Emergency aerial for Barrett 950 HF radio

Submitted: Wednesday, Feb 25, 2004 at 21:19
ThreadID: 10791 Views:4492 Replies:10 FollowUps:14
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Ok, in the event of a rollover, I might bust the autotune and need something else for an aerial.

Q1 How do you make a wire aerial for say 8022? What gauge wire, how long and how do you hook it up to the set? Do you have to earth anything?

Q2 I gather it is possible to hook one of these up to a working autotune so you can increase range on all frequencies (when a big tree is available!). How is this done?

Thanks,
Phil
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Reply By: Wayne (NSW) - Wednesday, Feb 25, 2004 at 21:58

Wednesday, Feb 25, 2004 at 21:58
Using your Sat phone and ring Barrett Communications Free call 1800 999 580 and they should be able to help.

Only joking about the phone but a good point about the aerial.
How much power does the HF radios use? Could you flattern the battery if left on over night by mistake.

WayneAlways Out'N About
AnswerID: 48102

Follow Up By: Phil G - Wednesday, Feb 25, 2004 at 23:09

Wednesday, Feb 25, 2004 at 23:09
Wayne,

They use a heap when transmitting (125 watts), but very little when you're just listening. I must measure mine out of curiosity.
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FollowupID: 310039

Follow Up By: Greg Harewood - Thursday, Feb 26, 2004 at 22:45

Thursday, Feb 26, 2004 at 22:45
Good point ..If I roll my car and destroy the Sat Phone what HF frequency can I contact the sat phone company on:)
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FollowupID: 310165

Reply By: Mad Dog Morgan (Geelong) - Wednesday, Feb 25, 2004 at 22:19

Wednesday, Feb 25, 2004 at 22:19
Phil, I think most of this has be covered in thread 10299. The wire gauge doesn't matter too much as long as it's thick enough to avoid overheating. I used telephone wire once with the 4 conductors twisted together, worked ok for a short contact.
I'm not familiar with how the autotune mounts but you'll need to get the wire antenna connected to the centre conductor of the base. The existing earth from the base to vehicle is used. The other method which is a bit more complex is using a half wave dipole and feeding half of the antenna with the centre conductor and the other half with the braid at the center.Two supports are required, you'll need a length of coax to run from the radio up to the middle of the antenna where an insulator is used to seperate the two halves. Oh yeah, each half is a 1/4 wave length. BEAM ME UP SCOTTY


Hooroo
Ray
AnswerID: 48107

Reply By: Nudenut - Wednesday, Feb 25, 2004 at 22:22

Wednesday, Feb 25, 2004 at 22:22
q1
a long wire is should work but i need more info on how to work out how to do it...have to consult a ham enthusiast I reckon.
Q2
using a long wire i dont think you need ant thing else. A long wire can be extrodianary lengths I beleive.

Help me Ham enthusiast..i have always wondered?I am human ...I think?
Must be....make too many mistakes!
AnswerID: 48111

Follow Up By: Mad Dog Morgan (Geelong) - Wednesday, Feb 25, 2004 at 22:59

Wednesday, Feb 25, 2004 at 22:59
Yeah a long wire works and should be multiple wave lengths long but it has to be fed correctly. Transmitters expect to see a load impedeance close to 50 ohms, too far away and modern transmitters fold back the power to avoid damage. The way to acheive this with a long wire is by using an antenna tuner either manual or automatic. BEAM ME UP SCOTTY


Hooroo
Ray
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FollowupID: 310036

Reply By: Member - Bob L - Wednesday, Feb 25, 2004 at 22:57

Wednesday, Feb 25, 2004 at 22:57
Phil
Just been diving through my antenna theory handbooks.
A simple 1/2 wave dipole would get you out of trouble but you would need a separate set of elements for each frequency.
The length of a half wave in free space is-
Length (ft) = 492 divided by f (frequency in Mhz) . In practice substitute the figure 492 by 468 which is 95% of same.
Use 50 ohm coax (RG58) ,any length, to feed the center point of the above length of wire ie centre wire to one side and braid to the other, You could use an old CB SWR meter to fine tune the final length in need . Support each end with nylon rope as an insulator as high and horizontal as reasonably possible.
If you choose the correct frequency for the time of day you can work anyone with this set up.(probably got more gain than an auto tuning whip)
NOTE , even a dipole can be directional so a little antenna theory might not go astray,
try a search of some of the amateur radio sites.
If you need more info or want to confirm calculations drop me a line.

