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From: liz@poppyrecords.invalid.invalid (Liz Tuddenham)
Newsgroups: sci.electronics.design
Subject: Re: Valve frequency multipliers (followup)
Date: Sun, 6 Apr 2025 20:56:43 +0100
Organization: Poppy Records
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john larkin <jlArbor.com> wrote:

> On Sun, 6 Apr 2025 19:12:08 +0100, liz@poppyrecords.invalid.invalid
> (Liz Tuddenham) wrote:
[...]
> >The formers were some NOS ones that had about 40 turns of wire on them,
> >bfeore I stripped them and wound on 7 turns for 50 Mc/s.  That looks as
> >though they were originally intended to work somewhere around 1 Mc/s and
> >presumably the ferrite core would have been optimised for that frequemcy
> >range. 
> 
> 
> 455 KHz IF maybe?

Probably not: the wire was layered, whereas all the 455 Kc/s I.F.
transformers I have seen were wave wound with Litz wire to give the
highest possible 'Q'. - and they had a lot more than 40 turns.
> 
> >
> > I am now beginning to wonder about the other inductors in the crystal
> >'pulling' circuits, which are running at about 15 Mc/s and come from the
> >same batch.  The behaviour of the oscillator had been somewhat strange
> >at times, so the cores could be causing trouble there too.
> 
> I've wound high-Q inductors on a Sharpie.
> 
> https://www.highlandtechnology.com/Product/T850
> 
> All the commercial inductors that I tried (pcb revs A and B) fried.

I'm not after a particularly high 'Q', but if the coils are stupidly
'flat', that might explain why I had such difficulty getting a good
signal out of the oscillator.  I'm in unknown territory with this
circuit, as the crystal frequency has to be modulated on transmit and
pulled on receive.  The partially-complete circuit of the Xtal
oscillator and multiplier chain is at:
http://www.poppyrecords.co.uk/other/Transceiver/XtalOsc5a.gif

The block diagram explains the reason for needing these
particularfrequencies:
http://www.poppyrecords.co.uk/other/Transceiver/Blockdiag6d.gif

I wind my air-cored coils on the shanks of drill bits or on the barrels
of nut-drivers to give a known repeatable diameter.  The wire is some
fairly hefty stuff with insulating varnish which has to be filed off
before soldering (if doesn't self-flux like many modern winding wires).


-- 
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk