[Amps] Fw: "Tubes 201" - How Vacuum Tubes Really Work

[Will Matney]

Peter, I'm not denying that. However, you said it correctly, there is a potential differece because of a voltage drop across the choke. The grid becomes positive (less negative than the cathode) with respect to the cathode which is exactly right. However, the grid is still at 0 Vdc. That's what we have to look at here. Even biasing the cathode will produce the same result. Even though there's a potential difference between the cathode and grid, the grid is still tied to ground and holds it from ever going above 0 Vdc. I guess I should have added that to the scenario, but I was trying to have to type the least amount I had to.

Best,

Will

*********** REPLY SEPARATOR  ***********

On 7/25/06 at 9:15 PM Peter Voelpel wrote:

>Will,
>
>the RF drive in GG is developed directly at the cathode.
>The cathode choke forms a RF resistor in parallel to the tubes input
>impedance from cathode to ground.
>The positive going cycle develops a positive voltage to ground, the
>negative
>cycle a negative voltage across that resistance to ground.
>Therefore during the negative cycle the grid becomes positive with respect
>to the cathode and large grid current is drawn.
>
>73
>Peter
>
>
>-----Original Message-----
>From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
>Behalf Of Will Matney
>
>I should have added; On that, I agree it's the only way to make one
>positive
>(for only part of a cycle on a grid driven biased grid). A grounded grid,
>cathode driven, cathode at ground potential tube though, I can't see the
>grid being positive. Here, the electrons flowing through the tube is varied
>by the signal, and those same electrons are what travels to the grid to
>charge it. In this case, the grid is being bombarded by electrons. If the
>grid was less negative, it world attract electrons until a balance was
>reached then repel them. The voltage on the grid could never raise above 0
>Vdc as I see it.
>
>Best,
>
>Will
>
>
>*********** REPLY SEPARATOR  ***********
>
>On 7/25/06 at 2:15 PM Will Matney wrote:
>
>>Peter,
>>
>>On that, I agree it's the only way to make one positive (for only part of
>>a cycle). Are there any other ways to make the grid positive and the grid
>>be at ground potential with the cathode at ground? A lot of amps cathodes
>>are at ground potential unless biased.
>>
>>Best,
>>
>>Will
>>
>>
>>
>>*********** REPLY SEPARATOR  ***********
>>
>>On 7/25/06 at 8:04 PM Peter Voelpel wrote:
>>
>>>Nothing is easier then that if the cathode is going/driven negative with
>>>respect to ground.
>>>Grid voltage is always measured from grid to cathode, not to ground.
>>>
>>>73

>>>Peter
>>> 
>>>
>>>-----Original Message-----
>>>From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
>>>Behalf Of Will Matney
>>>
>>>please explain how a grid becomes positive when tied to ground?
>>>
>>>
>>>
>>>_______________________________________________
>>>Amps mailing list
>>>Amps at contesting.com
>>>http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>>
>>_______________________________________________
>>Amps mailing list
>>Amps at contesting.com
>>http://lists.contesting.com/mailman/listinfo/amps
>
>
>
>_______________________________________________
>Amps mailing list
>Amps at contesting.com
>http://lists.contesting.com/mailman/listinfo/amps
>
>_______________________________________________
>Amps mailing list
>Amps at contesting.com
>http://lists.contesting.com/mailman/listinfo/amps