HF antenna mounting considerations...

Submitted: Friday, Mar 04, 2005 at 14:23
ThreadID: 20960 Views:5460 Replies:8 FollowUps:7
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Hi Everybody,
I'm wondering what options there are for mounting a Codan 9350 antenna on a 2004 Prado. I have been asked by a friend for some help in the matter.
I seem to recall that having them on the bullbar is a no-no these days. Can someone point me to the legislation that refers to obstructions to the drivers vision such as HF antennas?
The other option I have is to mount it on the back door with some sort of bracket that shares the spare tyre mounting point. Is there an off-the-shelf antenna mounting bracket that is ready to bolt on??
Does mounting an antenna on the back increase the stresses on the door too much?
Please help....
Regards,
Michael.
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Reply By: Member - Banjo (SA) - Friday, Mar 04, 2005 at 14:29

Friday, Mar 04, 2005 at 14:29
Mob in northern suburbs of Adelaide make such custom brackets - Aust 4WD systems - link on the "links" page at vks7737.on.net (Offraod Equipkent section).
They may be doing one for te Prado. Mine for the Jack is at the rear in behind the spare - seems quite sturdy - has served me well. Note that if its on the front, it can be hit by "things" and the autotunes are costly !
AnswerID: 101117

Follow Up By: Member - Banjo (SA) - Friday, Mar 04, 2005 at 15:20

Friday, Mar 04, 2005 at 15:20
er....re my above post ...I should check my cyber scribble - that line should read ... vks737.on.net (Offroad Equipment section)....
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FollowupID: 359127

Reply By: Member - Landie - Friday, Mar 04, 2005 at 14:34

Friday, Mar 04, 2005 at 14:34
Good question. I am NSW based and have tried to glean the same information.

I have a HF Self-tune antenna mounted on the front bull-bar, however the mounting complies with the RTA guidelines. An inspection station has approved it on this basis.

It has been suggested that it might be viewed as an obstruction, however there appears little guidance on this point.

Consequently I have written to my State MP and asked them to seek clarification from both the Police and Transport Ministers, this is currently underway.

My suspiciion is that there are no firm guidelines on this point (vision obstruction)and at the end of the day, one should assume it is a State issue (RTA in NSW) as it is a vehicle modification and they are covered under State laws. Going back to the RTA guidance on bullbars, mounting HF antennas on the bullbar does not appear to be excluded, providing it complies with the directive they have issued.

I'll post the responses I receive in due course.

Landie
AnswerID: 101120

Reply By: BenSpoon - Friday, Mar 04, 2005 at 17:57

Friday, Mar 04, 2005 at 17:57
It seems that autotunes mounted up front are generally acceptable, it is more the position on the roobar that can cause dramas. Having them protruding beyond the front face of the roobar is a danger, and can be picked up on- this was mentioned in a recent post.
I have not heard of people coming to strife with the law over a front-mounted aerialwith the impaired vision matter, but as mentioned before due to the nature of our kangaroo magnet cars, rear mounting is certainly prefferable and would get you around this.would this do? (centre wheel mount)
AnswerID: 101145

Reply By: Footloose - Friday, Mar 04, 2005 at 19:10

Friday, Mar 04, 2005 at 19:10
They work better on the front, but not enough to risk the wrath of any applicable laws or the insurance company.
If front mounted, imagine a person hell bent on committing Hari Kari in front of your vehicle. Now, should that unfortunately happen, how far do you rekkon your insurance company would go to defend any litigation? About as far as the aerial !
AnswerID: 101154

Reply By: Smudger - Friday, Mar 04, 2005 at 20:00

Friday, Mar 04, 2005 at 20:00
Just recently fitted a UH to my Disco. After looking around I decided to use a gutter mounted antena, chrome mounting bracket cost about $20. Does the job real well and when we get back from the bush it can be removed in about 2 minutes. I don't leave the radio in the truck full time, been broken into a couple of times and don't want to lose it. Same with antena, they are prime targets. And if they're too high you can't get into shopping centre car parks. Besides, mostly you only get rubbish on UH in town.
Catch you on the air one day.
AnswerID: 101161

Follow Up By: Member - Roachie (SA) - Sunday, Mar 06, 2005 at 22:00

Sunday, Mar 06, 2005 at 22:00
G'day Smudger,
I think you might have misread the question. asking about "HF" antenna, whereas you mention "UH" which I assume you mean "UHF" (based on your statement that you mount your antenna on the gutter of your vehicle).
HF Antenna's (the auto-tune variety anyway) are the quite large units you'll often see........about 3 foot high and about 30mm or more in diamter. They then have a whip type antenna on top of that, making them anything up to 8 feet tall.
Cheers,
Roachie
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FollowupID: 359329

