Amatuer HF radio in GU Patrol (Icom 706)

Submitted: Sunday, Jun 19, 2005 at 11:00
ThreadID: 23981 Views:4258 Replies:8 FollowUps:11
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I'm planning on putting an Icom 706 with an AH-4 tuner in my patrol.

I want to put it so that I can easily disconnect it and use it in my house.

I will run 25-30 amp cables direct from the Aux battery (both fused at the battery for 25 amps).

I am planning on mounting the transceiver on the cargo barrier, high enough so I don't worry about it getting wet if a bit of water comes in the vehicle. I'll be getting the remote head cable, and will mount that somewhere on the dash.

I plan on putting the VHF/UHF antenna on the bullbar (drivers side, with a CB UHF antenna on the passengers side)

So far so good (although open to any further suggestions for those options)

Now as to the HF antenna. I plan on putting a whip on the roof rack (to get height and to get the RF radiation away from me, and as far away from electrical interferrance from the engine bay). I have read that the lead from the AH-4 to the antenna should be very short, so I am planning on mounting the tuner on the underside of the roof rack, mounting the unit centre rear of the roof rack.

Anyone got any suggestions on how to get the coax and the AH-4 control/power lead out onto the roof? My temporary solution is to run it out a passenger side window, with the window closed almost completely....however thats just a temporary solution! I'd prefer not to have to drill a hole in my roof if possible!

I've posted this on several ham email lists and got some good solutions from the wiring side of things, but no real answers on how to run the leads out onto the roof.

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Reply By: Mad Dog (Australia) - Sunday, Jun 19, 2005 at 11:24

Sunday, Jun 19, 2005 at 11:24
Dog, how about through the firewall into the engine bay and up the inside of the snorkel.
AnswerID: 116343

Follow Up By: Dog (NT) - Sunday, Jun 19, 2005 at 11:40

Sunday, Jun 19, 2005 at 11:40

Now thats something I hadn't considered...

Only concern there is that I would be taking the coax from the centre of the vehicle, up towards the front, into the engine bay (even though its a diesel, there is still a lot of electrics there) and then up through the snorkel (even along the outside of the snorkel is an option.)

That would over double the coax run, which will increase the probability of interferance.

But its certainly worth looking at, and I could do it temporarily by running along the outside of the snorkel and coming up through the gap in the bonnet, and if I don't get any interferrence, I could then go up inside the snorkel.

Thanks for the idea.
FollowupID: 371869

Follow Up By: Mad Dog (Australia) - Sunday, Jun 19, 2005 at 21:44

Sunday, Jun 19, 2005 at 21:44
No probs Dog. What you will have here in essence is a base loaded antenna so for max performance you must maximise the groundplane with lots of bonding, use strap (skin effect), you cannot do too much bonding, the shield from RG8 works well. If noise is still a problem a static drain such as found on aircraft can do wonders.
FollowupID: 371946

Reply By: Mike Harding - Sunday, Jun 19, 2005 at 11:38

Sunday, Jun 19, 2005 at 11:38
Is it possible to take the antenna cable out through the seal between the rear doors and the body? There is often enough compression left in the seal when the doors are closed to allow this or you could cut a bit out of the seal and refill with mastic?

On the subject of two fuses in the supply lead; I have seen this a number of times and am unsure why it is done? A fuse is a resistor and will drop some voltage when in normal use - obviously two fuses will drop twice as much voltage and at 12V a drop of 1V is an 8% reduction in output power so unless there really is a good reason I would go with just one fuse.

Mike Harding
AnswerID: 116350

Follow Up By: Mad Dog (Australia) - Sunday, Jun 19, 2005 at 11:52

Sunday, Jun 19, 2005 at 11:52
Mike, the - is fused to stop it being used as a return if the main battery earth cable should offer high resistance or go open. I think all manufacturers of amateur gear fuse both lines, well all the radios I've had at least.
FollowupID: 371873

Follow Up By: Mike Harding - Sunday, Jun 19, 2005 at 12:41

Sunday, Jun 19, 2005 at 12:41
Hi Ray

Yep I see where they're coming from. If the radio chassis is connected to the vehicle framework (as it usually will be) then there is a possible current path from other equipment (also connected to chassis _only_) back to battery 0V via the neg. supply lead to the radio.

