>
>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?
>
? The 8169 Ugly Amp shown on my website has a reed relay that reduces
filament voltage about 5% during Rx. Since the mains V decreases about
5% during Tx due to loading, there is virtually zero change in filament
volts from Rx to Tx. .
cheers, Pete
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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