Reply By: Ray Bates - Friday, Mar 04, 2005 at 21:23

Friday, Mar 04, 2005 at 21:23
Hi Guys,
I live in WA and was planning a trip accros to the east in may but after reading on here about NSW I think that will give that state the flick. Too many rules and regulations there
AnswerID: 101173

Reply By: Bob of KAOS - Friday, Mar 04, 2005 at 23:19

Friday, Mar 04, 2005 at 23:19
I mounted an ordinary tapped whip on the rear door of the Disco. No problems there. I inserted an 'L' shaped piece of bracket steel between the tyre mount bracket and the door panel. I just drilled a half inch hole in the horizontal bit to accept the Benelec antenna mount. I am sure it works just as well on the back of the truck as on the front. In addition, it won't be the first thing detroyed in a frontal impact (although a rollover would sorely test it).
AnswerID: 101182

Follow Up By: Footloose - Saturday, Mar 05, 2005 at 12:54

Saturday, Mar 05, 2005 at 12:54
Bob, although rear mounting does afford some protection it also has disadvantages. It's easy to forget you have it on if parking under something, especially servos. One guy I know took out a lotta floros at a fuel stop. Since you can't see the whip of an autotune mounted on the rear, if it gets whacked by a tree branch or falls off on corros then you might not realize it until you need it.
Dammed if you do and dammed if you don't I rekkon :))
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Follow Up By: Bob of KAOS - Saturday, Mar 05, 2005 at 16:06

Saturday, Mar 05, 2005 at 16:06
Thats true. I have scraped the roof of the roadhouse - no damage luckily.
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Follow Up By: Tuco - Saturday, Mar 05, 2005 at 18:35

Saturday, Mar 05, 2005 at 18:35
I have used HF taped whips and also Barrett autotune units both on the bullbar and also on a rear wheel carrier mount and have found that the rear mount is better for a number of reasons.

1. Visibility is not restricted at all with a rear mount autotune.

2. Interference from alternator whine, electronic fuel injection (petrol or diesel), spark plugs, plug caps and leads (petrol) when using the HF in a mobile situation is much reduced in a rear aerial setup. Many people only ever use their HF when stationary without the engine running - so no difference. On some vehicles that we have owned, we were not able to use the bullbar mounted aerial when mobile - simply because of the noise interference. By moving the aerial to the rear of the vehicle mobile communications were possible.

3. Toyota and also some other vehicle manufacturers warn of the possible damage that high powered HF transmitters may do to the electronic engine management sysyem on modern vehicles. By locating the aerial at the opposite end of the vehicle and away from the ECU - then the risk is minimised.

The radiation pattern of either bullbar or rear mount is very poor. The centre of the roof will definitely provide the best omnidirectional pattern. BUT how many of us could accomodate a long whip on top of our vehicles - not practicle.
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FollowupID: 359222

Follow Up By: Footloose - Saturday, Mar 05, 2005 at 18:48

Saturday, Mar 05, 2005 at 18:48
You are correct up to a point. See http://groups.yahoo.com/group/codan_outback_radio/files/Auto%20Tune/
to dispel some common home "truths" on front vs rear mounting.
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FollowupID: 359223

Follow Up By: Tuco - Sunday, Mar 06, 2005 at 12:35

Sunday, Mar 06, 2005 at 12:35
Hi Footloose - that is a very interesting test that Codan have done with regard to the radiation pattern. Clearly shows that it isn't linear either with some bands improving by as much as 2dB while some are 9dB down.

Most of my galah sessions are on 5145 or 6950 and so far haven't had readability complaints.

My bottom line is that with the rear mount I can use the HF mobile, but with a bullbar mounted aerial - too much electrical interference noise.

Cheers - thanks for the link.
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FollowupID: 359272

Reply By: lindsay - Sunday, Mar 06, 2005 at 10:08

Sunday, Mar 06, 2005 at 10:08
Micheal. I have my HF auto tune on the Bull Bar and it has 2 mounting points, one is that it sits down on the bumper bar section at the side when we are not in the bush. When we go bush I move it to the top of the Bull Bar to the centre of the vehicle. I have found that with two identical radios and the auto tune on mine in the lower position and another in a position on top of the Bar my radio did not recieve or transmit as good as the one on topof the bar. You will find that the part of the base will need to be clear of obstructions to operate adequately, it will operate but when you need it in bad conditions it will make a difference. The other aspect is that if the antena is in front you will be able to observe it in areas where there are overhanging branches ect. In Victoria on www.vicroads.vic.gov.au there is a vehicle standards information section look at No 29, it deals with the field of vision and is quite explanitory. I run my self tune to comply that document at home and if I ever get pulled up I will relate to that. In the bush I am quite happy to take the risk knowing that I can always just remove the antena to the lower position.
AnswerID: 101296

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