Page 1 of 1
Two radios, Antenna placement
Posted: Thu Jun 20, 2013 8:32 am
by cs_drums
I am goint to install another radio in my bronco. What are the does and dont of 2 antennas? Can I just put them right next two eachother or is there a minimum distance apart they chould be?
Thanks!
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 11:02 am
by BDKW1
Equal spacing side to side in the center of the roof. They should come out almost directly above your head.
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 11:03 am
by Phoenix0783
I'm not sure but you probably want them some fraction of the wavelength apart. Half maybe?
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 11:10 am
by BDKW1
Not going to happen on a Bronco roof, not enough real estate.
Now if you put a foil sheet on the top of the shell for a ground plane and centered on in the shell and one in the roof you would be able to do that.
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 11:14 am
by tcm glx
I have one over my dome light, and another on the middle of the roof... approx 15" apart. PCI recommends a minimum of 18" seperation, but I could not pull that off.
I went ahead with the 15" anyways, because quite honestly, the purpose of two radios is for seperate monitoring. Yes, there is interferance if I try and talk on both, but I am rarely ever doing that (why would I......)
So the setup I have works awesome... one radio is just constantly monitoring the weatherman or race frequencies, and one is being used for Comm.
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 11:56 am
by 300
Speaking of ground planes on fiberglass roofs, saw my father in law successfully 'glass a chunk of metallic window screen on the interior of his fiberglass shell.
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 12:04 pm
by cs_drums
tcm glx wrote:I have one over my dome light, and another on the middle of the roof... approx 15" apart. PCI recommends a minimum of 18" seperation, but I could not pull that off.
I went ahead with the 15" anyways, because quite honestly, the purpose of two radios is for seperate monitoring. Yes, there is interferance if I try and talk on both, but I am rarely ever doing that (why would I......)
So the setup I have works awesome... one radio is just constantly monitoring the weatherman or race frequencies, and one is being used for Comm.
Thats what i will be using it for. I alreade set on up centered on the rige befor the shell. I was told after the fact that center of the roof would have been better. I may do the next one there.
BDKW1 wrote:
Now if you put a foil sheet on the top of the shell for a ground plane and centered on in the shell and one in the roof you would be able to do that.
I was thinking of this. Im painting it soon so now would be the time to do it! Woult it really make a huge difference from Tony's set up?
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 12:38 pm
by PaulW
cs_drums wrote:I am goint to install another radio in my bronco. What are the does and dont of 2 antennas? Can I just put them right next two eachother or is there a minimum distance apart they chould be?
Thanks!
===
If you want to transmit both at the same time - bad
If all you do is listen on both and transmit on one then all is good. Mine are 6" apart center of the metal roof, and both work fine. Put em close and a single protector will do. Do a lot of research before you use a spring because the RX/TX quality is terrible when the ant swings back & forth.
A single antenna center of the Bronco metal roof is great because the ground plane is close to ideal.
For the glass roof: metal inside or out about 3' radius would be good. Foil or AL screen is good. Make sure the shield connects to the GP and to the vehicle ground. You can get good success with copper foil radials with a center at the antenna. Common deal for glass airplanes.
Open buggies/racers with only a cage to bolt the ant to results in marginal performance due to minimal GP. Common issue with jeeps who put the ant on the tire carrier. Better to put the ant on the metal hood then the performance is excellent.
PW
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 2:31 pm
by cs_drums
I was gonna ask Tony to post a pic of his set up but then I remembered I have the magazine on my night stand haha
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 2:41 pm
by tcm glx
cs_drums wrote:I was gonna ask Tony to post a pic of his set up but then I remembered I have the magazine on my night stand haha
Picture as requested. Not sure I had both in te magazine shoot.

Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 3:45 pm
by Travisfab
I thought the antenna's that did not require a ground plane could be mounted anywhere, shell for example.
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 3:48 pm
by cs_drums
Travisfab wrote:I thought the antenna's that did not require a ground plane could be mounted anywhere, shell for example.
Is this an option?
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 4:36 pm
by Seabass
I think the antennas with out a ground plane are larger and have the prongs radiating around the main untenna making them less desirable for mobile installs.
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 4:48 pm
by BDKW1
NGP (no ground plane) antennas have a coil at the base ot compensate for not having a GP. They generally do not perform as well as GP models. Lengths are within a couple of inch's of each other.
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 4:56 pm
by PaulW
Local Jeepers tried NGP for their CBs. No good at all Waste of $. Range is much less tx/rx.
Theory same result with VHF & UHF
Do it correctly and you will be happy
Different result with a base station ant which has the whiskers up top for the GP.
PW
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 5:09 pm
by Seabass
If your setting up a base camp running a NGP antenna on a mast is an alternative to running a second antenna on your roof with the potential for added reception and reach.
I have a ham geek buddy that showed me how to moniter multiple stations and set priority with my radio. It's way to complicated for me. There is a benifit to two radios that have dedicated channels.
FYI: there is a perfect storm senario my ham geek buddy warned me about. If your transmitting on one and the antennas touch there are some radios that can be damaged. WAY too techy for me to keep up but it stuck that expensive electronic whatsamahoosits may have the smoke let out if I bounce around while pushing buttons.
I rarely need to moniter two channels and if I do we chase in packs So theres usually more than one radio.
Re: Two radios, Antenna placement
Posted: Thu Jun 20, 2013 6:36 pm
by BDKW1
PaulW wrote:Local Jeepers tried NGP for their CBs. No good at all Waste of $. Range is much less tx/rx.
CB's have to long of a wave, they really need GP's. The higher you go in the freq range the less the performance difference between GP and NGP antennas. VHF is about a DB off, UHF is only about .5DB less.