[Amps] Subject: grounding grids

[Joe Subich, W4TV]

> I am asking why he thought that, because we are talking about 
> the Drake L4 amplifier

No, we were talking about the SB-220 and the RF choke has such 
a high value (1 mH) that it is an open circuit compared to the 
capacitors. 

73, 

   ... Joe, W4TV 
 



> -----Original Message-----
> From: amps-bounces at contesting.com 
> [mailto:amps-bounces at contesting.com] On Behalf Of Gary Schafer
> Sent: Sunday, August 02, 2009 10:01 PM
> To: 'Herzog'; 'Ham-amps'
> Subject: Re: [Amps] Subject: grounding grids
> 
> 
> No red herring here. Joe made the statement that "the 
> impedance between grid and common changes by a factor of 10:1 
> between 3.5 and 29.7 MHz".
> 
> I am asking why he thought that, because we are talking about 
> the Drake L4 amplifier with the grid chokes and grid bypass 
> capacitors which are reported to be there to provide an 
> amount of negative feedback, over that frequency range. If 
> only the bypass capacitors impedance is considered then that 
> may be true. BUT, there is also a choke between the grids and 
> ground which will modify any constant change in impedance. 
> 
> 73
> Gary  K4FMX 
> 
> > -----Original Message-----
> > From: amps-bounces at contesting.com 
> [mailto:amps-bounces at contesting.com] 
> > On Behalf Of Herzog
> > Sent: Sunday, August 02, 2009 7:15 PM
> > To: Ham-amps
> > Subject: Re: [Amps] Subject: grounding grids
> > 
> > Since I subscribe to the general story that the grounding strap and 
> > internal connection to the tube acts as an inductor, the 
> impedance is 
> > = to a constant times the inductance times the frequency; 
> which is a 
> > ratio of about 30 to 3 MHz, or a ten to one ratio. I know that it 
> > would actually act as a complex transmission line, but 
> engineers like 
> > to simplify life.  Old slide rule mentality, etc.  K2LB Wil 
> > ==============================
> > RE:  What makes you think that the impedance between the grid and 
> > common changes by a factor of 10:1 between 3.5 and 29.7 MHz? 73
> > Gary K4FMX
> > =============
> > That is a red herring.  Because the frequency ratio is 
> about 10 to one
> > is the answer.
> >      This begs the question as to whether the impedance is 
> enough to care
> > about, and cap or inductive,  or a series resonance.  Such wonderful
> > considerations are why we can discuss this matter after 
> over 50 years.
> > Wil
> > _______________________________________________
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> > Amps at contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> 
> 
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