HF Radio location in cab?

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27 Jun 2013 16:10 #1 by Alister McBride
Alister McBride created the topic: HF Radio location in cab?
Hi all,
I've just started a long trip and in the hurry before we left i decided to install the HF radio on the way. Looking at possible locations though i think it would be much easier to install it in the dualcab module so I can only use it in the rear of the vehicle. My theory being that from what i can understand, use of a HF seems to always be while stationary and so it wouldn't matter about location...? In fact a lot of people just seem to put the antenna up when they need to use it...
Any input would be appreciated as i don't know much when it comes to using HF's.
Cheers, Alister

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27 Jun 2013 19:35 #2 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: HF Radio location in cab?
In a previous life I used to install Codan and Barrett HF's in all sorts of vehicles and boats.
In the "old" days before vehicles gained much in the way of electronics we always used them on the go as there was little interference from the vehicle. As time went on though the increased electronics led to increased interference with some vehicles being impossible to screen so if the engine was on the HF was off!
I've not put one in an Oka for many years but from memory they were pretty good interference wise but modern accessories like GPS, TPMS etc all create interference of varying degrees. I'd reckon solar controllers, regulators and the like would all cause problems.
One of the main reasons I've not put my Barrett in 374. Easier to cart the satphone.
In Oka's I used to mount the main transmitter behind the drivers seat so that it could be reached from the rear and when the remote control heads came into vogue put them on the dash on the passengers side towards the centre.
Antenna's of course on the existing bullbar mount.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

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27 Jun 2013 22:54 - 28 Jun 2013 06:56 #3 by dandjcr
dandjcr replied the topic: HF Radio location in cab?
Alister, unlike CB which can be useful for close range comms at any time, HF radio is primarily a long range communications medium which is dependant on propagation characteristics, which are usually better from dusk till morning. (VKS skeds are all in the late afternoon and early morning for this reason, and well worth listening/contributing to).

But this means few people will be using HF during the day so having the radio accessible from the cab while driving is not that useful. Also a bullbar antennae, which are quite large, would need to be raised while moving and subject to vibration and damage.

HF comms is certainly possible during the day and will be better on higher frequencies (for emergency selcall contacts, not many travellers will be listening then), but I think the best arrangement is to have the radio in the rear cab and use it when stationary in the evening/morning when it's easier to erect a tall antenna.

But as Peter says, HF reception is very sensitive to electrical interference from computers, inverters, fan speed controllers, battery chargers, nearby power lines, generator ignition etc., in fact almost any electronic equipment. HF radios have very sensitive receivers so electrical noise affects reception of weak signals (micro-watts) but not transmission (up to 100 watts), so even if you can't hear a signal, there's a good chance that an emergency transmission would still be received. You'll quickly learn what's causing noise by progressively switching things off with the radio on.

The practical considerations of locating an HF radio are proximity to a solid 12v 20amp supply (preferably the starter battery so you have power available for emergency calls) and as short an antenna lead as practical from the radio to the antenna/bullbar. The radio case and bullbar should also be effectively grounded to the vehicle chassis/body with a separate grounding wire.

Although radios usually have impressive looking heat sink fins, they don't actually get very warm since they only consume significant current during transmission (it's proportional to how loud you talk) so they can be tucked away in a cupboard as long as you can still access the front panel easily.

David and Janet Ribbans - Oka 148
Oka148 profile here.
Visit our technical and travel blogs: here.
Last Edit: 28 Jun 2013 06:56 by dandjcr.

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29 Jun 2013 18:08 #4 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: HF Radio location in cab?
As David said connect it to the starting battery so that power is available if the aux is flattened at all.
NEVER connect the negative ground for the HF to the negative on the battery rather at the other end on the chassis/body.
The reason for this is that if the main ground lead for the starter becomes loose or adrift the starting current will take the path of least resistance which can be through you expensive HF radio. They don't work after such treatment and usually require total replacement. I've had to break that bad news to a few owners over the years.
You could fuse both positive and negative legs but that just introduces another possible poor connection/failure point, best to just avoid connecting it to the negative of the battery.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 1100w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

