Peter Voelpel wrote:
>>David is right. 4CX1500B seems to be just 4CX1000A with declared 500W extra
>>dissipation at the expense of the air flow.
But also a different anode cooler with a genuinely higher dissipation.
>>The grid and screen however are
>>same - very fragile. That's why it can't produce more output.
>>But the puzzle is why Eimac specifies it with even less output power than
>>4CX1000A?
>That less output is caused by the load line used with Eimacs specification
>which is more A then AB1 resulting in lower efficiency and lower
>intermodulation distortion.
That's right. The 1500B would produce as much output as the 1000A if
Eimac had chosen to specify different operating conditions.
Recommended operating conditions are a matter of *choice* on the part of
the manufacturer. Power output and efficiency have to be balanced
against IMD in response to market demands.
When reading an Eimac data sheet, never underestimate the power of their
Marketing Department. The power struggles between Engineering and
Marketing were legend, and the tube data sheets were their
battle-ground.
Back in the 1960s, the recommended operating condx for the 1000A were
optimized for raw output power; IMD isn't even mentioned on the data
sheet. But by the mid-80s, the market was demanding low IMD. Eimac's
response with the 1500B was to change the recommended load lines to
improve the IMD, just as Peter describes, and the available output power
reduced accordingly.
The efficiency was also reduced, so the anode dissipation was increased
to 1500W by simply specifying more airflow! But "1500" looks so much
better than "1000", right?
>The 4CX1500B however can be driven harder then the 4CX1000A as grid
>dissipation is one watt compared to zero on the latter.
The *physical* power dissipation of the 1000A grid cannot be literally
zero. Eventually Eimac changed the data sheet to allow up to 5mA of grid
current to flow "for peak signal monitoring purposes"... but for some
reason the maximum rated power dissipation has always remained at
literally "zero".
--
73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek
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