Ham (2m/70cm) + GMRS Antenna for the RV

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I am new to ham radio. I have the technician license and plan on staying at that level for a while. My main interest is using the ham while on the trails in my jeep.

GMRS is so heavily used, and has other benefits in the fact that all of my family can legally use the GMRS, since I have that license as well.

I have the mxt400 50watt GMRS radio in my jeep, and want to be able to use it in the RV while driving for convoy conversations.

Since my RV has the girard roof rails, I have to be concerned with overall height. Ideally I would mount it like I have placed my surecall or panorama cellular antennas.

The GMRS uses approx. 460-470Mhz range of the 70cm, so I assume that a dedicated GMRS antenna would be better.

For Ham, I would be using my HT, so I would want a 2m/70cm dual band.

There are so many antennas, I am hoping that a fellow RV /ham user has already found the antenna that would work for me.

I could make a 19" work, but that would place it on the endangered list for trees.

Obviously I am going to sacrifice distance. I don't plan on doing contests, so I am ok with an antenna that is going to be shorter range. As long as the SWR's are less than 2.5:1 in the operating frequencies, I would be happy.

Thanks for your input.
 
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Welcome to ham radio, @redbaron. I've been a ham since 1974.

I think you are going to find it challenging to mount an effective, wide-band antenna for 2M/70CM/GMRS on the roof. Nothing that I know of that meets your criteria and is 19" or less tall. Comet antennas makes a very good dual-band (2M/70CM) antenna that is able to cover the GMRS/FRS band with SWR under 2:1...but, it is 40" tall.

In general, a larger diameter antenna can be shorter and have a wider bandwidth, but I haven't found anything like that for the frequencies you are interested in. If I find one, I will let you know.

TJ
 
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Thanks @TJ&LadyDi . I have seen a few glass mount / pass thru type antennas, but my experience with those (CB & Cellular) has been less than ideal.

RedBaron73 (KI5IBV)
 

Jim

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There are so many antennas, I am hoping that a fellow RV /ham user has already found the antenna that would work for me.

There’s a ton of space to mount a radio up under the dash; it’s just a bear to work up under there. But pulling off the vanity inspection plate under the steering column provides plenty of easy access and made a great place to mount a radio. (That's my radio in the first second picture with the faceplate removed.)

I ran power wires from the battery, through the firewall hole, and over to the radio. I like a direct power feed so I can operate the radio without the engine running. I suppose the opportunity for a drained battery is there but this is the same setup I have on my YJ and it hasn't bitten me yet.

My radio is a Yaesu FT-8800 (Modified to opperate on GMRS and FRS) with a detachable face that can be mounted remotely. Having this option opens a world of places to mount the “controls” for the radio and I decided to install mine above the rearview mirror.

I fabbed up a metal brace and connected it to the detachable faceplate. Then with a couple of screws and some Velcro, I attached the faceplate just above the mirror.

For an antenna, I used a Diamond K4005-NMO lip mount with a Larsen mobile 2m/70cm antenna which works great with GMRS or FRS.

It took me the better part of the day to put this all together, but all-in-all, I’m happy with the results.
 

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Joined
Nov 3, 2019
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497
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2019
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Dutchstar 4369
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2013 Chevy Silverado 2500HD Crewcab / 2020 Jeep Wrangler Unlimited Rubicon
Thank @Jim , that looks like a great installation.

I am looking for something to put in my Dutchstar when I am not in the jeep. The jeep is easy to mount antennas, lots of space. The RV -- has plenty of space, but no easy place for an antenna.

I do have a question regarding the MARS/CAP mods to get access to the GMRS frequency.

For this conversation, lets not discuss the "legality" of this.

My question is in regard to performance. I have seen documentation that suggests that the outer edges of the 70cm, where the GMRS lives, will cause very high SWR and very low power compared to a dedicated rig.

Have you measured your SWR on the GMRS frequency?

Another question is how you are handling the privacy groups of GMRS. Are these normal CTCSS tones, or are they something unique?
 