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01 Jul 2013 19:49 #5 by Dean and Kaye Howells
Dean and Kaye Howells replied the topic: HF Radio location in cab?
Hi Alister, We're in the same boat (nearly) with the deadline for holiday departure approaching and the HF not yet installed. A bit of a quandary really, I've got a remote head Codan 9323 with autotune antenna and a Barrett 250 (non remote head) with a Terlin multitap antenna and base. The Codan's the better set but the auto tune antenna is pretty big and I'm not really happy with it sitting out front on the bulbar and spoiling the view. The Barrett is easier to install and has a less intrusive antenna. I'm with Peter here I'll mount the main unit behind the drivers seat. If I fit the remote head unit I'll put the remote head and speaker (facing the driver) under the shelf I've built that goes from the roof mounted centre aircon unit to the passenger side. This makes it accessable from the drivers seat and the rear of the OKA as well.

I've made a mount for the Codan autotune antenna that puts its base 700mm above the rear RH corner bumper with the whip base about level with the roof. Don't know how effective it will be but it's better than at the front. As time runs out I havn't decided which way I'll go.

There are still some QMac 50 watt HF sets out there which are quite small and would fit well in the LT dash where the silly clock goes. The later version of these sets are very good with the export version highly sought after.

Deano

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03 Jul 2013 12:05 #6 by dandjcr
dandjcr replied the topic: HF Radio location in cab?

Dean and Kaye Howells wrote: I've made a mount for the Codan autotune antenna that puts its base 700mm above the rear RH corner bumper with the whip base about level with the roof. Don't know how effective it will be but it's better than at the front.
Deano


Deano, as long as the mount doesn't vibrate too much and is effectively grounded to the Oka chassis/body, that location will be fine. The whip will be above the Oka which is where it will work best, and the Oka roof acts as a nice ground plane to get the signal into the air. The whip might get attacked by branches though.

David and Janet Ribbans - Oka 148
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03 Jul 2013 16:33 - 03 Jul 2013 16:41 #7 by Dean and Kaye Howells
Dean and Kaye Howells replied the topic: HF Radio location in cab?
Here's a pic of the antenna mount (if I can work out how to upload it). The mount shouldn't vibrate much as it's 50mm square 6mm wall thickness with a 6mm top plate and gusseted to with an inch of its life. It may double as a spare wheel carrier mount at a later date so it was made quite sturdy.




The roof rack may detract from the antennas efficiency but I wasn't game to make it any higher, but it is on the drivers side so should miss most trees etc.

I wasn't happy to have it on the bull bar as I thought this was too prone to damage, especially on the passenger side. "You're not putting that bloody thing on my side" said Kaye who is wont to take photos through the windscreen whilst travelling and it's far too intrusive to mount on the drivers side. So this is plan 'c' so to speak.

Deano :)
Last Edit: 03 Jul 2013 16:41 by Dean and Kaye Howells.

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03 Jul 2013 17:17 - 03 Jul 2013 17:19 #8 by OKABloke
OKABloke replied the topic: HF Radio location in cab?
A HF Antenna needs clearance around the antenna to work.


In the Up Position


Travel Position, Just add the Whip before erecting.[/size]

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Last Edit: 03 Jul 2013 17:19 by OKABloke.

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03 Jul 2013 17:28 #9 by Joseph Baz
Joseph Baz replied the topic: HF Radio location in cab?
Please excuse my ignorance in this topic,I have a Codan left over from my Halls Creek days and I'm wandering wether or not is worth installing the unit as I been told that a satellite phone is all you need, can some one explain the pros and cons
Cheers,Joe

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03 Jul 2013 18:26 - 03 Jul 2013 18:31 #10 by dandjcr
dandjcr replied the topic: HF Radio location in cab?

Dean and Kaye Howells wrote: The roof rack may detract from the antennas efficiency but I wasn't game to make it any higher, but it is on the drivers side so should miss most trees etc.
Deano :)


Deano, the roof rack won't make much difference to antenna efficiency, it would have to be completely surrounded by conducting material (like a Faraday cage) to make a significant impact, but it could affect it's directional performance (better in one direction than another).

Higher would be better but there are plenty of examples of similar rear antenna mounts, eg this Kaymar mounting .

Barett's preferred and acceptable locations are here:



Antenna performance is very subjective and there is no perfect or completely wrong location, even lying on the ground works. I recently got a perfect reception report from Alice Springs (in Adelaide) with my antenna lying on a wheelie bin.

