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Antenna mount type and position


WRZT411

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I am looking at purchasing a mobile antenna to use for my GMRS HT in my truck.  Mobile radio will come later.  I don't want to drill thru my roof so that's not an option.  That leaves me with a fender or hood lip mount.  Could possibly do something on the fiberglass topper. 

I have read that anything other than center of mass on the roof will distort the signal. Thinking that as long as the tip is above the vehicle roofline then all should be good but I'm speaking out of an abundance of ignorance.

Any suggestions on mounts and high gain antennas much appreciated.

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Getting the antenna centered on the cab roof is always best. But lip mounts will work. Try to get as much of the antenna above the roof will help.

You can attach a steel plate to the top of you camper shell and use a mag mount. I've done that with the aluminum tool box on my SxS and the mag mount stays put.

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I've had good luck with a lip mount and a Rugged Radios Point 5 antenna on the liftgate of my Sienna. Since the Point 5 antenna is a half-wave design, it doesn't rely on a ground plane, so getting it in the center of the roof isn't a big concern. Although some say it will do better with a ground plane, one of its reasons for existing at all is that it can work on a vehicle where there is no practical way to mount it on a metal surface. You may want to search for "No Ground-Plane" antennas if you want more options.

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Only 100% symetrical ground planes don't cause propagation distortion. Don't worry that much about it.   In my experience using field strength meters, mounting an antenna on a corner of a vehicle does cause the signal to be stronger across the vehicle to the opposite corner and 180° diagonally behind the vehicle.   Dead center front or back sends the strongest signal in those directions, but it's only a few db.  Any advantage or disadvantage would only come while the vehicle was stopped and you are making fringe contacts. 

Ability to mount the antenna higher will be more helpful than where on the vehicle. 

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Unless you are trying to bounce your signal off the moon, just mount your antenna in the best spot you can, as high as you can get it, and it will work fine for for highway/trail comms.

My antenna is mounted above the rear tail-light/rear fender of my jeep, below the roofline, where many "experts" warned me it "will not work". and while it certainly does not work as well as it could, it works just fine. I can hit a repeater with it at 92 miles and regularly get 20+ miles on simplex and have never had issues on the trail where i could not hear someone that others could, or they could not hear me.

My two words of advice are:

1) ignore the 'experts'

B ) - dont over-think it.

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42 minutes ago, OffRoaderX said:

Unless you are trying to bounce your signal off the moon, just mount your antenna in the best spot you can, as high as you can get it, and it will work fine for for highway/trail comms.

My antenna is mounted above the rear tail-light/rear fender of my jeep, below the roofline, where many "experts" warned me it "will not work". and while it certainly does not work as well as it could, it works just fine. I can hit a repeater with it at 92 miles and regularly get 20+ miles on simplex and have never had issues on the trail where i could not hear someone that others could, or they could not hear me.

My two words of advice are:

1) ignore the 'experts'

B ) - dont over-think it.

Sounds like a decent antenna rig, mind sharing the model of it?

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I plan to install a Midland mobile in my son’s Jeep JK and recently found this Jeep owner who installed a Larsen pick antenna to the metal speaker bar overhead. It apparently has no issues with hard or soft tops and should perform similar to the Midland “ghost” 3db antenna. We like that it’ll be an easy install and hidden.

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Those work well for repeaters and car-car stuff. Not great for far away stuff. I run the Laird "pepper" shaker in my JT in the same spot under the soft top. Asreference the Midland will fit under the soft top with much room to spare. I jsut run laird as its a LMR grade antenna

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Those work well for repeaters and car-car stuff. Not great for far away stuff. I run the Laird "pepper" shaker in my JT in the same spot under the soft top. Asreference the Midland will fit under the soft top with much room to spare. I jsut run laird as its a LMR grade antenna

Thanks for the info. I run the similar Midland “Ghost” on the roof of my 4Runner with great results in the mountainous PNW. I’m hitting the repeaters well.

The antennas you and I have will work with his soft top, but not the hard top, which is why the puck. Mostly it’ll be car to car and repeater use for us too.

I’m considering pulling my MIdland 575 out of the Toyota and installing the Wouxun 1000 plus unit, then putting the Midland in the Jeep.

We shall see how it all works out.
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Thx all for the responses.  Looks like the Midland MXTA26 may be the one for me.  With a fender mount, it'll be about 6 inches above the roof line and a super easy install and cable run.

I only need about 5 feet of cable.  Are shorter cable available or would I have to chop whatever I buy?

Also, is there a real difference between a 5/8 and a 1/2 wave antenna?

 

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1 hour ago, WRZT411 said:

Thx all for the responses.  Looks like the Midland MXTA26 may be the one for me.  With a fender mount, it'll be about 6 inches above the roof line and a super easy install and cable run.

I only need about 5 feet of cable.  Are shorter cable available or would I have to chop whatever I buy?