Jim

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My question is in regard to performance. I have seen documentation that suggests that the outer edges of the 70cm, where the GMRS lives, will cause very high SWR and very low power compared to a dedicated rig.

Have you measured your SWR on the GMRS frequency?

Another question is how you are handling the privacy groups of GMRS. Are these normal CTCSS tones, or are they something unique?
For a while, I was using a Yaesu 8800 as a base station with a 2 Meter Diamond X300A, and I don’t remember any SWR issues, but I imagine your choice of antenna's will play into that. As for privacy groups, I just put all the radios (which are all 8800’s) on the same frequency and ignore any CTCSS or DCS codes.

Power seems to be between 35w and 50w, depending on what frequency, but of course I always turn that down to the legal watt’s out. The 8800 has a quick select button that allows for low/medium and high power and that's a nice feature.

I have a Yaesu 8800 in my Jeep, another one that is slated for the Phaeton, and another that I recently took out of my YJ when I was getting it ready to sell. I’ll probably use the extra in one of the other vehicles here on the spread.

I like the 8800 because it’s easy to program (I use RT Systems Software to program them) and with them all using the same hyper-memories, it’s easy to remember what each set of options does.

EDIT: BTW, I have several HF radios, but I'm seldom found on HF anymore. It was fun for about a month and I made a slew of long distance contacts, but I have more fun now hitting the repeaters in, and around, my area. I'm at 3,700' and can easly get into Atlanta, which is about 100 miles away. I find that to be much more fun that hoping that conditions are right for a QSO in another country. But to each his own, that's what makes radio fun!
 
Last edited:

Jim

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Spoke with a friend who has a glass-mount antenna for 440 and 2M on his motor home. He reports good gain with a low profile. He also warned that on a windown that has internal tinting, which many have now, the antenna is useless.
 
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Spoke with a friend who has a glass-mount antenna for 440 and 2M on his motor home. He reports good gain with a low profile. He also warned that on a windown that has internal tinting, which many have now, the antenna is useless.
Metallic tints are the ones that interfere with radio signals. A high quality 3M tint does not interfere with radio, they are made with tint containing ceramic material. 3M Automotive Window Films Product Simulator
 

Jim

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Joined
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2019
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Spoke with a friend who has a glass-mount antenna for 440 and 2M on his motor home. He reports good gain with a low profile. He also warned that on a windown that has internal tinting, which many have now, the antenna is useless.
Which antenna does he use? This may be the way to go.

2019 DSDP 4369 * Active Air * NHSO
 

Jim

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Which antenna does he use? This may be the way to go.

2019 DSDP 4369 * Active Air * NHSO
I went through our emails and here was his latest answer.
"For 2M and 440 I like the glass mount. Easy to mount and no holes to drill and works very well. Wal Mart has them on the web site but I am not real happy with WM right now and their no open carry policy, Home Depot carries them on the web site. And HRO."

I'll check with him on the exact name that he bought but I get the impression that just about any of them are OK. Pick the one with the most gain in the price range you're looking for, and of course the size that fits, and run with it.

But as I said, I'll email him now for the exact one he bought.
 

Jim

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Just an FYI. Home Depot, Walmart, and the others don't actually sell Ham Radio Antenna's in their stores. But you can get them on their Internet presence. I bought a Tram a few years ago, think I got it from Home Depot, and it turned out to be a super antenna. Rivals the Diamond at half the price, actually was 6' longer, more gain, and it's still hanging in the tree out back.
 

Jim

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I'll check with him on the exact name that he bought but I get the impression that just about any of them are OK.
@redbaron, heard from John and he said it's a "Tram 144/440 mhz pre tuned glass mount" He said he didn't see a model # on it. I've got a Tram for my base station and it works great. I would expect the same quality/performance from their mobile antenna's as well.
 
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I Plan to mount mine (ngp Diamond 5/8 wave) on the ladder and run the coax under the MH to the front somewhere. I never had as good performance through the glass as with outside antennas with coax directly connected. Remember, running mobile you will often be in compromised areas for both Tx & Rx.
 
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