--- In ham_amplifiers@..., R L Measures <r@...> wrote:
On Sep 25, 2006, at 4:30 PM, pentalab wrote:
--- In ham_amplifiers@..., R L Measures <r@...>
wrote:
### when guys tell me 1/2" tubing tank coils run so
bloody
hot on 10m, they require 100-200 cfm....
Rich- Water-cooled Cu tubing tank coils and water-cooled vacuum
capacitors are common in larger commercial amplifiers.
### Jenning's only list's one water cooled cap...1000A !
Rich Sez... Jim -- A 1000A rating is barely enough for a tank Q of
15 and a tube such as the 8973. (18v, 650A filament)
#### Nobody in their right mind [except Tom Rauch] is ever gonna
run a loaded tank Q of 15 ! Using the 'new' formulae for
calculating tank Q [entire network Q]..... use a Q of 8-10 ...
and circulating currents through the caps/coils/bandswitch
contacts, etc... are minimized. With lower plate load Z's...
like 1000-1500 ohms...... 2-3-4th harmonic suppression on a PI
is improved.... compared to much higher plate load Z's. Mono
band yagi's, etc.... are going to look like a sky high Z on
their 2nd harmonic anyway.
## For broadcast stuff..... they parallel vac caps together...
standard procedure. They will typ parallel one or more
variable caps ... with one one or more fixed ceramic vac caps....
via enonourmous wide buss bar to minimize stray L... and to
handle the RF. Paralleling stuff for more current has to be done
right..... to evenly distribute the current.
Later... Jim VE7RF
cheers
R L MEASURES, AG6K. 805-386-3734
r@...
