On Friday 10 September 2004 08:36, Steve Thompson wrote:
> On Thursday 09 September 2004 21:34, Steve Katz wrote:
> > > Has anybody got experience of the Amp listed in the Tech web pages of
> > > 6m.com? It was for 2m using 2-4cx250b (shown as Horizons 12-62) zip
> > > file c5
> > > It looks easy to build, and has a PI output network.
> > >
> > > //The 6mt.com website is so painfully slow to load I don't have the
> > > time to look for this; however a pi-network for high power on two
> > > meters seems like folly. Every dual 4CX250 amp I've ever built for 2m
> > > (several of them) always used the tubes in push-pull with tuned plate
> > > lines, tuned by a tiny bit of variable C between the tubes, and link
> > > coupling.
> Search around for the W2GN design using a pair in parallel, it works a
> treat. I modified the grid circuit to have separate bias control, so it
> will work with unmatched tubes. Personally, I don't like link coupling -
> it's possible to get false indications of optimum loading.
Ooops - what I meant was - tuned link coupling. A variable untuned link should
give you monotonic loading adjustment, the same as a variable series
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