> 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@contesting.com
> [mailto:amps-bounces@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@contesting.com
> [mailto:amps-bounces@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
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
>
>
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