Hi Al,

OK, thanks for the ideas. My first guess was that i will have
difficulties to find a blower that can give me enough pressure !

I think that there will be less back pressure than blowing all the air
through the socket...

I want to maximize the RF shielding between anode and cathode, by
leaving the smallest space possible in the socket. Doing this, the air
would have some difficulties to travel through... I could also drill
some holes at the other end of the cabinet, but that would reduce the
useful air flow also !

I will have a look on K2RIW's amps. Tnx for the info.

btw, i want to make my amp as small and simple as possible.. I will use
a cathode driven design with G2 grounded and plate resonator made by a
simple 1 turn coil, no line, no PFTE, etc ... (seen on YU1AW's "lazy
builder" page)

My actual concern is to find a simple but stable way to make a 10 pF HV
variable cap. Berylium copper and/or vacuum caps are not common here on
Corsica ! hi hi

73, Patrick. TK5EP.


Alfred Green a écrit :


No, not a stupid idea at all. That's the way I do it on my current
4CX800 2m amp, and I have used that method on several 4cx250 class amps
in previous years. I think its was popularized, if not initiated, by
K2RIW some decades ago in his classic 432 amp.
Three things to watch for:
1) make sure there is a good seal from the outer part of the plate
resonator to the outside world; I use 25mil teflon sheet as a chimney
with clamps made from brass strip.
2) ensure there is an exit in the grid compartment so that the air can
flow through adequately.
3) put some mesh on the blower inlet to the plate cavity, otherwise the
resonance will be affected by the fan rotation. Gives a subtle, but
noticeable AM buzz.

Good luck with the project.

73 Alf NU8I (aka G4ABB,ON8KL,VK6GA,PZ5AG, etc)
Scottsdale AZ DM43an