GMRS antenna recomendations

[whitenoise]

This will vary person to person depending on the terrain/environment they were in when using the radio.

Thanks, that is obvious. I hope someone can indicate the conditions under which they're seeing a specific number. I'm coming from CB with the hopes of a big improvement, but it would be nice to get some real world data - on a good day we could talk 3/4 of a mile in line of sight conditions with the CB.

 

[Sand1235]

This will blow the CB away. Much clearer, much more distance. I doubt you regret it. My family and group of friends switched to these from CB's. No regrets and no going back.

Thanks, that is obvious. I hope someone can indicate the conditions under which they're seeing a specific number. I'm coming from CB with the hopes of a big improvement, but it would be nice to get some real world data - on a good day we could talk 3/4 of a mile in line of sight conditions with the CB.

 

[cody_roberts]

I'm using a Comet CA-2X4SR w/Spring on my adventure trailer GMRS Repeater and APRS Radio, I plan on getting another one for my tow vehicle w/a Kenwood D710G modified to reach GMRS frequencies.. just trying to decide if I should drill a hole through the roof and get it done or wait a bit longer and save up and put a front runner roof rack on and mount it to that.

I've been very happy with its performance, when I was setting up the 2m radio I noticed I was getting better reception in the driveway than my home station's J-Pole.. so I went out and bought a new base station antenna for home and my performance skyrocketed.

Folding antenna was pretty much mandatory for my trailer since the top of the antenna is ~13ft high now.. first antenna I put up broke clean off within the first few trips.. Ive since bent a spring on the Comet but the antenna held up fine, cheaper to replace the spring than the whole antenna.. but now I'm moving it from the passanger side to the drivers side right next to the ladder, so its further away from trees, I'll be able to see it in rear view mirror and folding it over when needed will be a quick 30s job without actually requiring stepping foot on the roof.

I didn't think the roof rack would be a good spot. I hope I'm wrong , I have a front runner roof rack and would love to throw my antennas up there.

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[prerunner1982]

There is more than enough metal to act as a ground plane for UHF, signal may be a little wonky if you mounted it to the cross brace as the main metal under the antenna is off to each side rather than in all directions but it should work.

 

[cody_roberts]

There is more than enough metal to act as a ground plane for UHF, signal may be a little wonky if you mounted it to the cross brace as the main metal under the antenna is off to each side rather than in all directions but it should work.

I was going to do fender mount , would this be better for uhf/vhf?

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[dreadlocks]

depends, if your using a basic 1/4 wave antenna.. you get unity gain and a high radiation angle so mounting it up higher or on fender wont really matter.. a 1/2 wave or 5/8 wave will get actual gain and more likely to reach to horizons (which is further away with more height), so with a bigger/flatter ground plane and would do better on roof or roof racks if they are properly grounded.. you still have the vehicle roof an inch or so below that is going to do alot of the work... a 1/4 wave is good in mountain terrain with mountain top repeaters above yeh and lots of elevation variances, in flat land a 1/2 or 5/8 will perform better.. many keep both on hand and change out as required, and also providing a backup spare.

fender would be best spot if you do forest trails on a Jeep, you can see an see an incoming impact.. reach out and lift the branch out of the way, cut it off or fold/remove antenna before damaging it.. dont matter where a broken antenna is mounted, its still broken.

 

[cody_roberts]

depends, if your using a basic 1/4 wave antenna.. you get unity gain and a high radiation angle so mounting it up higher or on fender wont really matter.. a 1/2 wave or 5/8 wave will get better gain and more likely to reach to horizons (which is further away with more height), so with a bigger/flatter ground plane and would do better on roof or roof racks if they are properly grounded.. you still have the vehicle roof an inch or so below that is going to do alot of the work... a 1/4 wave is good in mountain terrain with mountain top repeaters above yeh and lots of elevation variances, in flat land a 1/2 or 5/8 will perform better.. many keep both on hand and change out as required, and also providing a backup spare.

fender would be best spot if you do forest trails on a Jeep, you can see an see an incoming impact.. reach out and lift the branch out of the way, cut it off or fold/remove antenna before damaging it..

I do a lot of Forrest trails , wondering if limb risers will cause me any issues.

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[prerunner1982]

I was going to do fender mount , would this be better for uhf/vhf?

In line of sight communication height is always king.
Fender mount will work, just not as well as it could up top. I switched vehicles and went from a roof mounted antenna to a fender mount and definitely noticed a difference in receive and transmit. Not only due to height but also likely due to the ground plane being on only one side of the antenna.

For GMRS even a 5/8 wave antenna is only about 16", 1/4 wave is about 6". I have had 1/2 wave (≈40") and 5/8 wave (≈50") 2m antennas on the roof of my Jeeps not to mention a 102" whip and smacked them on trees daily for the last 5 years and never broken one. If you are scrapping trees low enough to break off a 6" or even a 16" antenna you are probably going to loose the RTT.

