>From AA4LR:
> AM broadcasters and FM broadcasters generate many kW of power for their
> transmitters.
>
> Now, naturally, they use much bigger tubes in the final circuits than
> amatuer practice (and regulations!) permits, but what do they use to
> drive the big tubes? Don't they use something like a tube suitable for
> 1.5 kW in amatuer service?
>
> Or have these guys gone all solid state for their drivers?
--------------
New AM transmitters are mainly solid state, even 50+ kW. A few may still
use 3CX-series as modulators and 4CX-series as the RF PA. The drivers
are smaller versions of the same tubes, or are solid-state. AM solid state
technology does not scale well to the higher HF bands.
FM transmitters are still mainly tube PAs with solid-state drivers (but more
are solid state every year). They also use 3CX-series in grounded-grid or
4CX-series grid-driven.
TV is another animal. TV transmitters (VHF) use expensive specialized
tubes for maximum linearity in Class A operation. Solid state technology
is catching on strongly for both reliability and tube cost/availability.
There's nothing new here--ham amps use the tubes they do because they
were first used for commercial service!
HOWEVER..I have a couple of RF amp decks from an MRI machine to
play with if I ever get time...8 x MRF150 transistors, just like the Quadra
and PW-1! All set up for 1 kW from 20-80 MHz, but biased for pulsed
operation (needs modification).
How long before this type of surplus becomes common...???
73, Gary
K9AY
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