[snip]
Seems to be alot of hams going to the GU84B tubes for their Big
amps over the 8877 or even the old 4-1000.
[snip]
I agree. Here's the breakdown:
The 8877 tube is hellishly expensive and
has a filament that is extremely sensitive
to shortened life because of a few hundredths
of an overvoltage. Additionally, its 25 watt
Grid Dissipation rating makes it vulnerable
if not sutably protected, to damage from
mistuning and arcs.
The 4-1000A being a Tetrode, is happiest being
Grid-Driven, but few amateurs have the inclination
to design and experiment with driving and neutralization
techniques, so many of these tubes end up Grounded Grid
at a miserable efficiency.
Additionally, the 4-1000A, with a 6KV at 1 Amp
anode requirement needs a power supply to suit, and
while transformers and diodes are plentiful, adequate
filter caps are not, and those that are available are
hellishly expensive once the array is gathered to
afford low ripple at maximum amperage.
Hal Mandel
W4HBM
