Antennae Placement for CB, GPS, and FM Radios

[u10072]

Hello All,
Normally on something like this I would honestly just call the manufacturers but I am hoping one of you techno/electro guys will know. I am finishing up my rollcage (family style) and want to add some mounts on the cage for a CB, a GPS and FM race radio (I want to be able to take this truck to Baja where the radios are almost a must). My question really is do the different forms of communication need to be mounted a different points? If this matters the "bikini-top" I am going to be running is going to be 16ga. aluminum. The plan at this time is basically mount the GPS antennae at one of the front corners of the cage, then the CB at the rear corner driver side, and the FM race radio in the middle on the drivers side.

If you all know this stuff please let me know,
Matt

 

[Viperwolf1]

The frequencies are far enough apart that you shouldn't have issues with them. GPS just needs a unshrouded view of most of the sky, it can go almost anywhere, even on the hood. CB antenna would radiate and receive in a more omnidirectional (all directions equally) pattern if it was centered on the ground plane (bikini top) than if it was on a corner. FM antenna is probably less picky about that than CB antenna.

 

[TwoDalesDad]

Ditto...

 

[u10072]

I am guessing for obvious reasons that putting a GPS underneath a sheet of aluminum that is not considered a unshrouded view of the sky-- hate to sound stupid but is a soft-top above the gps create any issues? Im guessing not??

 

[Viperwolf1]

GPS signals are extremely weak. I wouldn't put it under anything if you can help it.

 

[br0nc0xrapt0r]

GPS needs to be on the very top with nothing in the way of the sides or sky view. Almost anything can mask it from satellites.

 

[Airmapper]

As stated a GPS antenna likes unobstructed view of the sky. But a soft top will not knock it's signal that severely. I use my handheld a lot in the Bronco with a canvas bikini top and have no ill effects, and a handheld uses a small internally mounted antenna. I also use it in my SUV mounted to the windshield with no issues.

Any metal covering will knock it severely, however non-metallic coverings won't bother it that much. I'd avoid it if I could, but canvas over it shouldn't create a problem, especially if you need something to hold you over until you can put it in a better spot.

 

[br0nc0xrapt0r]

I always run a external antenna at all times but then again I'm using the Y code not C/A ;D

 

[Viperwolf1]

GPS needs to be on the very top with nothing in the way of the sides or sky view. Almost anything can mask it from satellites.

For the purposes of road navigation this isn't neccesary. It's not like he's trying to precisely survey a location with cm accuracy. That's why I said unobstructed view of most of the sky. He'll see plenty of sats and get pretty good results with minor obstructions. Use the high ground for the important stuff like 2 way comms.

 

[br0nc0xrapt0r]

For the purposes of road navigation this isn't neccesary. It's not like he's trying to precisely survey a location with cm accuracy. That's why I said unobstructed view of most of the sky. He'll see plenty of sats and get pretty good results with minor obstructions. Use the high ground for the important stuff like 2 way comms.

Sometimes I go a little overboard with my GPS accuracy ;D

 

[pbwcr]

Ant Location

Hi Matt,
Here is your long answer form lots of real experience.

Radio signals do not go thru metal. All thes gadgets use radio signals.
If you have a GPS with an internal ant just mount it close to the windshield. Same thing for Sirius/XM ant. Having said that. With your metal roof I would put them on top.
Your vhf and CB radios will need a whip antenna. For best result place them on your metal roof and use an "LMO" for the penetration.
Separation of the antennas is minimal for the above. My Baja rig are about 10" apart and they work fine. I have 2 vhf radios and for sure you cannot transmit on both at the same time, however you can listen on both at the same time.
For a dual purpose rig (us & Baja) you have to have both a CB and a vhf radio. CB transmit distance is nothing in Baja and nobody even has them.

My EB dedicated to the US has a dedicated stock top and I did not want to hole the top so my am/fm and my CB ant are mounted about 2' apart on the rear tire carrier. Sirius is not installed yet , but I will put it on the roof near the windshield. My Lowrance & Garmin GPSs are both hand helds with internal ant so they are mounted on the windshield with suction cups. They work fine.
Buy a big time Lowrance with external ant then it has to see the sky -not looking thru metal.

So how do the VHF & CB work on the tire mount compared to a metal roof mount? Answer is they are marginally ok, but a metal roof mount is probably 3-4 times better. Reason is no ground plane. The vhf units come from 25 to 110 watts and they perform as expected more watts are the answer.
Consider a fiberglass roof, then all can be mounted on the cage.

PaulW

 

[u10072]

Thanks for all the replies-- I am thinking that I am going to move the GPS remote ant to the passenger rear and mount it to the cage and cut a hole in the "bikini" top so that if I want to just run with no soft or bikini then the GPS can see the sky-- and if I still have the aluminum bikini on and the soft top installed the GPS will still work-- the GPS will just poke through the aluminum sheet if that makes sense. As far at the soft top I am going to run the Rampage-- mainly because the Besttop riser is just terrible to look at, very stupid I know. I am thinking that I can have the top modified at the rear drivers corner to allow the CB and FM ant poke through and still have some weather resistance.

So my next question is if I mount the 2 ant (CB and FM) about 6" apart and still be fine. I was thinking of using a smaller antennae like about 24". Being this isn't a prerunner only and has a soft top doing this type of stuff on an EB is kind of a bitch!

 

[Viperwolf1]

The further you can get them apart, the better they'll be. I suggest mounting them up temporarily and testing. Make sure to run the cables separately also. Don't run them next to each other.

 

[u10072]

I really need to run the wires together-- how about using the aluminum foil trick like Ford used on the TFI? Heres the deal-- if I run them in different spots my rollcage ends up looking like one big wire loom gone amuck-- with that said its gotta work though.......

 

[Viperwolf1]

Why not run one of the cables through the cage tubing?

 

[u10072]

Well its for a couple reason-- if you run the cable through the cage its such a huge pain to do so, it also degrades the structural integrity of the cage, and I have been around enough off-road races/events to know that the cables, radios and cb's fail all the time-- all the time. There has to be a way to package this stuff together-- whats your thoughts on the "foil-taping" route?? There has to be a great creative route fix to this problem....

 

[Viperwolf1]

Well, the foil (if grounded) would be better than just running the cables next to each other. Might not be pretty but you may be able to hide it all inside some convoluted tubing or something.

 

[pbwcr]

On all my rigs I like a clean look for cables like coax and various lights. What I do is run the stuff down low inside the body for protection and out of sight. Of course the end use of the stuff is usual high on the cage or on the top or on the rear cage tubes. Or an interior overhead light might be on a cage tube up high.
So as soon as the wires/cables become visible I route them in the conduit sold at Home Depot. Conduit is sticky back and I clamp then for several days with zip ties until the adhesive sets. The ones I use will hold 2 fat coax or a half dozen single wires. After a few days I paint them the same color as the cage tubes.
I usually do each one several times until I an happy with the look Ha.
The result is the sticky stuff goes bad so it has to be replaced and I get to start over. Sigh.
BTW I have never has the wires or cables talk to each other. Its a non issue.
PaulW