HF Radio - Self Fitment

Submitted: Wednesday, Apr 02, 2003 at 15:38
ThreadID: 4183 Views:1845 Replies:8 FollowUps:7
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Have sifted through a lot of info and decided an HF radio will be my weapon of choice. Thinking mainly of a new item but by golly by jingo it is a lot folding stuff. If a 2nd hand one was considered, what are the considerations for fitting it? I've always installed my own 27megs and UHF's but they say this is a specialist job. Anyone advise just how specialist?

Miker.
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Reply By: Member - Glenn(VIC) - Wednesday, Apr 02, 2003 at 15:42

Wednesday, Apr 02, 2003 at 15:42
Miker,

Under Vehicle Requirements menu\Vehicle Set up David has explained how to install an HF radio. This may help you.Just Do It!
AnswerID: 16698

Reply By: Peter - Wednesday, Apr 02, 2003 at 16:10

Wednesday, Apr 02, 2003 at 16:10
If you have fitted 27 meg stuff then you should be OK.
Just remember check your earths
Good circuit breaker at battery for power feed.
I have heard dont run power near fridge power as causes interferance.

Peter S
AnswerID: 16699

Reply By: GaryInOz (Vic) - Wednesday, Apr 02, 2003 at 16:41

Wednesday, Apr 02, 2003 at 16:41
Just a suggestion.

If you can get your hands on some very heavy coax, use the centre conductor as the positive power lead from battery (via circuit breaker) to radio, earth the radio and the power coax braid to the vehicle at the radio, and the other end of the power coax braid to the negative terminal of the battery. This acts to shield the power supply to the radio from electrical interference. For the coax, it should be at least 0.5-0.75" diameter with a center core (braided or single core) of at least 0.125" diameter, very well tied down to resist rattling/metal fatigue of the center core, and using the minimum number and severity of bends in the coax.

Not really sure if this works or is needed for HF, but it works a treat on microwave links (similar to the old Channel 10 "Live Eye" vans)
AnswerID: 16701

Follow Up By: joc45 - Wednesday, Apr 02, 2003 at 17:59

Wednesday, Apr 02, 2003 at 17:59
Use of coax for a power feed is a waste, and unless it is VERY large coax; ie, larger than RG213, it still won't carry the current >20A for the HF unit. Use at least 10 sq mm cable, pref run directly from the batt via a fuse or circuit breaker. As earlier said, avoid using the same feed as the fridge - the extra drain will drop the volts more, and you will get a hum or buzz on your transmitted audio.
You may need suppressor capacitors on the dc feed, and if you have a petrol vehicle, you may need to suppress the HT interference. Alternators can make noise, and a coaxial suppressor is better than the usual one with a single lead hanging out. If you have a diode combiner for your aux battery, this can generate commutation noise, and capacitors across the diodes may help.
As far as antenna cable is concerned, 0.5-0.75" coax might be fine, and indeed necessary for microwave installations, it is really impracticable and unnecessary for the frequencies involved with HF. Type RG58 is the common 1/4" 50 ohm coax, and will work fine for the frequency and cable lengths we are using here. Coax with foam or cell insulation has less loss, but is easily crushed, and is not a good idea for vehicle installs. Plain RG58 has a solid insulation.
Both the antenna mount and the radio need to be RF-earthed; a heavy braided cable should be run from the device frame to the body, and kept as short as possible.
Again, refer to David's install notes.
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FollowupID: 10339

Follow Up By: Gordon - Wednesday, Apr 02, 2003 at 18:05

Wednesday, Apr 02, 2003 at 18:05
GaryInOz(Vic)
I know where you're coming from, but that's not necessary. My HF works fine with a single pair (+and -), heavy-duty, double-insulated, multi-stranded-automotive cable and the bonus is that it's very easy to run compared with your 1/2 inch coax. I have never heard of anyone having a problem that has required coax to fix. I'm not a leccy but you might know - do the fields from a (+ and -) pair cancel to some extent? PS I know they wouldn't cancel as well as your coax.
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FollowupID: 10341

Follow Up By: GaryInOz (Vic) - Wednesday, Apr 02, 2003 at 19:12

Wednesday, Apr 02, 2003 at 19:12
Thanks for the feedback guys, the microwave Txer was a 500 milliwatt that required 24 volts up a 20' pneumatic telescopic mast, only needed about 6-7 amps (yes, VERY inefficient Txer!). As I said, I wasn't sure it would necessarily be relevant.