 

[DaveInDenver]

In line of sight communication height is always king.
Fender mount will work, just not as well as it could up top. I switched vehicles and went from a roof mounted antenna to a fender mount and definitely noticed a difference in receive and transmit. Not only due to height but also likely due to the ground plane being on only one side of the antenna.

For GMRS even a 5/8 wave antenna is only about 16", 1/4 wave is about 6". I have had 1/2 wave (≈40") and 5/8 wave (≈50") 2m antennas on the roof of my Jeeps not to mention a 102" whip and smacked them on trees daily for the last 5 years and never broken one. If you are scrapping trees low enough to break off a 6" or even a 16" antenna you are probably going to loose the RTT.

All spot-on. One thing I'll add, though, is you sometimes have to be aware of construction. A 1/4λ antenna naturally matches the coax and radio impedance and as a result needs only to be physically in contact. So mechanically they are usually very simple. A 1/2λ will need a matching network built in the base for impedance transformation, so are mechanically more complex. Same to some extent with 5/8λ.

The reason I mention this is if you look at the bases on the different antennas you'll some are more suitable for roof mounting.

For example, in this photo taken from Google, you'll see the Larsen NMO 2/70 in front. I run that antenna at the base of my windshield but as a roof antenna it's got some drawbacks. The base in a few inches tall and the whip can only flex so much, so you have to be aware that you need about a foot more than your roof height for clearance to prevent you from breaking the base or stripping the antenna off the roof.



Compare that to the Flexiwhip and Larsen 1/4λ whips that I had on my old truck. In this case it's only an inch or two of clearance necessary and even if I did happen to scrape they were so close to the roof that they were very unlikely to catch anything.



So I never felt I needed springs on this whips (especially the Flexiwhip, which is tough to hurt). But for a 2/70 I would consider a shock spring at least.

 

[cody_roberts]

My plan was to go with the Larsen 2/70 on an NMO fender mount left side. I like the roof rack idea , and still open to trying but I think clearance would prove to be an issue. At current height I'm right at 8 ft to the top of my tent.

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[prerunner1982]

Dual band (1/2 wave on 2m) on the front fender for voice, 5/8 wave on right rear corner for APRS, and 102" whip with adjustable loading coil (really more like 110"+) on left rear for HF.
I am switching back to my older XJ and the dual band will move back to the roof as well and may be replaced with another 5/8 wave.

 

[Ray_G]

Thanks, that is obvious. I hope someone can indicate the conditions under which they're seeing a specific number. I'm coming from CB with the hopes of a big improvement, but it would be nice to get some real world data - on a good day we could talk 3/4 of a mile in line of sight conditions with the CB.

So with a small antenna on my MXT-115 (same power as the 275-which is now what the truck runs), I can talk LOS for several miles with a like radio.
Several meaning at least 10; but those are unique LOS conditions where my buddy is on one ridgeline and I'm running up the other side of the valley on the highway talking back to him just to test it.

Day in/day out, in mountainous terrain with trees we are getting prob 2mi fairly consistently. More driven by LOS than anything else.

Long and short of it, you won't be dissappointed by the switch away from CB at all.

 

[DaveInDenver]

Dual band (1/2 wave on 2m) on the front fender for voice, 5/8 wave on right rear corner for APRS, and 102" whip with adjustable loading coil (really more like 110"+) on left rear for HF.
I am switching back to my older XJ and the dual band will move back to the roof as well and may be replaced with another 5/8 wave.

Very similar here. Larsen NMO 2/70 at base of windshield on left side, Larsen NMO 150 for APRS at base of windshield on right side. CB is currently a 5/8λ base-loaded whip on the bull bar. No HF mobile.

 

[Campndad]

I mounted a small browning for daily use and can switch it to the higher gain midland antenna on highway trips.
So far it works well.

Here is the long antenna.
Sadly it’s a little bent in several views that happened in shipping.

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[Billoftt]

Here is a good 5/8 wave antenna, 5.15 dbi gain. Pulse-Larson makes some really good quality stuff.
https://www.hamradio.com/detail.cfm?pid=H0-009385
Spec Sheet: https://pulselarsenantennas.com/product/nmo4503cs-2/

They make magnetic mounts out there with NMO connectors, but most of them have RG-58 cable. I highly recommend a traditional "through the roof" NMO with RG-8X cable or at least try to find a mag mount with RG-8X cable. GMRS is UHF and it will lose a lot more signal with RG-58 than with RG-8X. It is almost criminal that they include RG-174 with that 1/4 wave antenna with the kit. If you calculate the loss from the cable and the gain from the antenna, the 15 watts end up with 9.9 watts of Effective Radiated Power (ERP).