[Amps] Question about GS-35b efficiency

[Ryan Foster]

Thanks, and it does help.  I haven't built the power supplies at all yet, so
it isn't to late to turn back at all, but I probably won't.  The whole topic
though really just made me wonder if there are similar (or one that is
double since the idea for one was a two tube) surplus tubes that I could buy
that might be more efficient.  I bought these really because I saw the specs
and at a hundred each couldn't pass them up.  I don't really know many of
the surplus Russian tubes to know if there is anything better for me to
buy.  It also makes me wonder about the efficiency of the gi7b's in service
since I have never checked, but I do remember thinking they were a bit shy
of what I expected output-wise.

If my next best option was the 8877 though, that is a whole lot of
kilowatts...

--Ryan, w8cya

On Fri, Dec 18, 2009 at 2:57 PM, Bill, W6WRT <dezrat1242 at yahoo.com> wrote:

>
> REPLY:
>
> By now I have had several emails on and off the reflector which pretty much
> validate my own experience with the GS-35b, and none that contradict it. My
> conclusion is that while the GS-35b will indeed produce 1500 watts output
> with
> about 85 watts drive and is a reliable tube, the efficiency is less than
> other
> tubes such as the 8877.
>
> This is not necessarily a show stopper - a loss of a few hundred watts of
> DC
> power may be a satisfactory trade off for the very low cost of the tube.
> All
> designs have trade offs of one kind or another. It's just a choice the
> designer
> and builder have to make. Since you already have them in hand, and if your
> power
> supply can handle it, I'd say go ahead and build it. It should work ok and
> last
> a long time.
>
> My guess - purely a guess - is that since the GS-35b was originally
> designed for
> pulse radar service, it was optimized for that and not for linear amplifier
> service. There is probably some difference in the internal geometry, most
> likely
> the grid structure. This is most likely the root cause of the efficiency
> question.
>
> Hope this helps.
>
> 73, Bill W6WRT
>