[AMPS] tuning capacitor & insulator

[Rich Measures]

>
>
>
>On Fri, 18 Dec 1998 10:54:06 -0800 Rich Measures <measures@vc.net>
>writes:
>>John Fielding wrote -- 
>>>>What's the difference?
>>>
>>Carl Heuther, KM1H, wrote -- 
>>>The 250R has a minute (Eimacs word) .2pf increase in output C over the
>>>7580. Both have a higher perveance than the 250B and require a 
>>slightly more negative bias voltage.
>>>At 1500V Ep any version can be made moderately clean. At 2000V they 
>>>are horribly dirty. 
>>
>>Ä  Carl:  .  By looking at any of the constant-current curves, one can 
>>
>>see that the closer the instantaneous anode/plate voltage comes to the 
>>screen's supply.V, the greater the departure from ideal straight-line 
>>linearity.   On Eimac's  constant-current curves for a screen 
>>potential of 400v for the 7580]4cx250R, the curve for 1.2a is quite flat 
between 
>>2000v and 600v.  Thus, with a supply potential of 2000v,  1400v of 
>>rather linear movement in the instantaneous anode potential is possible.  
>>However, if a 1500v supply were used, only 900v of linear movement in 
>>instantaneous is possible, and the most linear part of the curve 
>>between1500v to 2000v is lopped off.  How could eliminating the most 
>>linear part of the curve make the tube "horribly dirty"? 
>>-  cheers, Carl
>
>Since you believe what is published Rich ( when it is convenient ) how
>come you cant  agree with published Eimac results? 

€  Eimac said that linearity improved when the anode supply voltage was 
decreased from 2000v to 1500v?

>I also tend to disbelieve claims that I can not verify with HP quality
>test equipment. You make a lot of claims that I can not verify here with
>a similar amp. 
>The consensus from several continents appears to agree that the
>7580/4CX250R is dirty at higher Ep. Why do you always want to play word
>games and ignore some basic facts supported by measurements?

€  When alleged measurements do not agree with what one sees on the 
constant-current curves, my guess it is that problem is not in Eimac's 
curves.  
 -  Have you tested a 4cx250R with 400v on the screen and 2000v on the 
anode?   
>
>Please, dont repeat the old canned drivel...try something new for a
>change. You are beginning to sound like ur old buddy ...

€  If you are speaking about Mr. Rauch, he seemed to get moderately 
perturbed by the information I obtained from Eimac's constant-current 
curves when he was trying to convince us that high-Mu triodes could be 
successfully operated as linear amplifiers in Class AB1/grid-driven 
service.  
>
-  later, Carl


Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm