Thread: Autotune Antenna question

The autotune is an ATU.

If you have a combined length of the whip and long wire that are close to a factor of the full wave the ATU should be able to tune.

Remember that a modern HF autotune from Codan or Barrett is capable of tuning antenna length between 40 metres and 2.5 metres.

A 1/4 wave antenna length for VKS737 channel:

1. 5455KHz = 13.75M
2. 8022KHz = 9.35M
3. 11612KHz = 6.46M
4. 14977KHz = 5.01M
5. 3995KHz = 18.77M
6. 6796KHz = 11.04M
7. 10180KHz = 7.37M

Nothing should prevent you making up a long wire of the correct length for each channel with a fitting that connects directly to the top of the ATU itself.

One of my mil HF radios comes with a long wire antenna that has plug and socket connections that allow you to select the correct length for the desired frequencies.

Thanks for that Diana.
I was pretty sure it would but thought I would get confirmation.

Didiman

As Di says these are Antenna Tuning Units (ATUs).

Both the Codan 9350 and the Barrett 910 tune the antenna to close to the 1/4 wavelength for the relevant frequency. They do this via slightly different methods but basically try to match the electrical length internally with the addition of the whip to this specific length.

My thoughts are that attaching a long wire would not be good for the ATU as they are specifically setup to work out a tuned length with the whip attached NOT a long wire. It may work but then again it may not and that could prove expensive.

Why add another long wire to replace the whip when it would be much simpler to just carry a dipole antenna and swap the RF connector out from the ATU and attach the dipole.

This is what I used to do with my Barrett when traveling about in the wilds. It served as an excellent substitute for the ATU when appropriate things, like trees, were about. It also served as a backup should the unforeseen occur and the ATU unit became a NFU.

The dipole kit takes up much less room than a wire tuned whip as a backup.

Just my 5c worth.

Cheers,
Iain

Hi Iain

You are of course correct about the design factors, but given the electrical length at both ends of the frequency bands the autotune is capable, it "should" be able to accomodate the lower frequencies in the 150 metre down to the 30 metre bands where VKS737 operate but you may find the ATU is unable to accomodate frequencies in the 9 or 10 metre bands (9 metre band = 27MHz). Again you are more likely to be able to tune if the wire length is at or approaching 1/8 or 1/4 or 1/2 of the desired wave length.

Remember the NVIS kit supplied by Codan contains an antenna element more than twice as long as the standard whips supplied with the 9350.

Diana

I did think it might tune a random long wire but thats OK. I used to carry 1/2 wave dipoles for 10, 15, and 20 metres when on the yacht but I did not have a tuner for the TS 520.
My old Tracker Lynx with tapped whip has given up the ghost and not worth repairing so I am getting more up to date with a Barrett 550 and Autotune.
So I will make some dipoles and see if I can extend the range.

Didiman