Personally I don't think I would worry too much about it. If the connection becomes bad at the battery terminal chances are the connection to the radio neg. lead would also be bad. And you could always fit a 2nd smaller lead from battery neg. to chassis to avoid issues at the chassis end. And even if heavy current did flow back through the radio it would follow the metalwork of the radio and just cause damage to the neg. supply lead. Maybe fit a 50A or 60A fuse in the neg. lead? Low resistance but will act as a last ditch failsafe?

Thanks for explaining it.

Mike Harding
FollowupID: 371878

Follow Up By: Mad Dog (Australia) - Sunday, Jun 19, 2005 at 14:18

Sunday, Jun 19, 2005 at 14:18
As hl says below the concern is with the starting current. If we keep our leads and connections in good order the risk is minimal. With my present installation I don't bother.
FollowupID: 371881

Reply By: hl - Sunday, Jun 19, 2005 at 13:44

Sunday, Jun 19, 2005 at 13:44
The reason for the fuse in the negative line is to prevent the starting current going throught your radio if the main negative lead becomes high resistance.
If you are using an aux battery, than that is not really an issue. I have seen burned out tracks in radios where this had happened. No common, but it can happen.
I have a GU 3.0 and also had the 2.8 with various radio installations. Currently I run an Alinco DX70 and EDX-2 tuner mounted on the bull bar. This works very well, I have had no problems with the gear upsetting the vehicle electronics.
The only interference I have not fixed yet is hash from the aircon fan motor. The intercooler fan in the 2.8 also used to make a noise. Was a nice way to tell when it cut in!.
I have many leads coming out from the interior (VHF, UHF, alarm transmitter, Solar Panel). There is a big grommet on the passenger side, also one on the driver side, both allow other cables to be pulled through.
The gap in the fender near the windscreen is big enough to take RG58.
My friend's GU4 is a bit tighter with that gap, and we had trouble getting cables in.
There is no noise at all from the engine electronics at all.
AnswerID: 116370

Reply By: Willb - Sunday, Jun 19, 2005 at 15:13

Sunday, Jun 19, 2005 at 15:13
In regard to running the coax from the unit to the roof as I read it, this is all temporary, why don't you run the cable through a piece of wood or plastic that will fit between the window and the door frame when the window is wound up.
You could fit a grommet as well to stop wind and rain.

/ o \

Just a thought.
Always planning the next trip. VKS-737 mobile 1619

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AnswerID: 116378

Follow Up By: Dog (NT) - Sunday, Jun 19, 2005 at 22:15

Sunday, Jun 19, 2005 at 22:15
Thanks all...

It won't be temporary, although I will probably set it up temporary initially (going through windows etc) while I consider my options. I will mount the AH4 and Icom so that I can move them between the house and the car, but all the cable runs and antenna will be permenent in the vehicle.

Sometime this week I should have the radio and I'll add a followup on how it all goes!

FollowupID: 371956

Reply By: Hoffy - Monday, Jun 20, 2005 at 15:48

Monday, Jun 20, 2005 at 15:48
Will there be a problem with the RF getting into vechicle computer and stuffing things up either while in motion or permantly? Reading a review many years ago an SGC230 tuner, which is similair to the AH4, cooked a computer up in a European car because there was too much RF floating. I want to run my IC706 with a SG230 in my DID Pajero. I was going to mount a Squid fishing pole on the rear tyre mount for use when stationary. Apparently the problem does not exist with a resonant antenna. Would be interested in opinions also.

