Sorry, this is completely wrong. A 1/2 wave GMRS antenna wouldn't need a ground plane. The "second half" of the antenna is the body of the vehicle and as long as the mount is properly "bonded" to the chassis its fine, but not ideal. The CB antenna does not become a ground plane at all. The antenna it self is insulated form ground/chassis. Its just another non-resonant element that interferes with the GMRS antenna due to proximity.
 
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Another question, does anyone have the MXT-275? If I understand the description correctly, the speaker is built into the mike. Is it clear and have good sound?

Im considering that one as well as the MXT-115.

My buddy has the -275 installed in his glove box. He is very happy with it. I have the -115 installed on my AAR over head. To me seeing them both they are both so similar in quality I don’t think you can go wrong with either one. I will say that I would give the -275 an extra point for having a speaker in the mic which seem nice if wanted.

I’ll be adding the -275 to my truck and doing a install similar to Plumber1.


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Made a mount to attach to my MORryde mount.
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Sorry, this is completely wrong. A 1/2 wave GMRS antenna wouldn't need a ground plane. The "second half" of the antenna is the body of the vehicle and as long as the mount is properly "bonded" to the chassis its fine, but not ideal. The CB antenna does not become a ground plane at all. The antenna it self is insulated form ground/chassis. Its just another non-resonant element that interferes with the GMRS antenna due to proximity.
:rolleyes:
 
My buddy has the -275 installed in his glove box. He is very happy with it. I have the -115 installed on my AAR over head. To me seeing them both they are both so similar in quality I don’t think you can go wrong with either one. I will say that I would give the -275 an extra point for having a speaker in the mic which seem nice if wanted.

I’ll be adding the -275 to my truck and doing a install similar to Plumber1.


View attachment 244878

Made a mount to attach to my MORryde mount.
View attachment 244879
I have an ARR mount too with a Uniden 520 on it. It looks like you have a 510 or 520 too. I was wondering if the -115 and 520 radios would fit on the ARR mount side-by-side and still be able to move the visors.

Are they in the way of your visors?

I would actually prefer the -115 rather that trying to see all the controls and display on the mic of the -275. I will say I do like how the -275 would take up less space by mounting the radio under the dash.
 
I have an ARR mount too with a Uniden 520 on it. It looks like you have a 510 or 520 too. I was wondering if the -115 and 520 radios would fit on the ARR mount side-by-side and still be able to move the visors.

Are they in the way of your visors?

I would actually prefer the -115 rather that trying to see all the controls and display on the mic of the -275. I will say I do like how the -275 would take up less space by mounting the radio under the dash.
Yes it’s a 520. Plenty of room side by side for the visors to move freely. I messed around the CB I’m top with GMRS on bottom and vice versa. I liked this way the best.

Sorry about the glare in this photo.
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I just took it to give you a better idea of the amount of room. I tipped the visors down a little. Hope it helps.

I think knowing where someone wants to helps with the decision on what model to get.
 
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The 115 and the 275 are basically the same radio sans the the display controls. The 275 has a usb charge port on the base unit which makes it nice to charge my HT while driving.
 
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Yes it’s a 520. Plenty of room side by side for the visors to move freely. I messed around the CB I’m top with GMRS on bottom and vice versa. I liked this way the best.

Sorry about the glare in this photo.
View attachment 244926
I just took it to give you a better idea of the amount of room. I tipped the visors down a little. Hope it helps.

I think knowing where someone wants to helps with the decision on what model to get.

That's great, thank you for the picture, it really helps. I had to use one of those elbows on my 520 also because of the plastic trim piece at the top of the windshield.

Man, I thought the 520 was small, but it look huge beside the -115. LOL

Does you 520 loosen up in it's mount? I've put new star washers on the twist knobs, tried rubber washers and eventually used a small velcro strap around the rear plug on the radio and through the footmans loop to keep it from eventually rotating until the controls are pointing up.
 
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@Dino - KX6D I bought some handheld Midland GMRS radios for the trip. Will they need to be programmed before I can communicate with y’all or will they work how they come out of the box?
 
That's great, thank you for the picture, it really helps. I had to use one of those elbows on my 520 also because of the plastic trim piece at the top of the windshield.

Man, I thought the 520 was small, but it look huge beside the -115. LOL

Does you 520 loosen up in it's mount? I've put new star washers on the twist knobs, tried rubber washers and eventually used a small velcro strap around the rear plug on the radio and through the footmans loop to keep it from eventually rotating until the controls are pointing up.
I was amazed on how small it was when I opened the box. When I put it above the -520 first I couldn’t even see it lol.

Yes mine also gets loose. Your Velcro trick is a good one. I did however trash the star washers and used some 8-32 split washers. Slightly better so far.
 
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@Dino - KX6D I bought some handheld Midland GMRS radios for the trip. Will they need to be programmed before I can communicate with y’all or will they work how they come out of the box?
You just need to set the DCS codes in your radio. Take a look in the manual and if you can't figure it out I or anyone else can help you input those. The GMRS radio frequencies are already programmed in your radio and it should have the capability to set the proper codes.
 
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I purchased two 1/2 wave GMRS antennas to experiment with. The thing with a 1/2 wave antenna is it doesn't require a ground plane you could drill a hole right through your fiberglass hard top and with the proper length cable, no ground plane would be necessary. This is accomplished with a matching network in the base of the antenna.If this antenna was a CB antenna it would be 18' tall! As we go UP in frequency, the antennas get smaller.

I placed it in various spots on the Jeep. Ideally I would want it high and away from any metal like roll bars, hoods, grills, window frames doors, etc. At the very least, as far away as possible. Here are a few ideas...

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My favorite would be a small rack over the spare tire or an extended mount that raises it up. Since it doesn't require a ground plane there are lots of options. You still want to stay away from other metal objects the best you can.
 
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I have my GMRS antenna right where @Dino - KX6D has his on the front outer corner of the driver's side fender. Lowest SWR of all the places I tried, about 1.3. Middle of the hood was 2.0 - although it should be a better location. YMMV...
 
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Can you elaborate on the wave factor? I have a 5/8 wave antenna that is supposedly no ground plane, I have read that no ground plane antennas perform better with a good ground plane? So, is a no ground plane antenna a compromise for us that have less than desired mounting location?
 
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