PS If you cut a length of 4t wiring cable to half of the calculated figure (1/4 wave) then split it, you will end up with the correct length which will handle 100 watts easy,just dont stand too close.

Cheers
Bob L

.
AnswerID: 48117

Follow Up By: Topcat (WA) - Thursday, Feb 26, 2004 at 00:20

Thursday, Feb 26, 2004 at 00:20
I concur with Bob on the aerial setup & wire length calculations for 1/2 wave, however I would recommend using a horizontal aerial setup of 1/4 wavelentgh because it is more efficient in transmitting the signal. Horizontal antennas radiate in all directions except along the line of the wire. Vertical dipoles of 1/2 wavelength radiate most of their radio waves sideways rather than vertically & because they are so short, they are very inefficient in converting radio power into radio waves.
I carry a couple of long wire horizontal antennas setup for RFDS frequencies which I attach to a couple of star pickets which I carry as ground anchors for winching. I just use egg insulators (available from Dick Smith stores)between each end of the wires (standard 2mil hook-up wire) & the star pickets & run 50 ohm coax from the aerial to the radio. The calculation for 1/4 wave wire lengths is:- length in meters X 71.49 = frequency in Megahertz.
I have used this successfully & transmitted to a RFDS base station over 2000km distance. If you want more details of setting it up give me your email address & I'll send you a wire length chart & details on set-up. Cheers.
Have Wheels Will Travel
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FollowupID: 310049

Follow Up By: Topcat (WA) - Thursday, Feb 26, 2004 at 00:30

Thursday, Feb 26, 2004 at 00:30
Correction to wire length calculation. Should read :
length in meters = 71.49 divided by frequency (Megahertz) So for 8020 you will need 8.91 meters of wire for a horizontal aerial setup.Have Wheels Will Travel
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FollowupID: 310052

Follow Up By: Mad Dog Morgan (Geelong) - Thursday, Feb 26, 2004 at 00:44

Thursday, Feb 26, 2004 at 00:44
Have a look at the diagram here Phil for two simple antennas the diople and inverted v, also there's a calculator for working out the lengths. You'll sometimes see slightly different formulas for working out the lengths don't be concerned as people have slightly different theorys about this. The idea is to get you in the ball park. As Bob mentioned all antennas should be tuned with an SWR (standing wave ratio) meter as every installation is different.

http://www.hamuniverse.com/dipivcal.html BEAM ME UP SCOTTY


Hooroo
Ray
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Follow Up By: Mad Dog Morgan (Geelong) - Thursday, Feb 26, 2004 at 00:50

Thursday, Feb 26, 2004 at 00:50
oh and by the way you will read in places that you need a balun to feed a dipole and strictly speaking you do but it'll work just fine without it with a bit of radiation from the coax.
A balun converts the unbalanced coax cable to suit the balanced antenna. BEAM ME UP SCOTTY


Hooroo
Ray
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FollowupID: 310054

Follow Up By: Topcat (WA) - Thursday, Feb 26, 2004 at 03:01

Thursday, Feb 26, 2004 at 03:01
Mad Dog it looks simple enough if you have got a long enough centre pole to carry around with you (maybe telescopic) but two 1 meter poles some 17 odd meters apart will do the same trick if you haven't a tree in the vacinity to use. I see you are a HAM man. Used to run a six meter setup in the early sixties. Cheers.Have Wheels Will Travel
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FollowupID: 310061

Follow Up By: Mad Dog Morgan (Geelong) - Thursday, Feb 26, 2004 at 09:59

Thursday, Feb 26, 2004 at 09:59
Topcat, I got my ham ticket as a young fella in 79 and spend years chasing DX so I don't get too excited about an antenna 1 metre high but I guess it's ok for the short distance stuff around Oz but when conditions are difficult height is King. I Iook at thing differently to most as radio is a hobby for me. Yeah 6 metres is a great band, commonly refered to as the "magic band" BEAM ME UP SCOTTY


