I have built several grid driven tetrode amps, The cathode is grounded, The
screen does not go to ground through anything. The screen supply should be
shunt regulated to be able to handle positive and negative screen current.
Try Ian Whites web site for good information . If you care to build a grid
driven tetrode I suggest using his tetrode boards. Good luck Sam KF4YOX
----- Original Message -----
From: "Gary Schafer" <garyschafer@comcast.net>
To: <TexasRF@aol.com>; <Chuck_Partain@maxtor.com>; <dezrat1242@ispwest.com>;
<amps@contesting.com>
Sent: Monday, January 30, 2006 12:49 PM
Subject: Re: [Amps] cathode to ground in tetrode amp
> >From what I saw it is a conventional grid driven amp. The screen resistor
> >to
> ground is to prevent negative screen current from raising the screen
> voltage. The cathode resistor is obviously a mistake.
>
> 73
> Gary K4FMX
>
>> -----Original Message-----
>> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
>> Behalf Of TexasRF@aol.com
>> Sent: Monday, January 30, 2006 12:10 PM
>> To: Chuck_Partain@maxtor.com; dezrat1242@ispwest.com; amps@contesting.com
>> Subject: Re: [Amps] cathode to ground in tetrode amp
>>
>>
>> This schematic is a bit hard to read but it looks like the screens of the
>> tubes are grounded. If this is the case, then the cathode has to be above
>> ground
>> for d.c. by the screen voltage value. RF is another matter and
>> appropriate
>> bypass capacitors will take care of that.
>>
>> When the cathode is above ground for d.c. rf chokes are needed to help
>> isolate the rf from the power supplies (all three, grid, screen and
>> plate). The
>> cathode bypass C does most of this but an rf choke only helps.
>>
>> 73,
>> Gerald K5GW
>>
>>
>>
>> In a message dated 1/30/2006 10:14:38 A.M. Central Standard Time,
>> Chuck_Partain@maxtor.com writes:
>>
>> ya
>>
>>
>>
>> <http://www.angelfire.com/nb/ni4l/gu84b.html>
>> http://www.angelfire.com/nb/ni4l/gu84b.html
>>
>> Look down at the ONE tube schematic.
>>
>> This is the only one I have seen for HF so far that's not too
>> convoluted.
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: Bill Turner [mailto:dezrat1242@ispwest.com]
>> Sent: Monday, January 30, 2006 11:11 AM
>> To: Partain, Chuck; amps@contesting.com
>> Subject: Re: [Amps] cathode to ground in tetrode amp
>>
>>
>> ORIGINAL MESSAGE:
>>
>> At 07:14 AM 1/30/2006, Partain, Chuck wrote:
>>
>>
>>
>> OK, getting into this more and more every day and learning. Looking at
>> some
>> designs on this GU-84b
>> amp, I see a lot if not most of the cathodes have resistance, some a
>> lot(30k) some little (.7) to ground.
>> The screen grid and control grids are not grounded and have respectively
>> ~350 and -150v on them.
>>
>> Why wouldn't it just essentially go to ground? what does the R do in
>> series?
>>
>> thanks as always.
>>
>> KA1MWP
>>
>>
>>
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> Is there a schematic we could look at?
>>
>> 73, Bill W6WRT
>>
>>
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>
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