Chris, my 3C90 transformer has about 16 turns on each winding. (I say
approximately as I need to adjust by a turn or two between summer and
winter due to absorption/detuning by trees. I would suggest using the
thickest wire you have in case you want to run higher power in the
furture.

As for the variometer, mine covers about 200-500mH and this will tune
about twice the width of the 136kHz band (in conjunction with my big
coil). Coincidentally it also tunes the 472kHz band when the big coil
is removed.

Mike, G3XDV
==========

> yes, I still have trouble with the workshop alarm going off when I TX,
> but seemingly only at night, for whatever reason! Isolation is
> something I need to add. I have a 3C90 core spare and will wind a 1 :
> 1 transformer for now, just for isolation. How many turns should I use
> for best efficiency? I will probably use either 1.5 mm enamelled wire,
> or maybe some Teflon covered stuff.
>
> I also need to tame the variometer, it's obviously got far too many
> turns on it as just a couple of degrees moves resonance a long way. I
> picked up a 2 axis variometer, possibly a goniometer, that I may ise,
> with a motor drive. Photos at http://www.chriswilson.tv/goniometer.zip
>
> I only gave a fiver for it, so no big deal if it doesn't work out, but
> I am about to check what inductances it covers. I think it should
> withstand the voltages OK. What do you reckon? It would be easier to
> motor drive then the variometer in my loading coil.
>
> Thanks for the kind words about my progress. Most thanks should go to
> G3YXM for helping me get my amp done and reliable, he's been a
> Godsend, as have you gentlemen on here.
>
>
> > I agree with Stefan. A transformer (using a suitable core material
> > such as 3C90) gives you more flexibility in the future It also
> > provides the opportunity to isolate the RF ground from the mains
> > supply ground which can improve EMC both on transmit and receive.
>
> > Well done so far. Your signal is very impressive with such low RF
> > power.
>
> > Mike, G3XDV
> > ==========
>
>
>
>
>
>
>
> --
> Best regards,
>  Chris                            mailto:[email protected]
>
>
>
>
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