In answer to Gordon, yes, as long as they are twisted together over the entire length from battery to radio, although the effect is only apparent for rf frequencies, ie. stops your UHF or 27 MHz rig from interfering with the HF, but is not so effective against ignition/fuel pump/fridge noise. Unfortunately running two (+ and -) power leads can also lead to double the voltage drop losses in the cables under heavy current compared with using a solid earth at the radio and battery, and therefore result in a slight decrease in power output.
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FollowupID: 10344

Reply By: Gordon - Wednesday, Apr 02, 2003 at 17:43

Wednesday, Apr 02, 2003 at 17:43
MikeR
Last year, I bought a second hand Codan 8528 for $1,100 ($3,000 new) and auto-tune aerial for $600 ($1,500 new) and paid $100 for expert help. So you can see there can be a big saving - I got a unit worth $4,500 new for under $2,000. Of course my unit is not new, it has no warranty, and it will become obsolete (i.e. difficulty getting parts) sooner than the latest model - but it works fine and should see me through. I mounted all components (transmitter, aerial, remote head) and ran all the cables. You will need an expert to program your frequencies and strictly speaking that expert will need to verify that you are entitled to use those frequencies. You will need ACA license to access Flying Doctor frequencies and VKS737 or other HF club membership for their frequencies. The power and aerial cables carry very high currents, so if you don't know what you're doing then get expert help. You dont want a fire or interference with other electrical equipment !!! My tips - No kinks, keep power supply cable separate from aerial and control cables as much as possible, install a fusible link close to the battery, have good heavy duty earths and run a separate heavy duty power supply (+ and -) direct from your auxiliary battery. If you mount the aerial on the bull bar then don't run the cable through the grill as I did because it is then more difficult to fit a radiator blind for deep water crossings. Instead run cables up from underneath the grill. You will need to remove the aerial cable connectors with a soldering iron (in order to feed the cables through tight gaps and through the firewall) and re-solder after installing the cables. Note the pin connections for each coloured wire on the control cable connector. Run the cables backwards from the front of the vehicle through the firewall because the connectors at the aerial end are more difficult to remove. Mount the transmitter high enough inside the vehicle so that it wouldn't be submerged if you stall in a deep water crossing otherwise you will have to remove the transmitter before entering the water. I mounted mine behind the backrest of one of the rear seats using short self tappers so they don't go through the seat padding - it's out of the way and I ran the cables so as not to inhibit folding the backrest or seat hob, but its still very easy to access the transmitter by folding the backrest forward. I made a bracket for the control head and mounted it centrally just above the gearbox / transmission tunnel in front of the gear lever (80 Series) - it's out of the way but very handy and easy to see the illuminated LCD face. I took my time to think things through before installing because there are a lot of factors to consider. Even then I made some mistakes like initially mounting the transmitter under the passenger seat before I realised that it could be easily flooded and was difficult to access). It was not a quick job but mainly because i am a bit fussy. If you're fussy like me then do it yourself but don't be in a hurry. The alternative is to entrust the job to others but they don't know how you like to load your vehicle or what ompromises you're willing to make, so you may go through a few iterations before you're satisfied. The transmitter does take up a bit of room and it needs to be reasonably accessible because it needs to be removed for any frequency changes or if you want to protect it from theft when not in use. Good luck. (If I can help further email me gordon.buck@originenergy.com.au).
AnswerID: 16704

Reply By: Gordon - Wednesday, Apr 02, 2003 at 18:30

Wednesday, Apr 02, 2003 at 18:30
MikeR
Just one more tip - you might not want 27Meg or UHF now but they are functional and entertaining when travelling with others and to pass the time on long trips. Plan for future installation of either or (like me) both as well as your HF. HF is great for emergencies but you can't beat UHF for car to car, some people have 27 Meg instead of UHF so, for another $130 bucks you can talk to anyone. My UHF and 27 Meg are mounted out of the way but handy in a visor shelf - one each side.
AnswerID: 16712

Reply By: PETER - Wednesday, Apr 02, 2003 at 23:03

Wednesday, Apr 02, 2003 at 23:03
dont know where you are but if in victoria contact alex dawes at heathcote victor 344 he is a private person with excellent prices on secondhand sets and instalation is second to none. regards peter
AnswerID: 16745

