HF Radio Antenna

Submitted: Sunday, Sep 14, 2003 at 19:41
ThreadID: 7223 Views:2193 Replies:9 FollowUps:4
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About to install a radio to my GU Patrol it is down to the codan or the barrett will proberly go with the codan due to size and the fitting of the equipment, in regard to the fitting of the attenna i want to fit it to the rear wheel carrier swing arm on the drivers side has any one had any experince on fitting one there and if this is a suitable place for reception and transmisson.
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Reply By: Martyn (WA) - Sunday, Sep 14, 2003 at 21:56

Sunday, Sep 14, 2003 at 21:56
10 Para,
I have a GQ, I have the Barrett 550 with a remote head, a good unit when it's set up correctly. With regard to the antenna, I'm still trying to find an auto tune but I have my multi tap on the rear wheel carrier, I've been told that the idea is to try and keep any other antennas as far away as possible, I have a UHF on the bull bar, can't get it much futher away, so that's good. I've planned to have mine with the top of the auto tune only a little bit above the roof line with the whip bit going from there. I find that when I'm going forward concentrating on the front bit I tend to forget the back bit, many a time I've forgotten the multitap only to hear the twigs and sticks landing on the roof as I go under low branches. The higher the antenna the better from what I know, and other antennas close effect the reception. Hope some of this helps.Keep the shiny side up
AnswerID: 31036

Reply By: Mad Dog Morgan (Vic) - Sunday, Sep 14, 2003 at 21:57

Sunday, Sep 14, 2003 at 21:57
I've seen a number fitted on the rear so it may work but testing done by Codan has shown the top of the bull bar to be the best place. It's got me beat how these little whips get the signal out below the 15 metre band, next best thing to a dummy load maybe :)My Best Mates
AnswerID: 31037

Reply By: Steve - Sunday, Sep 14, 2003 at 23:39

Sunday, Sep 14, 2003 at 23:39
Got a Barrett auto tune unit stuck up the front of my L/C ... out on the bull bar, and wanted to put it up the back on the wheel carrier to get ot out of the way , and was advised that while in theory this was OK it was likely that the reception would suffer .. ( also would get in the way of the roof top tent !!) So it's still out front and it will stay there ..looked at a Codan NGT !! but wife found it too Hi Tech .. so went for the Barrett... its got the simple press Red Button (if all else fails) and she is happy as ........ with that system !!! Reckon she is waiting for the day she can use it ..
AnswerID: 31045

Reply By: Sapper - Monday, Sep 15, 2003 at 13:14

Monday, Sep 15, 2003 at 13:14
There is no problem with fitting the antenna anywhere on the vehicle. However if you want the best radiation from a whip and that radiates 360 deg, then it must be above the vehicle line for optimum radiation and ground wave. When fitting HF ensure that all aspects of the vehicle are grounded well. This will limit the noise factor. When I used to fit them we had suppressors, and earth links all over the vehicle, chassis to body etc. Reduced noise to minimum and produced a great result on the equipment.

Good travelling

AnswerID: 31083

Reply By: landie - Monday, Sep 15, 2003 at 14:21

Monday, Sep 15, 2003 at 14:21
I have a Barrett 950, with a 910 auto tune antenna. I was going to stick it on the back of my Defender, but was also advised that its ability to function at an optimal level "may" suffer. Given HF is not an exact science, and the difficulty in quantifying the impact it would have if it was rear mounted, I went the bullbar option.

That opens another can-of-worms, the legaility of it being mounted on the bullbar. I am in NSW, and as far as I can see it is not a problem, providing nothing protrudes in front of the bar. Then someone pointed out that it "could" be argued it obstructs the vision of the driver. In the end I simply took the view that it is a safety thing for me, and if I'm in an emergency situation I want to give it the best chance of working as efficiently as it can.

As a footnote, when I purchased my unit, the 910 antenna was failing to autotune on a regular basis. Sometimes after only 2/3 goes at trying to get through on a frequency. After trouble shooting (the whole system) with a HF technician we replaced the antenna with another one (from the same batch), and it still failed. Finally we tried one that was not within the serial number range of the first two, and it hasn't failed since.

Barret have not offered an explanation, however I wonder if there are other antennas out there, from the same batch as the first two I tried, that may be faulty?

AnswerID: 31088

Reply By: Rob S - Monday, Sep 15, 2003 at 16:56

Monday, Sep 15, 2003 at 16:56
Continuing the discussion on where to mount....

