From: patriot121@msn.com
To: mausoptik@btinternet.com
Subject: RE: [Amps] Question about GS-35b efficiency
Date: Fri, 18 Dec 2009 17:49:33 -0800
Speaking of GS-35b efficiency, What is the efficiency of a pair of 3-500z's??
Say in a HL-2K
Mike
KC7NOA
>
> if you can get hold of VK3ZL I know he's recently built a GS35 amp and did a
> very professional job of it, so he'll no doubt have some answers
>
> cheers
>
> Dave G0OIL
>
> --- On Fri, 18/12/09, Jim Barber <audioguy@charter.net> wrote:
>
> From: Jim Barber <audioguy@charter.net>
> Subject: Re: [Amps] Question about GS-35b efficiency
> To:
> Cc: "Amps reflector" <amps@contesting.com>
> Date: Friday, 18 December, 2009, 6:45
>
> And I'd like to hear more about expectations of what a single GS-35B
> will do under in-spec operating conditions. Bill's numbers are in-spec
> at the edge of the published limits. My question has to do with how many
> hours can expect to get out of one run at those limits. I've heard 500
> hours - not enough!
>
> The reason I ask is because I'm considering retiring/selling off my
> PA77's and spare 8877's due to age and high eventual replacement costs.
> The problem is - what to replace them with? 3-500's are the current
> price/performance kings and I already own a 3KA, but what new or newer
> 3-500 amp performs in the same league as the PA77 or the 3KA? Then
> there's always the new solid-state stuff... The ALS1300 looks very
> tempting at the street price, but I wouldn't exactly put it in the same
> overall manufacturing quality category as the others mentioned here.
>
> I may have just convinced myself that there's no "best" answer. I
> suppose to summarize I'm getting a bit nervous about long-term cost and
> availability of ceramic Eimacs, as well as *any* continued availability
> of Russian surplus tubes. Perhaps an 'elite class' solid-state amp will
> appear somewhere on the market?
>
> Solid-state... Admittedly 'biased' gut reaction: Blech! Oh wait... Maybe
> they're actually biasing those things these days. ;-)
>
> 73,
> Jim, N7CXI
>
>
> Bill, W6WRT wrote:
> > I have a question about the plate efficiency of a GS-35b amplifier.
> >
> > I have built two of them for 160-10 meters, and while they worked ok, the
> > efficiency was not as good as I expected. In both cases I ran them at 3
> > kVDC and
> > in order to get a full 1500 watts out, had to drive them to 1000 mA plate
> > current. That equates to about 50% efficiency, which seemed a bit low.
> >
> > In both cases, I removed the GS-35b and replaced it with an 8877. With no
> > other
> > changes except bias diode and heater transformer, I was able to get 1500
> > watts
> > out with only 830 mA plate current, an efficiency of 60%. I swapped two
> > different GS-35b's with the same result. Both were brand new tubes. Results
> > were
> > essentially the same on all bands, with a slight drop off on 15 and 10
> > meters
> > with all three tubes.
> >
> > With all of the different tubes, I set the bias for a ZSAC of about 200 mA.
> >
> > I have spoken to two European hams and one US ham and they have reported
> > similar
> > results.I wonder if the GS-35b might achieve higher efficiency at higher
> > plate
> > voltages?
> >
> > I would appreciate hearing from anyone who has made similar measurements.
> >
> > 73, Bill W6WRT
> > _______________________________________________
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> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
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