Don't forget to carry a 9m length of insulated wire as a good emergency antenna. Just connect it to the antenna lead and chuck it as high as you can make it into a tree or over a bush, or just lay it on the ground in the general direction of the required transmission. Most radios have a transmit light which glows while talking, the brighter it is the better your radio/antenna is working.

Unfortunately auto tune antennae are not as efficient as a tall vertical whip antenna would be (and a tapped whip is somewhere in between) but they are convenient for selecting different channels.

David and Janet Ribbans - Oka 148
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Last Edit: 03 Jul 2013 18:31 by dandjcr.

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03 Jul 2013 18:59 #11 by dandjcr
dandjcr replied the topic: HF Radio location in cab?

Joseph Baz wrote: Please excuse my ignorance in this topic,I have a Codan left over from my Halls Creek days and I'm wandering wether or not is worth installing the unit as I been told that a satellite phone is all you need, can some one explain the pros and cons
Cheers,Joe


Joe, I'm totally biased of course, never having used a sat phone, but I wrote some notes on the benefits of HF radio in a recent newsletter , page 6.

Ignoring the obvious phone/HF radio physical differences, the deciding factor for me is the the ability to contact many, rather than just one listener. If I had a real emergency I would want as many people to know about it as possible, and help (certainly advice) might be just around the corner.

Atmospheric conditions do sometimes makes radio communications difficult, but I've also seen sat phone users experience difficulties in making satellite contact. So an EPIRB is essential too.

David and Janet Ribbans - Oka 148
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04 Jul 2013 07:40 - 04 Jul 2013 07:41 #12 by Dean and Kaye Howells
Dean and Kaye Howells replied the topic: HF Radio location in cab?

dandjcr wrote:
Don't forget to carry a 9m length of insulated wire as a good emergency antenna. Just connect it to the antenna lead and chuck it as high as you can make it into a tree or over a bush, or just lay it on the ground in the general direction of the required transmission. Most radios have a transmit light which glows while talking, the brighter it is the better your radio/antenna is working.

Unfortunately auto tune antennae are not as efficient as a tall vertical whip antenna would be (and a tapped whip is somewhere in between) but they are convenient for selecting different channels.



Thanks, I've got a 6 metre telescopic pole and several antenna tuners (one with built in balun), plenty of wire and a Terlin multi-tap antenna to chose from for my plan 'b' antenna. I'll also have a coax fed balun/long wire antenna to chose from if it arrives in time.

Most non ham HF sets don't have built in antenna tuners so I'd expect a pretty ordinary match with a long wire on the ground/bush/tree and I'm a bit leery of 100 watts of RF just 'lying around' so to speak. But certainly better than nothing in an emergency and quite fine for receiving.

As for the auto tune Codan 9350 antenna, a SWR of 1.2:1 on 8022 kHz which I thought was OK when mounted on the front of the OKA.

Joe, if you've got the Codan (which model ?) it certainly won't hurt to install and where as the sat phone lets you talk to one person at a time (if you know who to ring and have the number), the HF allows greater interaction with other travellers and base stations as well as weather/road reports. VKS 737 is also able to pass along messages. As long the HF has 8022 & 5455 kHz it'll be fine.

Deano :)
Last Edit: 04 Jul 2013 07:41 by Dean and Kaye Howells.

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04 Jul 2013 08:16 #13 by dandjcr
dandjcr replied the topic: HF Radio location in cab?

Dean and Kaye Howells wrote: Joe, as long the HF has 8022 & 5455 kHz it'll be fine.


Joe, most old Codans don't have VKS channel frequencies fitted but they can usually be modified, depending on the model (6801, 7727, 8727's are OK and are quite reliable). I've upgraded several Codans to include 5455 and 8022 khz (the primary VKS channels 1 and 2) and also fitted selcall microphones so they have all the current emergency features required.

If you are interested in going that way, I can certainly help.

Regards,

David and Janet Ribbans - Oka 148
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04 Jul 2013 08:28 #14 by dandjcr
dandjcr replied the topic: HF Radio location in cab?

Dean and Kaye Howells wrote: As for the auto tune Codan 9350 antenna, a SWR of 1.2:1 on 8022 kHz which I thought was OK when mounted on the front of the OKA.
Deano :)


Deano, if you can achieve an SWR of 2 or less when mounted on the rear you doing OK (less than 10% power loss). Above 2 to 2.5 and you are losing 20-25% or more of your transmit power , 3 or higher is bad.

