It could be something to do with your tuning procedure.
On 6m with a SB-220 for example, the tuning procedure is a many step
process of starting with the load cap, then tune cap, then load, then
tune, ad infinitum. Each time, you get a little higher and then a little
higher and so on, until you hit that sweet spot.
Email Lou, W1QJ, in private. He is the guru for the 220. The same
methods may work for the L4. For a few cases of beer, he may be able to
expand, correct or refine on the above process.
Good luck,
Alek. VK6APK
On 12/12/2016 11:13 PM, Ron Youvan wrote:
On 12/12/2016 10:01 AM, Michelle wrote:
I have converted a Drake L4B to 6 meters and I seem to be stuck at
750 watts output, I have tried a PI input (no change) , different tank
coils
(less output), The current setup listed below I have checked both
input and
output with a antenna analyzer at 50.125 and they both seem to be
right on
spec. Thanks in advance for your comments.
Plate volt 2300 under load
plate current .650
Grid 220
Drive 100 watts
Output 750 watts
Input circuit T match (works as it should, flat match)
Plate cap 3-30 pf vacuum variable
Load cap 25-350 pf (original Drake plate cap) 1/3 meshed at max output.
Tank circuit PI-L, L1 3 1/2 turns 1/4" copper tubing 1 1/2" id, L2 4
turns
16 ga 1" id.
RF choke 42 turns of 22 ga on 1" porcelain form
Bifilar choke Stock Drake 20 turns each leg of 10 ga on 5/8 ferrite rod
All grid pins directly grounded to chassis
Parasitic suppressors are 47 ohm 2 watt with 1 turn 16 ga
T/R relay changed to vacuum relays
What am I missing here? Has to be something really simple I'm
overlooking,
Thanks again for your comments,
You don't say your modulation mode. (CW - FM or SSB whatever that is)
I'm no expert, but you are achieving 50% efficiency, that doesn't
sound bad to me for 6 meters, to get more power out you need more
power in.
I would double the plate Voltage. That increases efficiency.
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