> >From what I understand the 3CPX1500 5.5v filament is a
> >PULSE SPEC. It is
> the same filament as in an 8877. The guy emailing REID,
> as that one too...
>
> It is ok with a directly heated cathode to turn down the
> filament until a
> noticed drop in emission, then turn it up a click...
You have to be very careful there.
It has to be at the very highest PEAK current at the lowest
anode voltage. If you set for a power drop at LESS than the
absolute peak cathode current for any band at the lowest
anode voltage it will be wrong. The peak cathode current
varies from band to band in an linear, so it isn't so easy
to waste your time trying gain nothing in life without
hurting IMD in amateur applications.
Of course those giving the generally bad advice to reduce
filaments below minimum ratings in amateur service often
give incomplete answers since they don't really understand
the full problem.
A broadcast station is a single-band single-anode-voltage
single-output-power single-mode situation and easy to do
right. Reducing voltage even, since the tube is run at a
fraction of ratings and not cycled off and on, improves life
in the 24 hour operation. In amateur service you would have
to measure the highest peak current condition to make an
adjustment that almost certainly will do nothing to improve
tube life.
> Not with an indirect full voltage
True. Run them AT the rating range. Nothing less. Just like
Hams should do for all tubes to be safe.
73 Tom
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|