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
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|