[Amps] cathode to ground in tetrode amp

Sam's Mail kf4yox at earthlink.net
Mon Jan 30 13:12:04 EST 2006


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 at comcast.net>
To: <TexasRF at aol.com>; <Chuck_Partain at maxtor.com>; <dezrat1242 at ispwest.com>; 
<amps at 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 at contesting.com [mailto:amps-bounces at contesting.com] On
>> Behalf Of TexasRF at aol.com
>> Sent: Monday, January 30, 2006 12:10 PM
>> To: Chuck_Partain at maxtor.com; dezrat1242 at ispwest.com; amps at 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 at 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 at ispwest.com]
>> Sent: Monday, January 30, 2006  11:11 AM
>> To: Partain, Chuck; amps at 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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