Hooroo
Ray
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FollowupID: 310073

Reply By: Member - Raymond - Thursday, Feb 26, 2004 at 08:23

Thursday, Feb 26, 2004 at 08:23
Hi Phil
The easy solution is what I do which is carry a long wire which I can use in an emergency or if the signal from the Autotune is not good enough.
The Unit I use is from Bushcomm Pty Ltd
akes just a few minutes to set up and can be used on all frequencies. The radio will show that it does not autotune, but from Barrett it is fine to use it and transmit.
The radio uses very little power on receive, so leaving it on all night is not a problem. Even though they use a lot on transmit, these are normally short periods of time
Regards Ray VKS737wanderin' in retirement. victor 2010
AnswerID: 48154

Reply By: The Banjo - Thursday, Feb 26, 2004 at 08:30

Thursday, Feb 26, 2004 at 08:30
To boost my 950 performance (if needed) while static, I run a wire off the top of the autotune out to an elevated point. My length is 9323mm (1/4 of 8022khz) - As Topcat says, he has a diff formula (for speed of light in metal -mine is in a vacuum - might be a good point). 9323 works well for me. Far as I'm told (seems others suggest this too), if the autotune was ripped off, you'd need to get the centre coax wire onto the long wire and the outer shield earthed onto the body (with some worthwhie insulation - seperation) - if you have a short you cook the radio gizzards - if you don't earth the outer, you don't get signal. With a bit of insulation tape, olfa knife and some pliers, you should be away. Anyway, I've hung onto my Uniden 27 meg SSB as a backup for such circumstances.I need red sand under me.
AnswerID: 48156

Reply By: Peter - Thursday, Feb 26, 2004 at 11:43

Thursday, Feb 26, 2004 at 11:43
I carry a long length of Figure 8 wire.

I broke the stainless steel whip and just connected a piece of insulated wire to top of auto tune It was about 2.2 m long. tied this off to poat andit worked a treat.

Here is an extract on emergency aerials

There may be occasions when damage to a whip antenna, distance, or topography
makes communications difficult or non-existent. In such cases a wire antenna
can be constructed which will, in most cases re-establish communications.

The length of the antenna has a direct relation to the frequency of operation
therefore the wire must be cut to the correct length. The following formula
will give the length of an emergency wire antenna.

Length in metres = 71.25/Frequency (in MHz)

e.g. 71.25/3.995 MHz (3995kHz) = 17.84 metres.

Length in feet = 234/Frequency (in MHz)

e.g. 234/3.995MHz (3995kHz) = 58.57 feet.

The length of wire required for VKS - 737 frequencies is as follows:

Frequency Metres Feet
3995kHz 17.84 58.57
5455kHz 13.06 42.90
8022kHz 8.88 29.17
11612kHz 6.14 20.15
14977kHz 4.76 15.62

If insulators are used, the length is measured from the hole in the insulator
through which the antenna wire goes. Therefore, the wire must be cut longer
than the calculated length to allow for insulator wrap around.

Obtain some copper wire (preferably plastic coated) and cut it longer than
the length calculated for the frequency. Attach an insulator
(nylon rope will do) to one end of the wire so that the distance between the
hole and the end of the wire is the correct length.

Attach a length of rope and a weight to the end of the rope with the insulator
on, throw it over a tree and pull tight.

Strip about three centimetres (one inch) of the plastic coating off the free
end. Poke the exposed wire between the coils on the antenna spring base,
REMOVE THE WHIP ANTENNA.

In general the most effective wire is approximately 45 degrees to the ground
and broadside to the base station. When there is no means of hoisting the
wire up, it can be laid out in a straight line on the ground. In this
case propagation occurs with maximum radiation in the direction in which
the free end points.
AnswerID: 48188

Follow Up By: Member -Bob & Lex (Sydney) - Thursday, Feb 26, 2004 at 12:59

Thursday, Feb 26, 2004 at 12:59
What size copper wire? Will household power cable do?Regards Bob
Where to next
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FollowupID: 310088

Follow Up By: Peter - Thursday, Feb 26, 2004 at 16:13

Thursday, Feb 26, 2004 at 16:13
basically any insulated wire will do.
By household power do you mean single core or multi strand flex.

