Hi Gary, thanks for your reply.
Yes, I was around when regulations were based on input power (1968) and have
heard your explanation before but I tend to question it simply because the
Henry 3K and 8K series of amps also came stock with the CW/SSB selection and
either of those two could easily exceed 1000 watts DC input in the CW
position. FSK and AM modes were also advised to use CW and not SSB modes
possibly with plate dissipation limits in mind as well as legal issues of
input power.
But based on the typical pair of 3-500's say in the 3K original designs, in
CW mode idling current was 90-120 ma, and in the higher plate voltage SSB
position 170-220 ma.
My logic was simply:
Bias controls the class of amplifier.
A change in bias means the class of amplification must have also changed.
Switching from CW to SSB causes an indicated bias change from 120 ma to 220
ma.
The impact of a bias change of 120 to 220 ma would lead me to believe that
the class of amplifier shifted slightly in a more linear direction with also
the result of slightly lower efficiency.
Right or wrong or maybe just trivial ... if wrong could you please explain
your logic?
Mark
Wa3jpy
-----Original Message-----
From: Gary Schafer [mailto:garyschafer@largeriver.net]
Sent: Wednesday, October 30, 2019 10:13 PM
To: 'mark bitterlich'; 'Joe Subich, W4TV'; 'Joe'; amps@contesting.com
Subject: RE: [Amps] SB-220 HV Transformer Wanted
No. The amp runs AB2 meaning it draws grid current.
The reason for the CW/SSB switch was to allow tune up at 1 KW DC input on
CW.
This was the regulation at the time the amp was designed. You were not
allowed to ever exceed 1 KW DC input, even during tune up.
Switching to SSB after CW tune up allowed higher PEP input by maintaining
the same plate load impedance (where the amp was tuned)for the higher power.
In other words the voltage to current ratio remained the same when the
higher voltage was selected.
73
Gary K4FMX
> -----Original Message-----
> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of mark
> bitterlich
> Sent: Wednesday, October 30, 2019 4:23 PM
> To: Joe Subich, W4TV; Joe; amps@contesting.com
> Subject: Re: [Amps] SB-220 HV Transformer Wanted
>
> Ok, this brings up a technical question that pertains to the topic
> amazingly enough. When you shift from single sideband to CW on this amp
> are you or are you not moving the class of operation from AB1 towards
> AB2 and thus improving efficiency?MarkWA3JPY
> -------- Original message --------From: "Joe Subich, W4TV"
> <lists@subich.com> Date: 10/30/19 16:36 (GMT-05:00) To: Joe
> <nss@mwt.net>, amps@contesting.com Subject: Re: [Amps] SB-220 HV
> Transformer Wanted On 2019-10-30 3:12 PM, Joe wrote: > Why need
> them?Some people prefer to keep their equipment "stock" or at
> leastfunctionally stock. The SB-200 was never designed for 1500Woutput
> on CW - it was designed to operate at 1 KW DC input (ca.700 W CW or 1500
> W PEP SSB output).Pushing the SB-220 to 1500 W CW output (or worse,
> running RTTYon the high taps) is a quick way to fry something. Even
> thetoroidal transformer you recommend is only rated for 800 W!73, ...
> Joe, W4TVOn 2019-10-30 3:12 PM, Joe wrote:> Why need them?> > Run it at
> the HV side and use less drive and less currents all around.> > The
> CW/SSB switch I converted into a stand-by switch.> > Joe WB9SBD> Sig>
> The Original Rolling Ball Clock> Idle Tyme> Idle-Tyme.com>
> http://www.idle-tyme.com> On 10/30/2019 1:38 PM, Joe Subich, W4TV
> wrote:>>>> >> https://www.antekinc.com/as-8t800-800va-transformer/>>>>
> Unfortunately, this transformer lacks the primary taps for CW/SSB>>
> operation of the OEM device.>>>> 73,>>>> ... Joe, W4TV>>>>>> On 2019-
> 10-30 10:23 AM, Joe wrote:>>>>>> On 10/30/2019 8:56 AM, Joe wrote:>>>>
> Morning Dick,>>>> If you are not afraid of making a few electrical and
> mechanical >>>> modifications, I would go with this transformer.>>>>
> https://www.antekinc.com/as-8t800-800va-transformer/>>>>>>>> I'm glad I
> did! 1/4 the cost of most drop in replacements. yet MUCH >>>> better
> performance!>>>> Joe WB9SBD>>>>>>
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