Fuqua, Bill L wrote:
> Let see. RF plate voltage is proportional to RF plate current,,,,RF cathode
> current is proportional to plate current....RF voltage across the cathode
> drive impedance is proportional to RF cathode current and the cathode drive
> impedance which is equal in magnitude to the tubes input impedance, if
> everything is matched. The RF cathode to grid voltage is in phase with the RF
> plate voltage The grid-cathode RF voltage is 180 degrees out of phase with
> the RF plate voltage.
>
> Sounds like negative feedback to me.
> And it is. That is why a small additional resistance in series with the
> cathode improves IMD and decreases the gain.
>
and should reduce the need for carefully balancing the tubes.
73
Roger (K8RI)
> 73
> Bill wa4lav
>
> ________________________________________
> From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf Of
> Gary Schafer [garyschafer@comcast.net]
> Sent: Thursday, July 30, 2009 12:09 AM
> To: dezrat1242@yahoo.com; amps@contesting.com
> Subject: Re: [Amps] grounding grids
>
>
>> -----Original Message-----
>> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
>> Behalf Of Bill, W6WRT
>> Sent: Wednesday, July 29, 2009 10:29 PM
>> To: amps@contesting.com
>> Subject: Re: [Amps] grounding grids
>>
>> ORIGINAL MESSAGE:
>>
>> On Wed, 29 Jul 2009 21:35:47 -0400, "Joe Subich, W4TV" <lists@subich.com>
>> wrote:
>>
>>
>>> Unfortunately, as shown by others this is not accurate and since
>>> the negative feedback varies significantly from band to band the
>>> floating/bypassed grids simply can't work as Heath claimed.
>>>
>> REPLY:
>>
>> Also, that isn't true negative feedback anyway. It is just gain reduction.
>> True
>> negative feedback means taking a sample of the output, inverting the phase
>> (if
>> needed), and feeding it back to the input.
>>
>> 73, Bill W6WRT
>>
>
> How then would you account for the reduced IM products of a tube operated in
> GG verses the same tube operated in a standard grid driven configuration?
>
> 73
> Gary K4FMX
>
>
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>
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