I saw a well prepared green Defender in Cape Yorkwith the Baratt autotune
mounted in a very clever way on the back of the vehicle:

The owner had mounted what looked like some scaffold tube vertically
up against the vertical rear of the vehicle. The mounts allowed the circular
scaffold tube to slide up and down about 2 feet and could be locked in up or
down position with a hefty pin. The autotune bolted to the to of the scaffold
tube. The cables were routed to allow the up/down movement.

This allows the vehicle to be driven with the top of the autotune base at or
around roof level, but could be raised so that ALL the base unit is above roof
level when parked to allow optimum TX/RX.

Now the Defender is a great vehicle for modifying like this - but perhaps
a similar mount could be made for a rear wheel carrier for a LC or Patrol
type vehicle where there is no convenient vertical surface for bolting to.

AnswerID: 31105

Reply By: Member - Fred - Monday, Sep 15, 2003 at 17:26

Monday, Sep 15, 2003 at 17:26
Might be a good idea to check the legality of bull bar fitting - not sure if it is a national road rule but in SA [I think the rule is] that the thick bit must not protrude above the bonnet line ie not impede the driver's vision
AnswerID: 31114

Follow Up By: Spanky - Monday, Sep 15, 2003 at 18:50

Monday, Sep 15, 2003 at 18:50
I bet the SA cops have great big thick ones sticking up above their bull bars as the cops in every other state have. I have not known or heard of anyone who has been fined or defected for having an antenna on the bull bar. Have you????
FollowupID: 22083

Follow Up By: Troopyboy-vk3hsc - Thursday, Sep 18, 2003 at 16:06

Thursday, Sep 18, 2003 at 16:06
Well, I had a chat with a friend of mine in the Traffic Cops here in vic and he said to check out the Road Rules Victoria, which are based on the Nationally agreed Regs from 1999
Here's what it said.......

r. 297
(2) A driver must not drive a motor vehicle unless the driver has a clear view of the road, and traffic, ahead, behind and to each side of the driver.

Now, he said the definition is pretty broad, but anything in the line of the drivers vision from the drivers seat greater than 4 inches (thats 10cm for those of us who don't speak the old language) may be consdiered to obscure vision. So, it's more likely that if you bleep the copper off, s/he might go ya for the autotune. If it protrudes in front of the bull bar it can be deemed a "dangerous projection" or something

About the cops having them..... There are all sorts of exemptions for Emergency Vehicles, like driving and using a mobile etc

I know a guy who got nicked for having am Autotune on the bullbar in NSW, but they way he described it, he started by giving the guy some serious attitude, after doing 120 in a 100 zone, so maybe he had it coming?????

anyway wasn't that boring!!

FollowupID: 22343

Reply By: ToyMotor - Monday, Sep 15, 2003 at 19:59

Monday, Sep 15, 2003 at 19:59
... if this is a suitable place for reception and transmisson.

It will certainly be a lot more suitable after hitting a kangaroo or something even more solid, which is just when you might like to use the radio! Rear mounts perform well as long as the whip and/or autotune coil are not too close to the metallic bodywork.

AnswerID: 31152

Follow Up By: 10 Para - Monday, Sep 15, 2003 at 20:18

Monday, Sep 15, 2003 at 20:18
Hi ToyMotor why does the body have effect on the autotune and does one have to get it above the roof and if so by how much, thanks for all the replys everyone still undecided on the placement of the thing but will go with the codan unit.
FollowupID: 22096

Follow Up By: ToyMotor - Monday, Sep 15, 2003 at 20:34

Monday, Sep 15, 2003 at 20:34
The autotune is essentially a coil adjusted by a motor-driven slug (steady on there, keep it clean folks!) The proximity of metallic objects will increase losses in the coil, and may do nasty things to the tuning ability. (Some of you will have already spotted I'm trying to be non-technical here)

The manufacturer will have a spec of how close you can go to the body. Have a look at the Barret website for their mounting instructions. There is no need to have the autotune above the body, but it's definitely a good idea to have the whip above roof-line if mounting on the rear.

Also, where HF whips are concerned, bigger is better, all other things being equal. Small whips can be tuned to provide a good load to the transmitter, but effective radiated power is what we want! This will also have the benefit of maximising received power - good antennas work both ways.

FollowupID: 22099

Reply By: Ronnie - Monday, Sep 15, 2003 at 21:22

Monday, Sep 15, 2003 at 21:22
10 Para,
I have a GU and have a Barrett 550 with a remote head,the Autotune is mounted on a bracket behind the spare wheel,works fine used it last year on the Canning and up in the Gulf 3 weeks ago the bracket was recomended by Barrett. I purchased it from Aust. 4wd storage in SA.you can get a glimpse of it on my rig photo.

http://www.aus4wdstor.com/Gone Fishing
AnswerID: 31170

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