[Amps] RF parts and parasitics!!

[Bill, W6WRT]

ORIGINAL MESSAGE:

On Wed, 26 Aug 2009 12:54:06 -0500, "Gary Schafer" <garyschafer at comcast.net>
wrote:

>
>If drawing a conclusion from a test you must first have the proper test
>setup with the proper equipment. Using an SWR bridge to determine if the
>input impedance of the tube is constant is not the right equipment.

REPLY:

I disagree. An SWR bridge will indeed show the AVERAGE impedance over the RF
cycle, whether drawing grid current or not. 

W8JI's statement was that when grid current is NOT drawn, the cathode-grid
impedance is very high. Since without grid current, the cathode-grid impedance
is essentially the SAME over the RF cycle, an SWR bridge will indeed show that
the input impedance is still low even with no grid current. That was my point.

73, Bill W6WRT