Mike Waters wrote:
How about adding a tertiary winding to the step-up transformer, and use
that for the out-of-phase neutralizing signal? One end of the winding to
ground, the other end to a neut. capacitor connected to the plate?
You may be right on the requirements of the drive signal to the swamped
grid. I have a couple of ideas there.
The thing about 833s boils down to when 1 kW INPUT was the rule, 813's
were available for $5 to $15 NOS each and a pair in P-P using B&W 1 kW
coil sets worked 160 to 10 meters class "B" for 1 kW in. (look in
handbooks published before 1955)
833s were used in older (from the 40's) broadcast transmitters with no
fans or blowers for 500 and 1,000 Watts unmodulated carrier out with long
life and trouble free operation. The power capacity of the 833 was just
not necessary for HAM HF operations. One tube giving you 500 Watts was
frequently done, but only where GOOD pulls were available, few radio
stations stations using 833s removed a GOOD tube, unless a HAM worked
there and wanted a free used tube. 4-400s are in the same category, just
different transmitter makers.
--
Ron KA4INM - Youvan's corollary:
Every action results in unwanted side effects.
Many hams have always run over the legal limit and a single 833 is
equivalent to a pair of 813's power wise. Their service life was no
different than most any other tube in BCB service. When RF output dropped
they were swapped with the pair in the modulators and when the modulator
current dopped they were finally replaced. They either went to hams or
scrap.
Running a pair of 250TH's were more common on the ham bands due to surplus
availability and a very common socket, plus they worked a lot better at 20M
and up. The 304TL, 450TH and 6C21 were also used and later a pair of
4-400A's or the 4-1000A were everywhere.
Carl
KM1H
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