This didn't make it through before, or at least several posts did afterwards
so I stripped it down to try again.
> In a message dated 9/26/2007 8:14:05 P.M. Eastern Daylight Time,
> sub1@rogerhalstead.com writes:
>
> Were it me, I'd start with a search for articles on such conversions.
> They
> may or may not be on the net. I don't recall seeing any in the ham
> magazines, but I wasn't interested in doing a conversion until recently.
> As
> I recall the ARRL Handbook and amplifier books deal with complete builds.
> I
> don't know about QEX.
I wonder about going the 4CX-250 route, or 4-250. Apparently my Eimac hand
book is out in the shop so I can't look up the numbers for the 125, 250 and
400, but I do have a commercial 2-meter amp using a pair of 4-125s and I'd
guess the 4-250s may go that high. the 4-400s? they are as large as a 3-500Z
and maybe a tiny bit taller. If they'd go to 50 MHz (which I think they
will) they might make a whale of a 6-meter amp in an SB 220 case, but as I
recall the 4-400s are a bit more pricy than the 125s and 250s or even the
4CX250s and a *lot* more than 3-500Zs . They'd fit with the possible
exception of the 4-400 and are of a relatively good price. the 4CX 250s were
widely used in VHF amps as well as HF (re the old KWS-1 which I had and the
Collins 6 & 2 transverter) IIRC the 4CX-250s will mount in any position and
should give 600 to 800 out for a pair. Yes they would take a screen supply
but a relatively simple one that should easily fit in the space freed up by
going to the smaller tubes. There'd also be space for a plenum for the tube
sockets and a blower. Of course I remember the old KWS-1 was a great space
heater for my shack in the winter, but a good part of that came from the
75A4 and exciter portion of the KWS-1. . OTOH my old Henry 2K-4 really
throws out a lot of heat. With the 3-500Zs having a typical gain of 10 db I
keep wondering how some are claiming 1500 out with only 75 watts of drive.
It takes me a 100 to get 1200 out and I could use it for a coffee warmer
while doing it. Coffee warmer? I could cook dinner on it.
I realize I've gone from a tank circuit conversion to a major change, but
isn't that what ham radio is all about, or is for at some of us.
73
Roger (K8RI)
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