Portable HF Radio

The people at Barrett are very helpful - sure that would be happy to offer an opinion. No point in conjecture, when you can get the good oil. Give em a call - there's a link at the vks737.on.net site. Get me outa these suburbs !

G'day Mike,

I checked out the Barrett website, and had a good read up on the 940. It is a very impressive little unit.

I don't think there should be many problems with it, in the right hands it could be used to communicate over a fair distance quite efficiently.

However, as with all portable stuff there could be issues with power supply - especially if your transmit/receive ratio is high.

Consider back up batteries, or better still, some form of portable vehicle power setup. Consider also the antenna tuning unit.

disregarding atmospheric conditions and other types of interference, the effective range of HF transceivers quite often comes back to two very basic things. The efficiency of the antenna being used. and the expertise of the person operating the set.

In the wrong hands the most powerful transmitter in the world is useless. In the right hands, and with some serious thought on the choice of antenna, some of the smallest output HF sets have achieved unbelievable distances.

I have personal experience [was on the team] of a world record back in 1963. Melbourne to Perth using CW [Morse Code] on a radio with a power output of 200milliwatts, and thats bloody tiny.

Took us 3 nights to achieve it, but we did it in the end with some very judicious antenna adjustments.

Get good at working your gear.

BTW, what do they cost? I am more than a little bit interested.

enjoy the bush

DennisN

What about a cheaper version an older codan and long wire Aerial,
Then for local comms between the men a couple of uhf hand helds.

Have a look here this type of thing may be of help .
Search arround for some other sets.

http://www.desertaccess.com.au/html/for_sale.html

Also weight and size wise try

http://www.qmac.com/Portable.htm
http://www.qmac.com/Minipack.htm

Also see for portable aerials
http://www.bushcomm.com.au/plw.htm

To work out long wire aerial lengths

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.

HF is a pain. Go for UHF--no fuss with aerials and you will have enough range for your purpose.