On 6/7/25 02:52, Bret Busby wrote:
It is all relative...
Yes it is, but you would be amazed at the supposedly intelligent people
who will argue the a 5 foot long low uhf band klystron amplifier as used
until the 1985 time frame, is immune to E=MV2 math.
extremely off topic, but possibly educational:
It can be a very high gain amplifier, turning a 1 watt drive at the top
of the tube into 30kw at the bottom, nominally 5 feet away. But the
output has a horrible time vs power level distortion. We did not then
know, and most assumed a non-linearity in the amplitude domain, but it
was actually in the time domain because the electron beam was traveling
at a voltage differential of 19,700 volts, the variable mass of the
electron changed because it could be slowed at the lower mass but
speeding it up raised the mass, so the average velocity was reduced,
increasing the transit time by around 120 nanoseconds at 30kw (ntsc sync
tips) vs 1kw (at ntsc white.) This put horrible spikes on both edges of
the sync.
At that time we did not know how to predistort the drive to compensate
that in the time domain but obviously we have learned how now or we
would not have our working hidef digital tv we have today.
I am glad that tech has been replaced with better stuff as the klystron
amplifier has a hell of a power bill, needing 113kw of wall power per
tube.. Do able when electricity was 2 cents a kwh, at 20 cents most
early uhf stations went dark, squeezed by the power bill into
bankruptcy. That and a tired tube was about $125,000 for a fresh one.
Certified check no time payment plan.
..
Bret Busby
Armadale
West Australia
(UTC+0800)
Cheers, Gene Heskett, CET.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
