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
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