>The Drake L-4B has been characterized as a good amp with a marginal power
>supply. Are there any generally accepted mods to improve the power supply?
>
>73, Dick
IMO, Dick, raising the anode supply to 4kV will increase RF output by
about 2db and decrease the amount of drive power needed to produce 0.8A
of anode current. .Is 2db worth the effort? If the stock HV transformer
is kaput, yes. If you are ordering a Peter Dahl Hipersil transformer,
get at least two secondary taps so you can reduce v as needed for rtty,
cw, fm, am. Remember that there are several considerations in such a
modification--i.e., you don't just drop in a new transformer. If you
want more than 2db when the need for more suds arises, and you like to
build, consider a tetrode with handles.
If the anode v is increased on an L4, lower Rp VHF suppressors are
needed according to the people I know who have done the 4kV anode supply
mod.
Another useful mod would be high speed T/R switching. [see 1/94 QST,
"The Nearly Perfect Amplifier".
Rich---
R. L. Measures, 805-386-3734, AG6K
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