I would have to disagree with the 2500V in the case of the GS35
specifically.? To get 1.5KW out, I think the Ig will be too high
at that low of a voltage.??
I ran 4300V on mine and that was very nice from a minimal Ig
standpoint although I think 3500V may be the sweet spot
compromise.? The tube spec is 3KV CCS and 6KV pulse.? Of course
with any proposed tube you want to use, getting a check with a
suitable BDV tester is going to be step one.??
An additional benefit of the higher HV::? The Soviet tubes in
general tend to be a bit less gain than the Eimac and the higher
voltage will help with the gain as well.
73/jeff/ac0c
alpha-charlie-zero-charlie
On 12/26/2023 2:15 PM, Steve wrote:
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First thing I'd do is copy the spreadsheet and revise the
dropped Ep to no more than 2500V, perhaps 2550 at most, then
design for that reduced value. Unless you're in a commercial
establishment, with commercial-quality mains and components, Ep
always seems to drop below our best hopes? 8-/
Steve, K0XP
On 12/26/2023 8:05 AM, desmond auld
wrote:
Hal,
Yes, one of concerns is "committing" to a tube that dries up by
way of availability.? That's why the GS35 and Gu43b are on my
radar,as they seem so plentiful.? If i do get an amplifier up
and running of my own creation i will invest in many spares to
keep on the shelf and circulate every year to keep fresh ish.?
The old 811's in my existing amp has are now getting relatively
expensive for a 65w dissipation tube,and the 572B's are out of
hand cost wise considering they are all now Chinese of
poor/average quality, so i understand the concern of going down
a dead end.??
I have spent some time today reading, and plugging in numbers
into the wonderful G3SEK spreadsheet to calculate the values of
C1, C2 and L1 in the tank circuit of an imaginary amplifier
based around two GU43b's in parallel. I have assumed some
things, obviously, like the HV will drop under load to 2700vdc
from circa 2900vdc.? I have modified the spreadsheet to have a
tab for each band, 10-80m, that i'm interested in, and also a
summary sheet with what a beginner such as myself thinks is
important.? i would be VERY grateful if those that know what
they are doing could critique my assumptions and the outputs.?
Spreadsheet attached , with summary copied in below.
Does anything look way out of wack in my assumptions, or not
practically possible in my outputs?
I went looking in my "capacitors for the big amplifier" box and
have a good section of high voltage door knobs, and two
beautiful vacuum variables, that i could use.? One is very
large, 25KV rated 15-350pf, and another is smaller 15-90 pf 40Kv
rated.? I had almost forgot i had these things!? I'm getting
quite excited. :)?
Has anyone any good links for winding tank coils with
calculations etc??
Alex from UR4LL has the GU43b tubes in stock and i am talking to
him at the moment about purchasing some along with some other
parts i may need.? He has a beautiful EImac 4cx 10,000 for sale
if anyone is interested.? I'm not man enough :)
Thanks guys
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