Antenna mounting/installation

Submitted: Sunday, Oct 26, 2003 at 17:28
ThreadID: 8097 Views:1945 Replies:5 FollowUps:5
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I'm about to install my AM and UHF radio's aerials on the bullbar. They are both ground plane independant but my question is: should I route the co-ax from each aerial to seperate sides of the engine bay to reduce interference or is it ok to run them both down the same side? One side of the bay is a lot easier to get thru' the firewall.
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Reply By: Member - Eric- Sunday, Oct 26, 2003 at 17:36

Sunday, Oct 26, 2003 at 17:36
I think it would be fine down one side , I would insulate them through seperate condute tubes Venus Bay
AnswerID: 35159

Reply By: Member - Bob L - Sunday, Oct 26, 2003 at 17:44

Sunday, Oct 26, 2003 at 17:44
You can use the same access through the fire wall (GU has access both sides)and run coax side by side.
Keep coax away from excess heat as I have seen the centre wire melt through the insulation with no external damage evident.
Also if your using a spring mounted antenna leave a little slackat the base as it will take up coax when bent over.
Cheers Bob

AnswerID: 35163

Reply By: joc45 - Sunday, Oct 26, 2003 at 20:19

Sunday, Oct 26, 2003 at 20:19
Another thing is not to mount the antennas (antennae?) too close to each other; the proximity to each other affects the performance.
AnswerID: 35170

Follow Up By: Andy - Sunday, Oct 26, 2003 at 20:47

Sunday, Oct 26, 2003 at 20:47
What would be the minimum distance the antennas should be apart ?
FollowupID: 25407

Follow Up By: joc45 - Sunday, Oct 26, 2003 at 21:25

Sunday, Oct 26, 2003 at 21:25
Andy, ideally, they should not be closer than about 1/2 wavelength, but this is not possible with the 27MHz AM. If you can do it, opposite ends of the bullbar would be your best compromise. (1/2 wavelength at 470MHz is about 320mm, but at 27MHz, this is about 5.5metres). Your system will work if you put the antennas close together, but with diminshed performance, even if you readjust for vswr. I see lots of installations where the antennas are about 150mm apart, and I guess they work.
Running the coax cables close together should introduce no interference.
FollowupID: 25416

Follow Up By: Groove - Monday, Oct 27, 2003 at 14:06

Monday, Oct 27, 2003 at 14:06
I read somewhere a minimum of 60cm apart, dont remeber where I read it. Bottom line further apart the better.
FollowupID: 25469

Reply By: chrisfrd - Monday, Oct 27, 2003 at 17:55

Monday, Oct 27, 2003 at 17:55

I do lots of 4x4 electrical systems in Canberra and I always place each antenna 400mm apart. I run the coax feeds down to the antennas by zipping them up in split tubing, then tightly binding the tubing with Nitto Electrical Tape. This makes them look like original cabling.

Another trick with Nissan GU/GQ Patrols is to remove the bottom grommet and remove the ABS wiring, for trucks that have no such facility. You then have a fully usable grommet, to which you can install into, then tape up to make it look like a factory install.

I always run the cabling out from the grille, then through to the bullbar in one run, dropping the feeds from the tubing by back-taping them. This keeps the water out of the tubing. Please make sure that you have correctly waterproofed the cable connectors and such. Additionally, ensure that you comply with the latest DOTARS and RTA requirements for hard-points on a bullbar, by ensuring that there a no protruding points pointing forward of the bar line.

AnswerID: 35279

Follow Up By: Member - John - Tuesday, Oct 28, 2003 at 00:51

Tuesday, Oct 28, 2003 at 00:51
Chris, just a quick question. Which one is the ABS grommet? Have a GU with out ABS. Thanks in advance.
FollowupID: 25540

Follow Up By: chrisfrd - Tuesday, Oct 28, 2003 at 11:34

Tuesday, Oct 28, 2003 at 11:34
Ok, when you are looking inside the engine bay, stick your head down near the auxilary battery on the passenger side. You will see a gromet there that has some cables coming out from it, these will be clipped-up out of the way on the wheel-well.

From within the car, remove the door scuff-plate by pushing your fingers into the carpet at one side and pulling directly up, fairly firmly. Don't go too far, otherwise you will break the plastic! Remove the kick panel, the carpet screws from the foot well and pull the carpet out of the way. Now you can remove the grommet, the cables and everything from within the grommet. I pulled the wires from the the connectors and did them back up again, alternatively, you can cut and tape them up out of the way, as they were for the ABS system that you don't have. If you want to keep everything intact, simply untape the grommet and force your cabling through.

A hint... If you want to make it easy, get some KY gel and smear it on the cable. This is a water-based lubricant and is safe for use on the cables, it simply dires out and goes into a fine powder, that can't damage the cabling.

FollowupID: 25558

Reply By: Member - Tim Nivo - Monday, Oct 27, 2003 at 21:18

Monday, Oct 27, 2003 at 21:18
G'day Andrew. One trick I learnt the hard way, don't run your cables through the grill. A so called expert did this to me. Worked great until I had to clean the radiator and could'nt get the grill off. Had to rerun all the cables, as they normally don't disconnect at the antenna end. Good Luck. Tim.
AnswerID: 35309

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