[Amps] 76ca

[Han Higasa]

Hi Wayne san and all in this thread

Thanks for six meter QSOs on 2008 season.
Its a time for maintenance.

I think a basic function of plate suppressor is to 
provide low impedance at fundamental frequency 
(50 MHz) and high impedance at higher frequency
for an adequate Q-dump of tank circuit.

1. The R in a suppressor should sustain an energy 
  rising across suppressor coil by fundamental 
  frequency. If an inductance of the suppressor coil
  is too much, R with higher wattage should be used.

2. The inductance of the coil should be larger for
  the tubes with higher plate lead inductance such as
  3-500Z or 4-400As, while relatively low-L should
  be used for low lead inductance tubes such as 
  800A7, 1200A7/Z7, 8877 or 3000A7 etc.

I think the original suppressor had more inductance
than required at 50 MHz, and the R did not sustain 
the power generated by a RF current of fundamental
frequency.

In this case you should replace suppressors suitable
for VHF use. I recommend a straight copper strip with 
8 or 10 mm width in parallel with 2x100 ohm 2W or
3W resistors. I mean resistors with  "[" style copper 
strip - it is no need to wind it around resistors. 

For a plate choke for six meter amp I am using RFCs 
with 40 turns of 1.2-mm dia former wire close wound 
on 1/2 inch Teflon rod. But if no barn or smoke observed
on original RFC it must be OK for six meter use. 

I hope to hear you again with strong signals on next season.

73 de Han JE1BMJ