[[AMPS] Tetrode poor IMD performance ]

[2]

>
>Expanding a bit on what Paul Christensen wrote - going to the review of 3 
>amps
>in QST, Sept 1997, and 4 others in July 1992:
>
>Alpha 91b          GU-74B/4CX800A       AB1      3d/5th ord IMD: 45/49 dB 
>
>Ameritron 800H     3CX800               AB2       "  "   "   " : 49/55 dB
>
>QRO HF-2500DX      GU-74B/4CX800A       AB1       "  "   "   " : 43/40 dB
>- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>Ameritron AL-82    3-500Z                         "  "   "   " : 38/54 dB
>
>Commander HF-1250  3CX800A7                       "  "   "   " : 48/44 dB
>
>Kenwood TL-922A    3-500Z                         "  "   "   " : 38/54 dB
>
>Ten-Tec Centurion  3-500Z                         "  "   "   " : 38/50 dB
>
>Looks like there is much more involved in the variation than whether a
>grounded-grid triode or a tetrode design is used.  I won't venture guesses as
>I'm not that conversant in amp design and the many tradeoffs.  Reflecting on
>the list, though, maybe ceramic is better than glass - nah, I won't go 
>there! 

//  With typical transceiver IMD in the low -30s range, the typical 
amplifier adds no noticable distortion.  

cheers, Duane
>
>
>"Tom Rauch" <w8ji@akorn.net> wrote:
>
>Hi All,
>
>Does anyone have any idea why tetrode amps like the one just 
>reviewed in QST seem to have such poor IMD performance?
>... etc....
>
>Duane Calvin, AC5AA
>Austin, Texas
>
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>


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


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