[Amps] Fan Noise in GS-35B Amplifiers.

[Robert Briggs]

Hi all, I have been constructing VHF amplifiers 6 and 2 meters for VK 
hams for a few years now..I developed my own cabinet construction 
technique and I incorporate a Papst 6424 HR 12-28 volt fan to pressurise 
and cool the Anode compartment...The air runs up through the tube cooler 
and exits through a Teflon chimney on the top cover..It is easy to 
incorporate a duel voltage switched DC power supply controlled with a 
relay on the PTT line to vary the fan voltage and speed on TX/RX..

I use another small muffin fan on the cathode compartment to cool the 
cathode and exhaust the air through the side of the amplifier..

With the big Papst fan located within the amplifier case the noise is 
well muffled, still, one cannot have good air flow without some noise..

Talking about water cooled GS-35B tubes...I constructed my own water 
jacket for a GS-35B tube in a single band 160 meter amplifier..I have 
run this amplifier trouble free for years..I use a 12 volt powered pond 
pump to circulate the water..

73..Bob..VK3ZL..