--- In ham_amplifiers@..., R L Measures <r@...> wrote:
On Sep 23, 2006, at 1:35 AM, pentalab wrote:
### These 1500-2000w amps just bore me to tears. IMO...
it's just as easy to build a big one as a small one.
Lifting an 85lb transformer is not easy for this old fart.
##### Use a cum-a-long hooked to a basement beam... or one of
those small devices used to lift small engines. Me... after
tearing the crate apart.... I slid the 253 lb Dahl straight
across from the pallet it came on, to the new RE-enforced
cabinet. I re-enforced it with a sheet of 1/4" aluminium on
top... and unistrut below...used 4.25" dolley wheels.
### Rich.... get some help....from ur helper babe... or ask Riley
H to give u a hand, the next time he stops by... for tea.
.
... since you will never read any... "how to
build a 5-15 kw linear" in any ARRL hand book / QST article.
The laugher is that W1AW had an Alpha 2, 8877 amplifier until the
ARRL sold it to because it had a habit of zapping 8877s. The
purchaser of the amplifier, QST Editor Mark Wilson, installed a
low VHF-Q parasitic suppressors and apparently put the amplifier
to good use.
### Kilobuck 8877's are about the least cost effective.. throw
away tube one can buy these days. You can buy a 3CX-3000A7 brand
new... with a 3 yr - 12,000 warranty for a paltry $50.00
more... and have it rebuilt over and over and over. Instant on
too... and does an easy 5300 watts out... with 200 w of
drive.... or for you legal limit types.... 50 w of drive will
produce 1500 w out.
### Ted Henry agreed with me... said the 8877 for HF... was a
dumb way to go...... unless available as MRI pulls.. or u got
deep pockets. Can you imagine spending 2 grand to re-tube a
2 x 8877 Alpha 77-SX ???
### Alpha's newest amp is gonna use a single 8877... no vac tune
cap... and no pin diodes ! They just don't ..'get it'
### You can buy 2 x brand new YC-243's for a tiny bit more..
[socketless version of a 6000A7 GG triode] For $2200.00 you
can get a brand new Svetlana 3CX-10K
### All as it amounts to is ... either using bigger
components.... or doing stuff like paralleling 8 x 200pf @
15 kv HEC ceramic doorknobs to make a plate block cap assy.
With one or two thousand ohms of of RL, 1600pF is not necessary
for the DC blocker cap at MF/HF.
### I have heard everything from way more [9000 pf] to
slightly less. I can't find any two engineering books that are
evenly remotely close.
### I figured for 1.8 mhz... 1600pf would do the trick. For the
high bands, the caps current rating goes way up.... thank god...
cuz the current through those caps on the high bands is just
bizzare.
#### How much do you think is needed... for say a 1500 ohm
RL @ 1.8 mhz ????
Later...... Jim VE7RF
...
cheers, Jim
R L MEASURES, AG6K. 805-386-3734
r@...