AnswerID: 116556

Follow Up By: hl - Monday, Jun 20, 2005 at 17:42

Monday, Jun 20, 2005 at 17:42
Hi Keith,

It will not make a difference whether you run a resonant antenna or the tuner. The only way to test is to suck it and see.
I have used a SG230 and now I have an EDX-2 on the bullbar and it works great. The advantage with this setup is when u stay somewhere for a few days you can just hang off a nice long wire or a dipole into the trees, load it up with the coupler, and Bob's your uncle.
The best time to verify compatibilty is when your truck is still under warranty. Give it the full RF treatment then, and if there is no problem... you're in the clear. If there is and the computer dies, it is best to remove the gear before you put it in for service!!!
A mate of mine ran 400 watts in a GU patrol with no ill effects.
To initially test your setup, just install and run at low power with engine running. Then increase transmit power and see if the idle speed changes. If it doesn't, you're probably ok, if it does change tread carefully.
If you ask the manufacturer, the answer will ALWAYS be no, simply because the person you ask usually does not have a clue what you are talking about and the safe option for them is to say no.
FollowupID: 372085

Follow Up By: Mad Dog (Australia) - Monday, Jun 20, 2005 at 23:32

Monday, Jun 20, 2005 at 23:32
My vehicle doesn't have a computer but at 100 HF watts the Jaycar digital voltmeter has a complete hernia while 50 watts on 2m causes it to read one volt high.
FollowupID: 372154

Follow Up By: Mike Harding - Tuesday, Jun 21, 2005 at 06:40

Tuesday, Jun 21, 2005 at 06:40
A few months ago I was camping in the High Country and had the HF set connected to my spare battery which I was also monitoring with a $25 Jayco DVM and whilst transmitting I noticed the battery had gone absolutely flat - 7V! Rats! I thought, that's stuffed the battery. Then I thought "hang on a mo...." If the battery is at 7V the set wouldn't even power up let alone transmit :)

I'll try my lab DVM at some point and see if that's affected too and if it is I'll revert to my Avo 8 which I can _guarantee_ will work :)

Mike Harding
FollowupID: 372161

Follow Up By: hl - Tuesday, Jun 21, 2005 at 06:53

Tuesday, Jun 21, 2005 at 06:53
Yes, those little Jaycar meters don't like RF. I have a thermometer/voltmeter combo and it used to "crash". I tamed it with ferrite beads on the input leads and that works to a degree. Now I have installed a switch to just turn it off when it is not required or to re-set it.
I also have the Jaycar Ameter and while that one does not crash, it can loose calibration if it is turned on an off rapidly, as in a loose connection. And it is a pain to re-calibrate in the field.
FollowupID: 372162

Reply By: angler - Monday, Jun 20, 2005 at 22:16

Monday, Jun 20, 2005 at 22:16
I have put my aerial at the rear using a mount throught the spare wheel. I ran the wiring via the rubber bung at the bottom of the well at the rear of my patrol. They are under the tail lights right at the bottom. The radio is mounted on the cargo barrier and both the aerial and radio are earthed via copper straps.
There is a picture on my web site
ick "of interest" then "lock it up".
In know the cable shown would not protect the aerial from larry light finger but you get the idea.
AnswerID: 116626

Reply By: Hoffy - Tuesday, Jun 21, 2005 at 10:40

Tuesday, Jun 21, 2005 at 10:40
Thanks to those who answered my question regaring RF getting into things. While it is still under warranty I'll suck it and see.
Keith VK4KH
AnswerID: 116666

Reply By: Dog (NT) - Tuesday, Jun 21, 2005 at 19:51

Tuesday, Jun 21, 2005 at 19:51
Hi All,

Thanks for the many reply's. My gear turned up yesterday afternoon, as you would all probably understand, all other aspects of my life have temporarily ground to a halt whilst I suround myself with cables, empty packaging, manuals (might even read those!) and other radio paraphanalia.

I will post a followup when I get around to mounting the radio!

AnswerID: 116776

Follow Up By: Mad Dog (Australia) - Tuesday, Jun 21, 2005 at 20:02

Tuesday, Jun 21, 2005 at 20:02
Exciting stuff, good luck.
FollowupID: 372257

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