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Sets, Parts and Service Information Offered (private sellers only, exact price required, no swaps) You may announce components or sets for sale or offered free here. Private collectors only - no traders. You must include an exact price. No swaps.

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Old 24th Aug 2019, 8:46 pm   #1
Bryan M
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Default Minisynth VFO

PCB for this Cirkit kit of the 80s for (as I remember) a 5-6MHz synthesized VFO. It measures 5.5 by 9.5 cm and is quite densely packed (but no SM).

No other information apart from the circuit diagram here:

https://www.qsl.net/va3iul/Homebrew_..._VFO_G4JST.gif

FOC for anyone who remembers it or wants to play.

Bryan
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Old 24th Aug 2019, 9:30 pm   #2
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Default Re: Minisynth VFO

It's a free-running VCO and a crystal oscillator driving a summing-loop PLL.

David
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Old 25th Aug 2019, 8:07 am   #3
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Default Re: Minisynth VFO

Have you got the table's Bryan? Is this from Elektor or ETI?

Andy.
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Old 25th Aug 2019, 9:14 am   #4
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Default Re: Minisynth VFO

I knocked up something like that in the dead bug style. It made me a tunable LO
for covering 10m on a multimode CB. Pity that some unobtainium IC died in the AF PA / AM Mod section and afterwards the thing was unusable.
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Old 25th Aug 2019, 9:55 am   #5
Bryan M
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Default Re: Minisynth VFO

No, Andy, no more info. The board was bequeathed to me some years ago and it's just surfaced. I have a page from a Cirkit catalogue somewhere but it says little more than what David above says. The link I provided was all I could find.
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Old 25th Aug 2019, 10:18 am   #6
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Default Re: Minisynth VFO

In the early days, some stuff marketed by Cirkit appeared as construction articles in Ham Radio Today.

As for how that system works, G3ROO published a multiband version of one we'd designed in Radcom in the early 90's (It got Ian the Talbot-Wortley trophy!) I reprinted it in the ARRL handbook (1995 on)

The Cirkit schematic tells you all you need to know except coil recipes. Parallel mode crystals aren't all that common these days

David
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Old 25th Aug 2019, 1:05 pm   #7
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Default Re: Minisynth VFO

I think I may have that HRT article in one of my files somewhere, I'll take a look.
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Old 25th Aug 2019, 1:41 pm   #8
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Default Re: Minisynth VFO

Ah, after several plunges into the dreaded 'big yellow file', I have found it. It's the VHF Minisynth with the switchable xtals, but it uses the same idea - any good?
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Old 25th Aug 2019, 9:54 pm   #9
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Default Re: Minisynth VFO

The G4JST & G3WPO minisynth article starts on page 38 of the April 1984 edition of Ham Radio Today which is available on the American Radio History website.
https://americanradiohistory.com/Arc...RT-1984-04.pdf
The PDF is not the greates quality but table listing the Toko coil & capacitor combinations for different bands and IF's is just about readable.

The VHF Minisynth is featured in the October 1984 issue but is a rather different beast so a different PCB is needed.

Mike
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Old 26th Aug 2019, 9:21 am   #10
Bryan M
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Default Re: Minisynth VFO

Thanks for the replies, particularly Mike for the HRT link. It's designed for a much greater range of frequencies than the limited range I suggested.. The board pictured in that link is the one I'm offering. The Toko coils may be a challenge.

So, still on offer, or do I put it aside again for a rainy day?

Bryan
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