Topband: Russian Vacuum Variables on EBAY

Charles Moizeau w2sh at
Tue Jan 11 10:30:13 PST 2011

> Date: Mon, 10 Jan 2011 14:25:26 -0500
> From: olinger at
> To: k6uj at
> CC: topband at
> Subject: Re: Topband: Russian Vacuum Variables on EBAY
> Bought two 1200 pf 4 kV for use on big 160 antennas out at N4AF, from
> QRO-stuff.  No problems and have done the job out in remote box for
> seven or eight years now. Very stable.  Quite large, drive shaft is
> NOT 1/4, 12mm or almost 1/2. Most likely have to fabricate a knob or
> reducer.
> Those big things are the final answer, absent direct lightning
> strikes, for going the distance QRO.  Prices for Jennings brand new
> retail are simply awful new, but on eBay the Russian listings are
> affordable.  This is most like what we bought:
> 73, Guy.
> ************************************************************
> On Sun, Jan 9, 2011 at 9:00 PM, Robert Harmon <k6uj at> wrote:
> >
> > I see some good prices on new Russian vacuum variables on EBAY.  Thinking about getting several
> > for a vertical tuning unit I am planning.  Anyone bought vac vars from the Russian EBAY vendors,
> > good results ?
> >
> > tnx es 73,
> > Bob
> > K6UJ

I've just looked at this auction listing, as well as visiting:

which is now closed.  

The prices shown, plus shipping, are just a bit north and south of $200 for these glass-encased capacitors.

On my desk is a Jennings CMV1-650-0005 that I cannot distinguish from new, and it arrived here last week for $195, plus a nominal amount for shipping from Marietta, GA, USA. Transit time via FedEx was 48 hours.   It is ceramic, less fragile than glass, offering 8-650 pF @ 5kV. and with 10 turns' rotation required for its min.-to-max. capacitance variation.  The 0.5-inch diameter shaft came with a reducer to 0.25-inch diameter, mounted by the seller.  Fitting a 10-turn dial will be easy.  

This gem will be set to about 255pF and then installed at the base of my 0.37 wavelength (85'up + 85' out) inverted L antenna where, aided by 44 in-ground radials with an aggregate length of just under a mile, it will replace a large "bread-slicer" capacitor and restore my 1.1:1 SWR reading.  I feel quite safe that with such a generous breakdown voltage rating I shall have no problems with my almost-always output power of five Watts, but I must give a bit of thought to better protection from lightning damage.

This capacitor's seller is the well-known and long-established, MaxGain Systems, whose principal I deem to be a worthy and reputable individual.  He knows much more about vacuum variable capacitors than I can ever hope to learn, and, in my estimation, he has the integrity to willingly settle fairly any problem that might arise from a business dealing with his company.

Over the Christmas holiday I  read the The Economist of 11 December 2010, pages 29-32, "Briefing: The State of Russia", which I highly recommend, and from which I now believe a likely consequence of my recent purchase to be my not having dealt in stolen goods; nor did I worsen the US' balance of payments deficit by adding to this country's substantial trade imbalance.

73 (or perhaps QRP-speak 72),

Charles, W2SH       



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