On Jul 20, 8:20 pm, Phil Kane wrote:
On Wed, 16 Jul 2008 20:51:14 EDT, wrote:
There are, such as RF power amplifiers for HF and low VHF. While it is
certainly possible to build the solidstate equivalent of, say, a
single-3-500Z HF amplifier, the SS version costs more and is less
efficient.

Yet the broadcast industry is going to SS as fast as they can.
Modular in design, if one "final" module fails, the power gets reduced
but they stay on the air. If a "final" tube fails, it's February
2009 much sooner. Reduction in maintenance costs outweigh capital
investment. I don't think that you can buy a new AM broadcast
transmitter below 50 KW that isn't SS all the way, and there are
plenty of SS 50 rigs in service.

Of course! But that shows the difference between Amateur Radio and
other services.

Perhaps I should have specified that the comparisons I was making were
between SS and tube amps meant for Amateur Radio service, particularly
HF and VHF service.

A broadcast transmitter has to be ultra-reliable and built for
continuous service. At 8760 hours in a standard year, it doesn't take
long for a component with an expected life of 10,000 or 20,000 hours
life to require replacement. Which BC folks tend to do on a schedule,
rather than waiting for failure to force the issue.

But with a very few exceptions, an amateur transmitter spends very
little time actually transmitting. I'd guess that most active amateurs
are on the air less than 1000 hours per year (that's about 2-3/4 hours
per day, every single day), and when they are on the air, most spend
at least half their time listening. OTOH, most amateurs will change
frequency at least once in a while...

So while the BC station owner can justify the purchase of an SS
transmitter based on lower maintenance costs, the amateur is usually
more limited by first-cost.

73 de Jim, N2EY