Emergency aerial for Barrett 950 HF radio

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

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

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!

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

.

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

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.

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.

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

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

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