Dual band antenna & location for jeep wrangler?

[secretspy711]

Trying to decide on the best antenna and mounting location for my situation and looking for advice.

I have a Jeep Wrangler JKU, hard top with a Maximus-3 roof-rack. (It's not the typical roof rack you see on jeeps that have bars extending down to the tub on each corner of the jeep -- this one is a platform that sits on brackets that penetrate the hard top and is supported structurally by the roll bar inside.) Eventually I will mount 2 of whatever antenna I choose... 1 for voice and 1 for APRS.

Also of significance is that I'm in Colorado, and there are repeaters on mountain-tops, so a long antenna may not be necessary.

The best location for RF-performance would obviously be right in the middle of the roof rack. (I may need to improve the grounding of the rack itself for this to work.) The problem is that I also like to park in a garage and there's only about 4-5 inches between the roof rack and the garage opening. And if I'm mounting 2 of them, they would probably end up on opposite corners, or 1 on each front corner.

I don't *think* I want a manual foldover antenna, mainly because I've been using my radio around town, and I don't want to have to get out of the jeep to fold the antenna down every time I come home. But maybe after the novelty wears off then I might find myself only using it for trail runs and not for "everyday" use... I don't know. It's not looking that way though.

Option 1 is the Diamond K9000 motorized mount. Neat, but a little pricey @ $100.

Option 2 is to get a somewhat short, but rugged & flexible antenna and just let it smack into things. On my list are:
Comet SS-460SB
Comet SSB-1
Diamond AZ504SP
Larsen NMO-2/70SH
All of those antennas are between 15 and 19 inches tall, and are flexible or include a spring near the base. These will smack the garage but won't be so tall that it would be a nuisance.

Option 3 is to get a taller antenna like a Larsen NMO-2/70B (34.75" tall) and mount it on the cowl / fender. I'm pretty sure I can mount it there and still fit in the garage. It would be similar to my AM/FM antenna, except mounted on the driver's side. My worry here is that the metal A-pillar and roof-rack will block much of the radiation pattern. Is a longer antenna mounted lower better than a shorter antenna mounted higher?

 

[KK4JUG]

I'm not familiar with any of the antennae that you mentioned. I'll leave that to the experts.

But, scratch #3. Too much RF entering the vehicle. In a couple of months, you'll start to glow.

 

[fyrfyter33]

Trying to decide on the best antenna and mounting location for my situation and looking for advice.



I have a Jeep Wrangler JKU, hard top with a Maximus-3 roof-rack. (It's not the typical roof rack you see on jeeps that have bars extending down to the tub on each corner of the jeep -- this one is a platform that sits on brackets that penetrate the hard top and is supported structurally by the roll bar inside.) Eventually I will mount 2 of whatever antenna I choose... 1 for voice and 1 for APRS.



Also of significance is that I'm in Colorado, and there are repeaters on mountain-tops, so a long antenna may not be necessary.



The best location for RF-performance would obviously be right in the middle of the roof rack. (I may need to improve the grounding of the rack itself for this to work.) The problem is that I also like to park in a garage and there's only about 4-5 inches between the roof rack and the garage opening. And if I'm mounting 2 of them, they would probably end up on opposite corners, or 1 on each front corner.



I don't *think* I want a manual foldover antenna, mainly because I've been using my radio around town, and I don't want to have to get out of the jeep to fold the antenna down every time I come home. But maybe after the novelty wears off then I might find myself only using it for trail runs and not for "everyday" use... I don't know. It's not looking that way though.



Option 1 is the Diamond K9000 motorized mount. Neat, but a little pricey @ $100.



Option 2 is to get a somewhat short, but rugged & flexible antenna and just let it smack into things. On my list are:

Comet SS-460SB

Comet SSB-1

Diamond AZ504SP

Larsen NMO-2/70SH

All of those antennas are between 15 and 19 inches tall, and are flexible or include a spring near the base. These will smack the garage but won't be so tall that it would be a nuisance.



