[AMPS] Electronic Bias Switching

[Paul Christensen]

As I was searching through the database of my new QST collection on CD-ROM,
I found an interesting suggestion from an old acquaintance and mentor of
mine, Barry Boothe, W9UCW of "The Minooka Special" fame.

In a mid-70s issue of QST, Barry describes a unique method of implementing
EBS to his homebrew amp.  Rather than employ bias to the cathode, as is
common in the ETO line of Alpha amps and perhaps others, he applies bias to
the control grid in a GG configuration, by placing a pair of 0.01 uF mica
from the grid to ground, and impresses negative bias to the control grid
with the commonly-found darlington transistor pair who's bias is driven from
the amp's input RF sample.  From an R.F. perspective, the tube remains
grounded, yet allows for D.C. bias.  It's a single-state switch, but the
point to be made is that EBS bias is applied to the grid rather than the
cathode, thus eliminating the need for complicated protective measures
between the EBS circuit and the cathode.

Has anyone on this list attempted to implement EBS control in this manner
and if so, how successful was it?  Thanks.

-Paul, W9AC



--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm