[Amps] SB-220 bias question

[Joe Subich, W4TV]

> If the amplifier was then used on SSB driven by a human 
> voice, the only time the amp would _not_ be mis-tuned is 
> when the human voice peak drove the amp to exactly the 
> same level as the peak of the tone used for tun-up.
> 
> That seems wacky to me.

No ... with SSB the plate load impedance is dynamic as 
opposed to static (a single value) with CW or RTTY.  For 
SSB or any other amplitude modulated emission, the 
calculation of plate load impedance includes the plate 
conduction angle and average (dynamic) Ep/Ip ratio.  

The tank (flywheel) effect of the output network smoothes 
the impedance swings. 

With On/Off keying or FSK, Ep/Ip is constant there is no 
dynamic variation.  


> -----Original Message-----
> From: jerome schatten [mailto:romers at shaw.ca] 
> Sent: Saturday, August 29, 2009 9:33 PM
> To: Gudguyham at aol.com; lists at subich.com; sub1 at rogerhalstead.com
> Cc: amps at contesting.com
> Subject: Re: [Amps] SB-220 bias question
> 
> 
> And by extension, consider an amplifier tuned with a steady tone for  
> maximum power out when the i/p side of the pi network matches 
> the tube  
> plate Z and the output of the pi matches the load Z. If the 
> amplifier  
> was then used on SSB driven by a human voice, the only time the amp  
> would _not_ be mis-tuned is when the human voice peak drove 
> the amp to  
> exactly the same level as the peak of the tone used for tun-up.
> 
> That seems wacky to me.
> 
> jerome - va7vv
> 
> On Sat, 29 Aug 2009 17:56:36 -0700, <Gudguyham at aol.com> wrote:
> 
> >
> 
> >
> > Fine, but none of those amps change the plate voltage in the
> > different
> > modes, so you mean to tell me they are designed wrong?
> >
>