[Amps] Schematics  for 4CX250B GG HF amplif ie r

[Bill Fuqua]

It may have served neither not both or either.
73
Bill wa4lav


At 08:30 PM 8/15/2012 -0400, Carl wrote:
>You cant have it both ways, either it has no purpose or its used to 
>prevent a parasitic. I vote for the latter and often there was one in the 
>screen and grid, right at the socket, in grid driven tetrodes that had 
>high gain well into UHF.
>
>Carl
>KM1H
>
>
>----- Original Message ----- From: "Bill Fuqua" <wlfuqu00 at uky.edu>
>To: "kc0hfl" <kc0hfl at cox.net>; <g8on at fsmail.net>; 
><JeanPierre.Behiels at electrabel.com>; <amps at contesting.com>
>Sent: Wednesday, August 15, 2012 8:06 PM
>Subject: Re: [Amps] Schematics  for 4CX250B GG HF amplifie r
>
>
>   I have seen this article before.
>There are two issues.
>One is the input circuit a T network and an inductor on the output.
>This does will not produce the best IMD. A capacitor between the cathode
>and ground would help.
>   But the real problem I have is the idea that the 100 Ohm resistor is
>necessary.
>It serves no purpose. Since there is no grid current the resistor can not
>produce a voltage drop.
>For some reason the author seems to think that is is necessary for plate
>current to flow.
>That is totally wrong.  In fact when operating class AB1 the max plate
>current in a tetrode is when
>the control grid is at the same voltage as the cathode and naturally the
>screen grid is at some fixed
>positive voltage.
>    When the tube is triode connected and the control grid is connected to
>the cathode, the
>screen grid becomes the control grid the roles are reversed. The screen
>grid swings to some
>maximum voltage, say 250 or 300 volts, and the control grid is zero. You
>get the same  results.
>Naturally, in grounded (screen) grid configuration just about all your
>drive will go to the output when
>using the 4CX250B.
>    The only thing the 100 Ohm resistor may have done is to snub out a VHF
>parasitic oscillation.
>
>73
>Bill wa4lav
>
>
>At 04:59 PM 8/15/2012 -0500, kc0hfl wrote:
>>http://home.comcast.net/~k7rld/4cx250bamplifier.htm
>>
>>Try the above.
>>
>>Bob
>>----- Original Message -----
>>From: "peter chadwick" <g8on at fsmail.net>
>>To: <JeanPierre.Behiels at electrabel.com>; <amps at contesting.com>
>>Sent: Wednesday, August 15, 2012 11:31 AM
>>Subject: Re: [Amps] Schematics  for 4CX250B GG HF amplifier
>>
>> > The 4CX250B is not suitable for use in the classic GG arrangement. Go to
>> > http://ahars.com.au/documents/eimac01.pdf  for an explanation.
>> > 73
>> > Peter G3RZP
>> >
>> >
>> >
>> >
>> >
>> > ========================================
>> > Message Received: Aug 15 2012, 04:03 PM
>> > From: JeanPierre.Behiels at electrabel.com
>> > To: amps at contesting.com
>> > Cc:
>> > Subject: [Amps] Schematics  for 4CX250B GG HF amplifier
>> >
>> > Hi guys;
>> >
>> > Anyone can help my with a full detailed schematic or documentation for
>> > building a HF grounded grid amplifier with 4 times a 4CX250B tube on > 
>> board
>> > ?
>> > All information will be mutch appreciated around this subject.
>> >
>> > Kindly regards Jean ON4AEF.
>> >
>> >
>> >
>> >
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