[Amps] 3CX1500D7 VS 3CX1500A7

[R.Measures]

>Compare the specs for the new 3CX1500D7 vs the 3CX1200Z. It appears that 
>it is
>a very similar tube with bigger cooler and
>filament designed to replace 3-500Z's. Downside is lower max frequency and 
>greater
>drive requirements. It may suffer ffrom lower output at 30 MHZ like the 
>3CX1200A7.

•    Lower output at 28 - 30 MHz is not the fault of the 3cx1200A7.  The 
problem is typically caused by using too little surface area for the tank 
L to compensate for skin-effect on the higher bands.    A good example of 
an amplifier with adequate skin-effect compensation is the TL-922.   Good 
examples of amplifiers without such are various Dentron amplifiers plus 
the AL-1200, and AL-1500.  
>
>
>In my opinion, the 3CX1500A7/8877 is a better tube for homebrew and new 
>applications.
>Lower drive requirements from the exciter mean lower IMD, potential greater
>efficiency at 30 MHZ, and much lower filament power requirements.
>
•  180-plus seconds warmup and a delicate grid are hardly pluses.  
However, for VHF, the 8877 is a better choice.  

>Dennis W0JX
>
>This message was written using Web Email from ACC http://www.accnorwalk.com
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