--- In ham_amplifiers@..., "Peter Voelpel" <df3kv@...>
wrote:
Jim,
Do you think there is any difference in the voltage capacity of
fixed or variable vacuums caps by Jennings specified for the SAME
DC voltage?
73
Peter
### No.
### The point Jennings was making...was IF using a fixed vac cap
as as DC BLOCKING cap.... the vac cap will have HV DC on one side
of it all the time.... and the vac cap will "grow whiskers" on
it's OFC copper plates.... leading to v break down. That's why
Jenning's sez to size the vac cap to a min of 3 x normal no
load plate V.
### Me, I just use normal HEC HT-57's.... and HT-59's. I also
have looked at Draloric's and similar HEC block caps... these
ones look like aprx 2000 pf @ 10 kv, 60 A CCS @ 32 mhz....
and are aprx 3-5" diam.
### Why 11m ops want to use fixed glass/ceramic vac caps for
plate block caps is beyond me. They would handle bags of RF
current though. Probably for big amps. However... 8 x 200 pf HT-
57's will handle 104 A. 4 x 500 pf HT-59's will handle 92 A.
later... Jim VE7RF
________________________________
From: ham_amplifiers@...
[mailto:ham_amplifiers@...]
On Behalf Of pentalab
RICH SEZ... A 15kV - tested Tune-C would do the job - provided
that
the DC blocker cap was ahead of the Tune-C. With a 7000V anode
supply, and a g-g triode, the AC anode potential would be c. +/-
6700V-peak. Since the RF rating of a vacuumis 60% of it's DC
rating, or 9000V in this case, a 15kV cap would do the job. -
note - The "Plywood Box" amplifier used a 15kV tested Tune-C and a
9000V NL anode supply. The Tune C did not arc.
### Rich, when are u gonna read the posts more carefully ???????
We are talking about using a FIXED vac cap.... AS A PLATE
BLOCKER !!!!!!!!!!
