--- In ham_amplifiers@..., "Peter Voelpel" <df3kv@...>
wrote:
Jim,
Grid dissipation is measured by ohms law, grid voltage by grid
current.
Since the grid is at ground, you just measure the cathode voltage
with
a scope.
### whoa. Are you saying RF cathode V x DC grid current
= grid diss ????
### That equates to way below 200 w of grid diss.... based
on 45 ohm input Z... and 800w of drive . I can see we
are well within the grid diss ratings.
For calculation of efficiency you have to deduct the drive power
first
in GG, about 70% of the drive power is seen as output power.
Drive power is not lost totally as with GK.
### I never deduct the drive power... since it really enhances
the eff in the end anyway... another benefit of GG. Bottom line
is... "apparent eff" goes up... anode diss goes down a bit.
If both capacitors of your input network are the same value you
have
no transformation, you will have 50 ohm input from the transceiver
and 50 ohm output to the cathode side.
### yes... u can see that effect on GM3SEK's excellent pi/ pi-l
spreadsheets. Funny how every arrl handbook/qst article
using fixed silver mica's always used same values for C1 +
C2.... which never worked.
I would expect the cathode impedance smaller at that power,
probably
30-40 Ohms.
#### it's about 40-45 ohms. The gain is about 11.54 db at
11.5 kw out.
### Funny thing is... with just 100w of drive... power out is 3
kw [ 3CX-6000A7] It appears on all these big tubes... that
gain is higher with low drive levels... then decreases... with
increasing drive levels.
### The 3000A7 is abt 1500w out with just 50 w of drive.
### Tubes like the higher gain YC-156 have aprx 25 ohm input Z.
Gain is almost quasi proportional between plate load Z and input
Z.
I use that tunable pi-network on my 3CX3K amp, but used a smaller
capacitor on the ouput then on the input. My coil is switched as
well.
I would like to use ganged capacitors there and ganged with a
roller
at the same time, should work with that low circuit Q.
### Henry tried that in the 4 K ultra. Trying to get it to
track was [still is] a real bitch. I wouldn't do it. For
160-10m... u need 4000 pf caps. If u pad smaller 2100 pf caps
like I did for 160m... ur tracking will be out to lunch. You
also seem to get anomoly's from one band to the next.
Any idea of the price of the 4?H roller by multronics?
### No clue It appears identical to their 28 uh unit that
was featured in many qst/ handbook articles over the years...
excpet the little 4.4 uh unit is shorter... and uses 8 ga wire
[.128" solid tinned alloy wire]. I believe the 4.4 uh unit also
has the same tapered pitch at the high freq end.
### Multronics is now a division of Cardwell condenser corp.... I
think it's just cardwell condensercorp.com
Later... Jim VE7RF
73
Peter
