So in other words it's not a technical issue so much as it is a "idiot proof"
fail safe measure?
Many operate the SB-220 on RTTY and digi modes where the CW position is a key
to transformer survivability.?
?
The same for 12/17M where the tank circuits are far from optimum and bandswitch
arcing can occur at 1200W.?
?
Some owners are a bit slow in tuning up and the CW position reduces the plates
from brilliant orange to a darker version.?
?
Carl?
KM1H?
-----Original Message-----
From: Carl <km1h@jeremy.mv.com>
To: Gudguyham@aol.com; amps@contesting.com
Sent: Sat, Aug 29, 2009 9:00 am
Subject: Re: [Amps] SB-220 bias question
Many operate the SB-220 on RTTY and digi modes where the CW position is a key
to transformer survivability.?
?
The same for 12/17M where the tank circuits are far from optimum and bandswitch
arcing can occur at 1200W.?
?
Some owners are a bit slow in tuning up and the CW position reduces the plates
from brilliant orange to a darker version.?
?
Carl?
KM1H?
?
?
----- Original Message ----- From: <Gudguyham@aol.com>?
To: <amps@contesting.com>?
Sent: Saturday, August 29, 2009 7:09 AM?
Subject: [Amps] SB-220 bias question?
?
> It was always my understanding with the SB-220 and other older amps that?
> the reason for lowering the plate voltage on the 3-500's or whatever tube,?
> was to comply with FCC regulations. Years ago the rule was 1KW DC input > CW?
> and 2KW PEP input SSB hence the change in plate voltage. Now that this > rule?
> has changed I was thinking. It is my observation that the 3-500 tube?
> performs much better with 3000 or more plate voltage, tube makes nice > power?
> with lower grid current for the same power at a lower plate voltage. > Hence,?
> my idea.?
> I routinely use 7 1N5408 reversed diodes to replace blown zeners.?
> Expanding on that idea I was thinking of removing the power transformer >
> primary?
> windings from the CW/SSB switch and wire nutting the wires together that?
> produce the higher plate voltage, then making up a small perf board with?
> about (have to experiment) 11 diodes and using the CW/SSB switch to short >
> out 4?
> of the diodes on CW to lower the idle current and have normal SSB idle?
> current when switched to SSB. That has been the modern day approach to > this?
> on the newer amps since the FCC ruling has changed. Many hams I know > went?
> to running CW with an SB-220 and other older amps in the SSB mode anyway.?
> Thoughts? 73 lou?
> _______________________________________________?
> Amps mailing list?
> Amps@contesting.com?
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