An insulated antenna lying on the ground is OK as long as no one touches it while actually transmitting (talking). The same applies to any antennae mounted on a bullbar. Not likely to be fatal but could deliver a mild shock.

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04 Jul 2013 09:13 #15 by OKA 138
OKA 138 replied the topic: HF Radio location in cab?
Joe I can attest to Davids skill in resurrecting old Codans , mine had been gathering dust in the shed for 10 years or so and it is now working as good as ever with full selcall facilities.
We also have a sat phone but as the VKS network handle all the RFDS radio traffic it made sense to go the radio way again , with the numbers of people now using the VKS network help could be only a few minutes away which wouldn't happen with a sat phone unless you had their number.
We still use the sat phone but mainly for keeping in touch with the family.

Cheers Dave

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05 Jul 2013 19:13 #16 by Joseph Baz
Joseph Baz replied the topic: HF Radio location in cab?
Thank you all,the radio is up to date with frequencies,it was upgraded by Terlin a couple of years ago also I have been a member of VKS for a while now,it certainly is a more sociable medium as I remember the daily roll call from the Derby and Whyndam RFD bases and always felt a degree of safety travelling alone in the middle of nowhere,will definetly look for a fitting spot in the cab
Cheers,Joe

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05 Jul 2013 19:26 #17 by Joseph Baz
Joseph Baz replied the topic: HF Radio location in cab?
Thank you all,the radio is up to date with frequencies,it was upgraded by Terlin a couple of years ago also I have been a member of VKS for a while now,it certainly is a more sociable medium as I remember the daily roll call from the Derby and Whyndam RFD bases and always felt a degree of safety travelling alone in the middle of nowhere,will definetly look for a fitting spot in the cab
Cheers,Joe

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05 Jul 2013 19:26 - 05 Jul 2013 22:49 #18 by Joseph Baz
Joseph Baz replied the topic: HF Radio location in cab?
Thank you all,the radio is up to date with frequencies,it was upgraded by Terlin a couple of years ago also I have been a member of VKS for a while now,it certainly is a more sociable medium as I remember the daily roll call from the Derby and Whyndam RFD bases and always felt a degree of safety travelling alone in the middle of nowhere,will definitely look for a fitting spot in the cab
Cheers,Joe
Last Edit: 05 Jul 2013 22:49 by Joseph Baz.

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07 Jul 2013 16:13 #19 by Alister McBride
Alister McBride replied the topic: HF Radio location in cab?
Thanks for the input all! The radio is snuggly installed behind the rear seat of the dual cab with head unit just above the rear seat. Yet to do the electricals but there's the compressor in the same spot opposite so have a good power supply right there and is earther on the chassis (i'll make sure the compressor is off during com's!).
I'm just deciding which radio network to go with at the moment and trying to decide between VKS and HF Radio Club. I'll do a bit more research and go from there.
Cheers again!
Alister

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08 Jul 2013 07:01 - 08 Jul 2013 18:09 #20 by dandjcr
dandjcr replied the topic: HF Radio location in cab?
Alister, you could listen in to the various eastern and central VKS base skeds on 8022 Khz in the mornings (7.30 to 9am AEST) and/or evenings (4 to 6.30pm) to see how they do things. Might help you decide. WA base skeds are later.

Listening in doesn't require membership but transmitting does (membership covers licence fees). You might consider joining both clubs for a year ($110+ pa each). Pro rata is less, right now you could join both for the rest of this year for $50-65 each before deciding which one to stick with. Check that your radio (and antenna) can access their main frequencies before joining.

A useful list of frequencies for all HF radio clubs is here .

Note, for anyone whose radio doesn't have selcall facilities (needed these days to contact the RFDS/base operators by radio), there are now apps for iPhone, Android, Mac and PC computers to generate (but not decode) selcall tones. See this site for details. You key in the required selcall number, press the radio mike PTT button and hold it near the phone/computer speaker. Cheap and useful in an emergency. Once contact has been established, radio comms takes over as normal.

Selcall app update: See this VKS document .

David and Janet Ribbans - Oka 148
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Last Edit: 08 Jul 2013 18:09 by dandjcr.

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