>
>
>----- Original Message -----
>From: "Douglas Snowden" <Douglas.R.Snowden@noaa.gov>
>To: <conrad.farlow@virgin.net>
>Cc: <amps@contesting.com>
>Sent: Tuesday, April 10, 2001 3:25 PM
>Subject: Re: [AMPS] MLA2500 and screen voltage for 4CX800.
>
>
>> OK Conrad - thanks for the feedback. I read what
>> you just said, but I don't understand why the screen
>> would have a problem. I vaguely remember seeing something
>> like this on a web site. Was it the measures page/s?
>> Of course, I guess if the plate voltage got very low, I
>> could see a problem developing.
>>
>> Doug N4IJ
>
>Hi Doug, if you read the Tech notes on the G3SEK page there is a technical
>explanation but basically ANY variation in screen voltage will wreck the IMD
>performance of a tetrode and thus produce socially unacceptable amounts of
>splatter.When you drive an amp with a complex varying waveform such as SSB
>the anode voltage will swing all over the place.Obviously if you are
>deriving your screen voltage from here your regulation will suffer. If your
>regulation suffers then so will other band users.
>
>http://www.vcnet.com/measures/D.a.08.GIF is the circuit to use off Rich's
>pages. He also has a stack of zeners off the plate supply on another
>page.Please don't do this.
>
It was not Rich's idea. Eimac recommends a shunt screen regulator for
smaller tetrodes. I used the circuit in two amplifiers and dynamic
screen V regulation was better than 1%. A caveat: Operate zeners at no
more than 33% of rated dissipation.
>
>Conrad G0RUZ
>
>
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>
>
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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