Carl wrote...
< snip >
> I modified the HF and 6M NCL-2000's Ive had since 64-65 for individual bias
> adjust back then. A delta of around 5V is tolerable before IMD starts to
> suffer from the lower value biased tube being easier to drive. With static
> matching and a single adjustment a pair within 1V was considered matched.
>
> Ive deliberately kept far away from Russian tubes so cant say what their QC
> is like. However if Alpha is making such a fuss over it Id suspect that they
> vary considerably.
I have a bit of experience with the Russian tubes. I was surprised by how
different
the bias requirements for the tubes can be. I have measured variations in grid
bias
voltage of over 20 Volts to produce a given anode current (at constant screen
voltage
and anode voltage) .
Or as Carl correctly suspects, "...they vary considerably."
However, when the bias was adjusted to give the desired resting anode current,
the
performance was very similar.
73,
George T Daughters, K6GT
CU in the California QSO Party (CQP)
October 2-3, 2010
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