At 02:03 PM 9/28/2001 -0700, Steve Katz wrote:
> [Steve Katz] I realize that, although I have not made any
>measurements to confirm how effective this is. I'm questioning why Henry,
>Drake and others used centrifugal blowers and glass chimneys, at obviously
>increased cost and complexity, when these things are apparently not
>required. And my very old Eimac data sheets on a variety of power grid
>(glass) tubes recommends use with their glass chimneys. Was that just to
>sell expensive glass chimneys?
No, it was the technically correct way to do it. The tubes could be put
into continuous service in some application (drivers for an AM broadcast
transmitter for example) at 100% duty cycle, hence proper cooling was
absolutely required to provide reasonable life. Hence Eimac's recommendations.
The fan aimed across the envelope and filament pins work fine in amateur
service where the duty cycle is generally low, low, low. If you ran RTTY
for an hour or so at full output with the fan method, you might find the
limitations of that cooling method quickly.
> > As for cooling the tube glass envelopes, the high volume low pressure air
> > from these type fans wraps around the tube envelope and cools t very well.
> [Steve Katz] Seems to.
> > 73
> > Steve wd0ct
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