Will writes:
> What if you had two final tubes, one idle until the other
> gave up the ghost. It's easy to change over the same way with
> way less circuitry.
The cost of a "hot standby" transmitter using vacuum tubes is
far higher than just the tube alone. It really is a completely
separate transmitter with the exception of, perhaps, the low-
level stages. In television, since pre-correction adjustments
(linearity) generally need to be set up based on amplifier
tuning, it is far better to 'marry' a low level stage and
final amplifier.
When one considers the relatively small premium for solid-state
TV transmitters at low/high VHF and in some cases lower UHF,
tubes did not make a lot of sense in the last equipment replacement
cycle.
Now, with HDTV's (digital TV) 12 to 16 dB peak to average ratio
and the need to make up to 60 KW average output in some cases,
specialized tubes have reasserted themselves at UHF (though I doubt
any ham rig will ever use a multi-depressed collector Inductive
Output Tube - MDCIOT).
73,
... Joe, K4IK
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|