Also, is there a real difference between a 5/8 and a 1/2 wave antenna?

 

The MXTA26 is an excellent performing antenna for GMRS. Do you intend to purchase a NMO mount and cable from Midland or another brand like Laird from a supplier like Arcadian Antenna? 

Midland has both a standard NMO mount and cable and a NMO lip-mount and cable. Either one will get the job done.

I believe for simplicity and convenience Midland installs the PL259 connector on the cable which is approximately 17 feet in length? In that case, you will have to whack off the connector and reinstall a new connector. Don't go cheap with a POS Chinese connector from Amazon. If you want it to work properly, buy a quality connector, like Amphenol, from a supplier like DX Engineering.

It would be easier to just tuck the excess cable under the carpet/mat or into an interior trim panel than whack off the connector if you are not comfortable with crimping/soldering on a new connector.

You mentioned that your fenders mount antenna will stick about 6 inches above the roofline. What make and model Truck do you have? 

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1 minute ago, nokones said:

It would be easier to just tuck the excess cable under the carpet/mat or into an interior trim panel than whack off the connector if you are not comfortable with crimping/soldering on a new connector.

and for deconfuckulation: You will experience zero noticeable degradation in performance if you roll-up the extra few feet of cable and tuck it away somewhere, vs shortening it, in-despite of what "some people" will try to tell you.

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To the OP.  There is the Ditch Light mounting option.  I found this to be great for GMRS one side and a CB on the other (yeah, CB for when on "The 5."}

I'm running an 8 watt handheld to that ~ 3db GMRS tuned antenna ($11), low SWR and hitting the local repeaters.  

Your bigger issue, when its all said and done will be the coax routing and how you go through the firewall, if going that route.  I went full in with a clutch delete plate (drilled it out) with an inserted boot for both coax and several two-pair of extra future use wires.

As for the extra couple of feet of coax on that side, that is all shoved in a BALL of WIRE  up under the dash right where the truck thieves will be trying to find my OBD plug...................... (gone).


 

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On 4/2/2024 at 7:05 PM, AdmiralCochrane said:

Only 100% symetrical ground planes don't cause propagation distortion. Don't worry that much about it.   In my experience using field strength meters, mounting an antenna on a corner of a vehicle does cause the signal to be stronger across the vehicle to the opposite corner and 180° diagonally behind the vehicle.   Dead center front or back sends the strongest signal in those directions, but it's only a few db.  Any advantage or disadvantage would only come while the vehicle was stopped and you are making fringe contacts. 

Ability to mount the antenna higher will be more helpful than where on the vehicle. 

I agree completely. 

It's also important to keep the electrical distance from the base of the antenna to the true ground plane as short as possible. I've seen antenna mounts where there are inches, as in 1-3 inches, from the base of the antenna to the metal body of the vehicle. Bad bad bad. Keep in mind that at GMRS freq 3 inches is 1/8 wavelength, and that's plenty to totally mess up the ground current phase compared to the radiating whip and cause the radiation pattern to go well above the horizon, read into space. In a city urban environments with lots of scattering off of buildings that might be OK, but in rural areas you definitely want as low angle radiation as you can get. Keep the base of the antenna right on the metal of the vehicle if you can. 

Hope this helps :)

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On 4/5/2024 at 11:33 AM, WRZT411 said:

Also, is there a real difference between a 5/8 and a 1/2 wave antenna?

If you don't have a GOOD ground plane for a 5/8 wave antenna, they really need it, don't waste your money on one.

If it's a true 1/2 wave they don't need a ground plane so you can mount them just about anywhere so long as you keep it away from nearby vertical metal supports, like roof pillars.

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47 minutes ago, Lscott said:

If you don't have a GOOD ground plane for a 5/8 wave antenna, they really need it, don't waste your money on one.

If it's a true 1/2 wave they don't need a ground plane so you can mount them just about anywhere so long as you keep it away from nearby vertical metal supports, like roof pillars.

Slight clarification: Agree with the 5/8 wave needing a good ground plane. And yes strictly speaking the 1/2 wave end fed does not need a ground plane at all. But....what does need a "counterpoise" frequently is the matching from 50 ohms to high impedance in order to end feed the 1/2 wave. If that matching is done with discrete components (caps and inductors) then no counterpoise is needed. If on the other hand the matching is done via a physical structure that radiates, ie: helical 1/4 wave is common and easy, then THAT needs some counterpoise to do-it's-thing. Probably does not have to be large, but should not be zero. 

Not sure why you would rule out roof pillars though???

 

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24 minutes ago, WRUW493 said:

Not sure why you would rule out roof pillars though???

They are going to be close to the antenna and in what is known as the "near field" so it couples into the driven element. That can booger up the impedance match, SWR issues, and the radiation pattern. It's not a guarantee you'll have problems but keeping the antenna away from from structures like that will at least avoid the potential for them. You read through the past comments over time here and you'll see this mentioned from various people.

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