Reply By: miker - Thursday, Apr 03, 2003 at 11:33

Thursday, Apr 03, 2003 at 11:33
Thanks for all the replys and info. I did discover David's fitting intructions after I posted, very informative. Gordon, you hit the nail on the head. I'm more than a touch fastidious when it comes to this sort of thing and experience (very recent, ARB #@*#%#$) tells me no one ever cares for work on one's chariot like the owner. There are so many "little" things that can be done to make a good job and just as many "little" shortcuts. My gut feel is to buy new but do the installation for the aforementioned reasons more so than to save $200 (still good). However I'll enquire further with regard to the tuning aspects. It's a bullbar mount on a Defender Xtreme. Box will go on the cargo barrier, head I'm not sure yet.

Cheers
Miker.
AnswerID: 16770

Follow Up By: miker - Thursday, Apr 03, 2003 at 11:45

Thursday, Apr 03, 2003 at 11:45
Thanks for all the replys and info. I did discover David's fitting intructions after I posted, very informative. Gordon, you hit the nail on the head. I'm more than a touch fastidious when it comes to this sort of thing and experience (very recent, ARB #@*#%#$) tells me no one ever cares for work on one's chariot like the owner. There are so many "little" things that can be done to make a good job and just as many "little" shortcuts. My gut feel is to buy new but do the installation for the aforementioned reasons more so than to save $200 (still good). However I'll enquire further with regard to the tuning aspects. It's a bullbar mount on a Defender Xtreme. Box will go on the cargo barrier, head I'm not sure yet.

Cheers
Miker.
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FollowupID: 10380

Reply By: Member - Peter- Thursday, Apr 03, 2003 at 22:35

Thursday, Apr 03, 2003 at 22:35
Mike
I have installed HF's for about 15 years now, most of the advice given is good, as someone said check earths especially bullbars to chassis to body, remove bolts, grind/scrape paint etc off until shiny and reinstall the bolts, will save you heaps of grief down the track.
I see you have a Defender, if it has a TD5 engine forget about using the HF while the engine is going, the receiver will be swamped by the electrical noise/interference from the injection system and it is nigh on impossible to shield/screen it out.
Another tip, connect the HF to the main battery if you have a dual battery system, HF radios with autotune antennas will not tune if the volts are down after a day running the frig, lights etc if you aren't travelling. Unless you are going to be on the radio all day you will never drain enough to stop the vehicle starting. My longest stop in one spot without starting the truck was a week, I used the HF every day to call in on the sked and it was scanning from dawn to dusk every day, the diesel troopy fired up straight away when it was time to hit the road again.
Another important point is to NEVER connect the negative/ground lead from the HF (or anything else for that matter) directly to the negative terminal of the battery. Always connect it to the vehicle end of the negative lead or very close to it.
The reason for this is that if the main vehicle negative lead becomes loose or comes off guess where the starting current flows, yes that's right through your HF radio. Believe me the HF is totalled if this happens and I've seen quite a few over the years.
Peter
AnswerID: 16833

Follow Up By: Rob - Friday, Apr 04, 2003 at 11:34

Friday, Apr 04, 2003 at 11:34
Peter.

Good points. I'm trying to work out the reason for your last point.
Why would the HF be damaged if the main -ve lead comes off?

I can see that if the HF main unit is earthed at the case, then the
starting current would flow back through this earth strap and then
along the HF -ve return wire. This could cause sudden heating & fire.

Would the actual HF unit be damaged & if so - why? You are the second person I heard this from & I'm trying to work it out!

Many thanks

Rob
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FollowupID: 10452

Follow Up By: Member - Peter- Friday, Apr 04, 2003 at 18:01

Friday, Apr 04, 2003 at 18:01
Rob
The reason is that while the case of the transmitter is earthed, the negative (black lead on the power cable) is actually connected direct to the inside of the unit/transmitter to avoid voltage drops.
So the actual transmitter circuitry is carrying the load, exit one PCB if it happens, believe me it will be beyond repair, the inside of a HF radio is not meant to carry any sort of starting/cranking current for your average 4wd.l
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FollowupID: 10488

Follow Up By: miker - Monday, Apr 07, 2003 at 08:13

Monday, Apr 07, 2003 at 08:13
Good stuff - thanks guys. I'm no "techno" or sparky for that matter but understand the feedback. Should be a bit of fun next Saturday! Catch you in the bush.

Miker.
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FollowupID: 10611

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