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[AMPS] Tetrode poor IMD performance

To: <amps@contesting.com>
Subject: [AMPS] Tetrode poor IMD performance
From: 2@vc.net (2)
Date: Thu, 16 Aug 2001 10:16:08 -0700
>
>Rich said:
>
>"It seems a bit doubtful that the 4CX1000A has c. 100-times as much 3rd
>order distortion as a 4CX1500B"
>
>The data I mentioned regarding the 4CX1000 and the 4CX1500 comes from:
>
>Care and Feeding of Power Grid Tubes copyright 1967 by Varian - Thrid
>Printing 1978.
>
>On page 64, under the heading 4.3 "Selection of Tubes for Single Sideband
>Service", it is stated that "As a guide in selecting tubes for various power
>levels of single-sideband service, typical operating conditions for various
>EIMAC tubes are included in this section.  ... Typical third and fifth-order
>intermodulation distortion product levels for maximum drive conditions are
>also given for the two-tone condition.
>
>In the "guide", I found the following information.
>
>4CX1000A/K @3000 volts yields -23 db 3rd order and -26 db 5th order
>distortion
>
>4CX1500B @ 2900 volts yields -44 3rd order and -48 db 5th order distortion.
>
>I did not make this stuff up, Rich.  I just reported it.  Don't shoot the
>messenger if the data does not fall into line with your preconceived notion 
of reality.

Your report is ver batim, Colin.  The sicky wicket is Eimac's data.  I 
have seen other errors they made,  

>
>On page 22.52 of the 23rd Radio Handbook, edited by William I. Orr, there is
>a  4CX1500B amplifier construction article.  In that article, the following
>language appears: "The linear amplifier described in this section is a
>deluxe 2-kw PEP, class AB2 grid-driven amplifier using the low distortion
>4CX1500B tube.  This is a ceramic-metal, forced-air cooled tetrode having a
>maximum plate dissipation of 1500 watts.  It is designed for exceptionally
>low intermodulation in SSB service."
>
>I knew one ham who ran a 4CX1500B and it was the cleanest amp I ever heard.

//  'tis so clean it makes today's radios look feculent.  

>I just wish a local ham - who runs a 4-1000 driven by an overdriven SB-200,
>ran a 4CX1500B operated properly.  Unfortunately, my antenna is larger and
>taller and his only way to combat that is to turn up his mike gain.  I
>expect he has had splatter reports from at least 100 countries - which would
>entitle him to the coveted DXCCS award.
>
//  Guffaw. 
 In days of yore, when I was active on 80m long-path, there was a turkey 
in LA who ran an obnoxiously overdriven (160w) SB-200.  He would make 
longish calls in hopes of getting through the sunup pileups.  This kept 
others from hearing the Europeans.  To assist this person in getting 
through pileups, someone with a tetrode-with-handles amplifier would 
deliberately double with the feculent station and say "silver dollar" - 
the offender's callsign suffix.  If the European station cold hear the 
14kW signal in the pileup , he would pick up the feculent station and, 
with luck, peace would temporarily return to c. 15kHZ of the DX window.  
Was this ethical?  At the time, I was a member of the American Radio 
Relay League, so why not?  

cheers,  Colin

-  R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.  
end


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