>Answer Not much The 3CX-3000A7 is notorius as being a Pig to drive. >The
>spec sheet states that 410 watts is required to drive it to 2.0 >Amps of
>plate current. With 100 watts don't expect much more than 500 >mils of
>plate current with the tube biased correctly.
While it is a pig to drive, 400 watts of input should net you quite a bit of
output. And he should be able to get legal limit from a typical 100 watt
exciter.
>As to 10 meters not tuning that is also predictable. The 3000 has an
>inordinately high output capacitance. 38pf Compare this to the 8877 >and
>4CX-1500A which each have values of 10 pf and its understandable >that you
>are not able to tune 10 meters.
Easily fixed.
Place a small amount of L in the lead from the tube to the tune c. This
will cancel out some of that 38 pF.
>Finally the plate voltage that you state you are using (6700 volts) is >a
>full 33% over the manufacturers Maximum recommended Plate Voltage of >5000
>Volts. BE CAREFUL !
The 3CX3K can take this amount of plate voltage without much whining. It is
a tube that has major amounts of overhead, as is the solid state 2SC2879.
>It appears that Eimac intentionally developed this tune with the >objective
>of keeping it out of the hands of Hams and CBers. My >recomendations, if
>you have this Amp running on all bands but 10 >declare victory and leave it
>alone. Drop the Plate Supply to 5000 >volts and limit the service of this
>amp to 14 Mhz and below.
Having built, tuned and operated single and dual 3CX3K amplifiers on 27
megaherts, I can tell you it can be done.
at your level of plate voltage, expect about 10 to 12 thousand CB watts out
of the thing, but you need to get your plate tank circuit correct.
Also, what kind of input network are you using?
--Toll Free
The CBer Extraordinairre
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