Option 3 is to get a taller antenna like a Larsen NMO-2/70B (34.75" tall) and mount it on the cowl / fender. I'm pretty sure I can mount it there and still fit in the garage. It would be similar to my AM/FM antenna, except mounted on the driver's side. My worry here is that the metal A-pillar and roof-rack will block much of the radiation pattern. Is a longer antenna mounted lower better than a shorter antenna mounted higher?

As long as the tip clears the roof, you’re fine. That’s the part that’s most important.

Traditionally, longer antennas have more gain than shorter ones, so they are better.

Did you consider a spare tire antenna mount? Like this: https://www.quadratec.com/products/...DxkdscYLEfeRlOtkrbSTgxUpXUbGIR3kaAh_IEALw_wcB

 

[secretspy711]

I'm not familiar with any of the antennae that you mentioned. I'll leave that to the experts.

But, scratch #3. Too much RF entering the vehicle. In a couple of months, you'll start to glow.

Interesting you say that. The #3 (on the cowl/fender) is often said by jeepers to be the #1 best place to put an antenna (assuming in the middle of the hood is a no-go). I'm not sure I believe the exposure limits anyway since it's non-ionizing radiation.

 

[fyrfyter33]

Interesting you say that. The #3 (on the cowl/fender) is often said by jeepers to be the #1 best place to put an antenna (assuming in the middle of the hood is a no-go). I'm not sure I believe the exposure limits anyway since it's non-ionizing radiation.

Also remember your vehicle is like a giant faraday cage. The amount of RF actually getting in using such a setup is limited. It’s the same reasons internal antennas have issues.

 

[secretspy711]

As long as the tip clears the roof, you’re fine. That’s the part that’s most important.

Traditionally, longer antennas have more gain than shorter ones, so they are better.

Did you consider a spare tire antenna mount? Like this: https://www.quadratec.com/products/...DxkdscYLEfeRlOtkrbSTgxUpXUbGIR3kaAh_IEALw_wcB

Yes, actually I have my CB antenna back there already, and there's an open hole I could use for the ham antenna, but there are 2 things wrong with it... 1, it's between the tailgate and spare tire, so RF can't "get out" very well, at least not from the base of the antenna. 2, won't the CB antenna being next to it severely affect the tuning?

I was actually thinking of moving my CB antenna to get longer range. But it works fine for trail rides.

 

[secretspy711]

Also remember your vehicle is like a giant faraday cage. The amount of RF actually getting in using such a setup is limited. It’s the same reasons internal antennas have issues.

Yes, but not as much of a faraday cage as a "normal" vehicle with a steel unibody. The jeep jas a fiberglass roof. I've just put an aluminum platform on the rear half of it.

 

[cmdrwill]

snip

But, scratch #3. Too much RF entering the vehicle. In a couple of months, you'll start to glow.

Yes, that would exceed the RF Radiation Limits set forth in the FCC rules. If you keep your transmitter power at 7 watts or less that would keep the RF Exposure at or below below the limits. Except the Larsen NMO-2/70B (34.75" tall) antenna has gain and you would have to reduce the power to stay in the limits. On the Jeep L bracket off the hood, the groudnplane is pretty much non existent, so a half wave type antenna is better.

Not to mention RF getting back into some Ham radios that causes all sorts of problems.

 

[KK4JUG]

Interesting you say that. The #3 (on the cowl/fender) is often said by jeepers to be the #1 best place to put an antenna (assuming in the middle of the hood is a no-go). I'm not sure I believe the exposure limits anyway since it's non-ionizing radiation.

Most "jeepers" are also using CB antenna that aren't putting out that much wattage. When the OP said dual band, I assume me meant amateur radio. That could easily go up 50+ watts and it ain't good for you.

Furthermore, Faraday cage not withstanding, both UHF & VHF will get in. CB not so much.

 

[fyrfyter33]

The diamond motorized mount on a roof rack works great. I have one with a comet NMO antenna mounted to the roof rack on my highlander. It fits in parking garages and low clearance areas no issue, so I can recommend that. I think the max antenna length on it is in the 45” range and I’m well below that.

