[Amps] Drake L4B to 6 Meters Help

[Alek Petkovic]

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.

-- 
 From sunny Binningup
Our new house.
https://17coronation.wordpress.com


Family Businesses:
SP Electrical. www.spelectrical.net.au
The Velvet Fox. www.facebook.com/TheVelvetFox
Smart Design Electrical. 0417 602 032
Perth Interiors. https://www.instagram.com/perthinteriors/


---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus