[Amps] SB-220 bias question

[Bill, W6WRT]

ORIGINAL MESSAGE:

On Sat, 29 Aug 2009 09:00:46 -0400, "Carl" <km1h at jeremy.mv.com> wrote:

>
>Many operate the SB-220 on RTTY and digi modes where the CW position is a 
>key to transformer survivability.

REPLY:

The real key to transformer survivability when running RTTY is the amount of DC
plate current drawn. The transformer does not care which position the bias
switch is in. 

If you pay very close attention, you should find that for a given DC plate
current, you will get a whisker more power with the switch in the CW position
because biasing the tube closer to class B is a bit more efficient. The
difference is small and you might not even notice it if you weren't looking for
it.. 

Bottom line: Watch the plate current. That is the key to making the transformer
last a long time. 

73, Bill W6WRT