 

[mmckenna]

If you want it to work well, you mount it up high. Anything else is going to be a compromise.

High gain antennas can work against you when in mountainous area. They are certainly not "best" in all installations.

Mounting it on the fender will expose you to high RF levels, that's a choice you will need to make. Even with the body, the windows provide a big enough aperture for these frequencies, especially on UHF. Putting it down below will create a bit of shadowing.

The garaging creates some issues, but all is not lost.

I wouldn't waste $100 on a motorized mount. I'd be curious how one would really hold up off road, with vibration and tree branch strikes, I think it would really get tested.

I've used the Larsen NMO-2/70SH, and they work well. The spring at the base will let it absorb branch strikes. Solid built antennas built off their commercial/public safety line of products. I've got 30 year old Larsen antennas that I'm using.

I'd not recommend the Diamond or Comet brand stuff. Amateur/consumer grade antennas, and you won't really save any money in the long term. They won't work any better than the commercial stuff.

Don't overlook a simple 1/4 wave VHF whip. They work very well on VHF and act as a 3/4 wave antenna on the 70 centimeter amateur band. The radiation pattern is a bit funky on UHF but they work well, especially in the mountains. They are also inexpensive, less than $10. They are also very flexible and will withstand parking garages and tree branches. My dad has one on the roof of his Chevy Silverado that he parks in the garage, and the top half of the antenna hits the garage door when he pulls in. Been doing that almost every day for 3 years without failure.

The higher gain antennas achieve the gain by forcing the radiation pattern into a flatter plane. This focuses more of the energy towards the horizon. That works fine on on the flat lands, but can work against you in the mountains. The 1/4 wave antennas have a more even radiation pattern, and that can benefit when repeaters are above the horizon. More gain isn't "better", it's just different. Different isn't always best. There's good reason why 1/4 wave antennas are popular, especially on public safety systems. They are inexpensive, they work well, and they are very durable.

I'd recommend putting a pair of NMO mounts on the rack, either in the corners, or one centered on the front, and one on the rear. You could even center one on the drivers side and one on the passenger side, it's not really going to make a huge difference. Either way the ground plane is going to be lopsided. Grounding the rack might provide a good DC ground, but DC grounds are not the same as an RF ground plane, so try it first. Do install at least two NMO mounts, maybe a third if you ever plan on running CB. If CB is something you are interested in, and it can be a good option on the trail, the Larsen NMO-27 antenna is an -excellent- performer and will really take a beating off road. I've been running those for 30 years and never had one fail.

For the APRS radio, absolutely go with the quarter wave. You usually don't need high gain on APRS, you don't need dual band, and the basic 1/4 wave has the benefits I noted above.
For the dual band, either the Larsen NMO-2/70SH, or a VHF quarter wave.

Do make sure you run your radio power direct from the battery. Don't tap into existing vehicle wiring.

 

[fyrfyter33]

Agree on wiring. I won’t use anything smaller than 12ga red/Black zip wiring. 12ga gives you 20a to work with. That’s usually plenty, unless you are running dual high power mobile radios, then you might want 10ga.

Don’t skimp on the power connectors to the radio. Use something decent that’s meant for your use. If you are hardwiring it in, get the butt connectors that have heat shrink on the ends, or solder the ends and then heat shrink the wiring and solder joint.

 

[mmckenna]

Agree on wiring. I won’t use anything smaller than 12ga red/Black zip wiring. 12ga gives you 20a to work with. That’s usually plenty, unless you are running dual high power mobile radios, then you might want 10ga.

Depends on the distance as well as current draw. On a Jeep, distance isn't likely going to be an issue, but on a larger SUV, it can be. Voltage drop in long conductors can be an issue.

I usually run #6 in my vehicles and my work trucks. It allows running more than one radio, including higher power commercial radios. I fuse (or circuit breaker) for 60 amps. No concerns about transmitting with two at once (it happens, especially with trunking radios).

Don’t skimp on the power connectors to the radio. Use something decent that’s meant for your use. If you are hardwiring it in, get the butt connectors that have heat shrink on the ends, or solder the ends and then heat shrink the wiring and solder joint.

Yes, quality components pay off. Also, using the right crimp tool, too. Far too many issues I've seen with poorly installed/crimped connectors. Full cycle crimp tools designed for the size connector/wire is the right way to do it.

Ideally, don't use butt connectors. Much better to run continuous length of wire.

On my personal stuff, I often add a bit of solder on the crimp terminals. Some say it's overkill, but it ensures a good connection. Follow up with marine grade heat shrink tubing. Put all wiring in loom and properly secure. Done right, the wiring will look factory. Much easier to spend a few more minutes in your warm/well lit garage (and with a cold beer) than in the dark/rain/mud, trying to find a wiring fault when you really need your radio to work.

 

[secretspy711]

I am indeed talking about 2-meter / 70cm when I say dual-band. I already have a 4-watt CB (max legal power for CB) with an antenna on the spare tire mount.

Correct me if I'm wrong, but my understanding for RF exposure limits for 2-meters is that as long as you're operating below 50 watts, you're not in danger of exceeding the limits. (Or, at least you don't have to perform a station evaluation.) I'm currently using an 8-watt HT, just looking to connect it to an external antenna because I know from experience flying drones that the antenna can make more of a difference than power output.

mmckenna, thank you for the well-articulated suggestions. You helped me in another thread with CB noise issues that I'm still working on.

 

[mmckenna]

I am indeed talking about 2-meter / 70cm when I say dual-band. I already have a 4-watt CB (max legal power for CB) with an antenna on the spare tire mount.

OK, good info. That's what we figured. If the spare tire mount for the CB is working well, then no need to change it.

Correct me if I'm wrong, but my understanding for RF exposure limits for 2-meters is that as long as you're operating below 50 watts, you're not in danger of exceeding the limits. (Or, at least you don't have to perform a station evaluation.) I'm currently using an 8-watt HT, just looking to connect it to an external antenna because I know from experience flying drones that the antenna can make more of a difference than power output.

Amateur radio operators don't have to meet some of the same RF exposure rules that those on the commercial side do, however that doesn't mean you shouldn't consider it. An amateur radio into a fender mount antenna isn't going to kill you. Personally, and like others on here, I wouldn't do that to me or my passengers. Mostly, I wouldn't do it because I've learned that mounting the antennas correctly works better. Fender mounting is a compromise. If you are OK with that compromise, then go for it. If you want it to work well, then I'd suggest not mounting on the fender. You've got the rack system, and it'll work better. The antennas that were suggested will work with the garage issue, so there really isn't a benefit to using the fender.

mmckenna, thank you for the well-articulated suggestions. You helped me in another thread with CB noise issues that I'm still working on.

I was hoping that would be an easy fix, but alas, not. I've had some weird radio issues I've solved by grounding the radio chassis, so I usually recommend it as an easy/cheap first step. But, like others suggested, it is radiated ignition noise, and that is going to take some work to resolve. Thanks for giving it a try, though. It certainly won't hurt your install to leave the radio chassis grounded.

 

[K6GBW]

I drilled a hole in the cowling on the right side and ran an NMO mount with a short Diamond dualband antenna. I usually only ran the radio at medium power and it got out like gang busters. Never had to worry about hitting trees either!

 

[jwt873]

I'm late to this one, but I just saw this picture on the net.. A Wrangler owner fastened a metal plate to his roof rack and mag-mounted a dual bander in the middle of the sheet. Since the roof of a hardtop is pretty high, a permanently mounted antenna can be a challenge at times when it comes to garages etc. My cowl mounted dual bander 'twangs' on the 7 foot door of my garage every time I drive in and out.

A mag mount makes it easy to remove. They also make a power fold over mounts, but I'm not that familiar with them.