I would use multi strand flex.

Or down to dick smith /jaycar and get a multi strand cable with diameter of 1mm or bigger. It is cheap

What we are talking about is radiating the signal from a wire.

The length is the most important thing so there are no reflection back to transmitter. VSWR is the tecko name.

You can pole the stripped wire into the centre of coax on extension of 910 aerial. Just ensure that it does not touch the body of car radio / anything.

You will then need to set your radio to a manual or whip type aerial for it to function.

I have to do this with my barrett 550
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Reply By: GOB & denny vic member - Thursday, Feb 26, 2004 at 20:17

Thursday, Feb 26, 2004 at 20:17
goodday all
wouldnt it be easier to have a second aerial on the car and carry a multitap aerial in case of breakage or pilfering just unscrew 1 lead and screw in the other

steveimagine a 03 gu 4.2tdin the picture
as i am having trouble sizing the picture
AnswerID: 48254

Follow Up By: Chris (W.A.) - Thursday, Feb 26, 2004 at 22:20

Thursday, Feb 26, 2004 at 22:20
...or just buy a portable fold away HF - there's plenty on the american market plus an epirb!!
Unless you're a radio enthusiast there's no need for big aerials on the front of the vehicle or rear for that matter.One day a week, one weekend a month, six weeks a year.
Chris
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Reply By: Phil G - Thursday, Feb 26, 2004 at 21:24

Thursday, Feb 26, 2004 at 21:24
Thanks a heap to everyone for replying. Yesterday, I knew very little, but having absorbed this info and surfed some of the suggested sites I have a better idea. Those ham guys are crazy - they can invent all sorts of funny aerials.

Interestingly, I had a look at Electric Bug, yesterday at the Wayville show in Adelaide, and they have a telescopic portable HF aerial they call a Super Rod - 9 metres long so its tuned for 8022, but you can hook it up to the autotune for all the other frequencies. They reckon it makes your set perform like a base station. It looks impressive, and is set up in no time. Have to weight up the cost of that ($272) vs about $20 for a home made emergency one.

But I have enough info now, so thanks everyone.

Cheers
Phil
AnswerID: 48266

Reply By: Wayne (NSW) - Thursday, Feb 26, 2004 at 23:04

Thursday, Feb 26, 2004 at 23:04
Maybe I should not have joked about the Sat phone that surrived the rollover becaues it was safely tucked away in its leather pouch in the glove box. All those calculations to run a wire aerial, I hope the batteries in the calculater last.

At the end of the day to each his own.

I will never be convinced a UHF is better than a Sat phone, and you will never be persuaded that a Sat phone will ever replace a UHF.

WayneAlways Out'N About
AnswerID: 48293

Follow Up By: Phil G - Friday, Feb 27, 2004 at 08:06

Friday, Feb 27, 2004 at 08:06
Hi wayne,

We're talking HF here and not UHF - very different.

Looking at the ham websites, it looks to me that lots of these people get more fun out of making an aerial than they do working the radio. Nothing wrong with that. Bit like us having more fun preparing for a trip, than actually doing it :-)))

Sat phone doesn't suit me. Its a fairly lonely device. With the HF, I listen into the skeds and hear whats going on around, and lots of people can listen to me. I get warning of bad weather - one trip we were able to pick the places still accessible and saw the great spots in central Australia when wet.

I make telephone calls from mine, so call my wife/kids every day and have a chat. She didn't mind spending $3,000 for the hardware.

And the best part of HF is that work can't phone me :-))))

Look here too
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FollowupID: 310182

Follow Up By: Wayne (NSW) - Friday, Feb 27, 2004 at 13:12

Friday, Feb 27, 2004 at 13:12
Phil,

Sorry I did mean HF not UHF.

In my line of work the boss has to be able to contact me.

Wayne Always Out'N About
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FollowupID: 310214

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