807's vs 6146's as Modulator Tubes?

Glen Zook gzook at YAHOO.COM
Fri Sep 7 20:27:00 EDT 2007

The 6146W will work fine in the modulator.  However,
you may have problems in the T-150A using it instead
of the 6146 or 6146A/8298.

Any 6146W manufactured that has a code date of 1966 or
later (and some with a code date in the 2nd half of
1965) are the equivalent of the 6146B/8298A.  Those
manufactured before are the equivalent of the

Many transmitters designed for the earlier versions of
the 6146 have problems with the 6146B series.  Not all
transmitters because various individual examples of
any particular model work fine with the 6146B series. 
But, the vast majority of such transmitters usually
have problems with the 6146B.  It just seems to be how
the component tolerances "add up".  If you do use the
6146W in the T-150A be sure and neutralize and watch
the neutralization very closely for a while.  If the
tubes do not want to neutralize or if the
neutralization drifts you need to replace them with
either 6146 or 6146A/8298 tubes.  The 6293 can also be

Since you already have the 807 tubes I would just use
them.  Back in 1960 I built a plate modulator for my
original Globe Chief 90A using a pair of 807 tubes. 
It worked great even though I used a television power
transformer as the modulation transformer.

Glen, K9STH

--- kd4e <doc at KD4E.COM> wrote:

Will I notice any difference if I run a pair of 807's
OR a pair of 6146W's as the modulator tubes modulating
a pair of 6146W's in my Knight T-150A?
The modulator design is currently similar to that used
with the Viking and Valiant and other rigs of that
I'd prefer to use the same tubes in the modulator and
rig for the simplicity of keeping one type of power
tube in my backup drawer.

Glen, K9STH

Website:  http://k9sth.com

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