> Is there experience here with using 813 in triode connection?
Hello John,
The 813 is a very rugged tube and has the reputation of being
almost indestructable in amateur service. It is common to use it as
a triode. The main limitation of the 813 in conventional circuits is
reduced efficiency on bands above 20M.
ZL1AXB has successfully used a circuit which tunes the filament
and this improves the sfficiency dramatically. This tuned cathode
network takes the form of a bifilar circuit, and eliminates the
usual filament RF chokes. ZL1AXB demonstrates key-down >400W
output on 10m with a single 813 with Pv of 3000v.
The cathode circuit is described in an *Eimac* amateur service
newsletter #AS-6 by W6SAI, W6KEV, and W6UOV. Some of the material
may have appeared in QST August 1961 p16-21, but I have not checked
this.
Regards,
Martin ZL1ANJ
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