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VK6ZRT > HISTRY 09.11.07 09:24l 40 Lines 1505 Bytes #999 (0) @ WW
BID : 16261_VK6ZRT
Read: GUEST
Subj: Valves types of old
Path: ON0AR<VK6HGR<VK6ZRT
Sent: 071109/0823Z @:VK6ZRT.#BUN.#WA.AUS.OC #:16261 [Boyanup] $:16261_VK6ZRT
From: VK6ZRT@VK6ZRT.#BUN.#WA.AUS.OC
To : HISTRY@WW
When I first started working with valve transmitters there
were a few good line ups of tubes used.
The old AWA AM transmitters used the follwing,
RF stage, 807 oscilator, 807 Buffer, 828 driver driving a pair
of 833a in parralel as the output tubes.
In the audio stage there was 2 807 driving 2 810 driving a pair
of 833a's in pushpull to the mod transformer.
One of the other tx's had a pair of 4-1000 in pushpull as mod
on a 4-1000 output tube, all glowing red on the anodes.
Some of the tubes I have dealt with over the years were,
Klystrons, Magnetrons and Traveling wave tubes.
One of the oddest tubes was a Tochatron (no joke) it was an early
form of counting tube with 10 or 12 grids and anodes and was used
to randomly change frequencies on the radar.
The radar had a very strange output tube called a twystron, it was
a cross between a klystron and a traveling wave tube, it could put
out 5 Megawatts peak pulse power near 2 GHz the anode was at earth
and the cathode was pulsed to -28Kv to make it work, the trigger
tube was a klystron that was about a foot round and about 1 1/2 ft
tall, all of this was inside a lead case because it generated low
level Xrays as well when it was working.
Sadly these days everthing is going solid state and soon all of the
valve transmitters in the broadcast world will dissapear, tubes are
not cheap anymore and most valve transmiiters fail EMR testing so
they have to be replaced.
Ah memories.
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