Re: LF: LF coil tuning

[Andy Talbot <andy.g4jnt@gmail.com>]

The Toko range of coils come with the option of an aluminium tuning slug which amounts to much the same thing.   It is often preferable to ferrite, being more stable with temperature and less prone to breaking when used with the wrong tuning tool.   It typically gives a 20% range from 0.8 - 1.0 of the original L

 

I  used it as a quick way of adjusting the tank on the latest class E Tx without removing turns, but found adjustment wasn't critical and could all be done by varying the caps.    L could be shifted around 10% just placing a shorted turn .around one end of the tank - it didn't get warm or give any detectable additional loss.

 

I've also tried using a Cu tuning plate on an adjustable L in a HI-Q antenna matching in the past, using a screw to alter the distance from plate to the end of the coil.  It  somehow 'felt wrong' or unethical,  even though it worked well enough.

 

Well worth a try anyway

 

Andy

www.g4jnt.com

 

 

On 29 January 2011 23:10, Peter Dodd <g3ldo@o2.co.uk> wrote:

The traditional method of tuning an LF loading coil is to use a variometer.

I have been investigating methods of tuning coils for mobile use and one method that appeared briefly  in one of the ARRL Handbooks of the 50s was the shorted turn method of tuning.

I tried a home made coil of 136uH on a 5cm diameter former and using a shorted turn of 2mm insulated wire and obtained a tuning range of 32uH. (136 - 102uH).

Has anyone out there tried this?

Regards

Peter G3LDO