At 02:06 AM 12/31/00 +0000, David Kirkby wrote:
...
>
>There is a paper "Techniques to Extend the Service Life of High Power
>Transmitter Tubes" by the Voice of America technical department, in a
>PDF file on Burle's web site -
>http://www.burle.com/applicatnotepowertub.htm
>
>This shows that for the VOA at least, the reduction in tube failure rate
>by leaving on the heaters 24 hours per day was very significant. Tube
>costs at one site dropped from $420,00 per year to under $100,000 per
>year, with only an extra $15,000 per year in electricity costs. Their
>usage pattern is not typical of that of amateurs, and their tubes are a
>little larger. However, for me at least, is strong evidence to keep the
>heaters on.
Very interesting paper, Dave. I notice that an important part of VOA's
operating strategy is to keep the filaments at 80 percent voltage or so
during stand-by periods, and they state that at this level emission life is
expended at about 1 percent of the rate at full rated filament voltage.
Since most ham operation, particularly search and pounce DXing, is 80-95
percent "standby," we may be giving back some of the benefit of constant-on
by running the tubes at full operating filament voltage during these
periods. I wonder if anyone has ever tried reducing filament voltage on a
ham amp during standby conditions. Any reason not to?
Maybe K5PRO or someone else with big broadcast tube experience could
comment on how well VOA's strategy would apply to amateur tubes and
operating styles.
73, Pete N4ZR
Happy Holidays!
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