[Amps] Bill Orr comment

[Joe Subich, W4TV]

> I was reading the Bill Orr handbook and on his section about 
> amplifiers he says.....A properly designed grounded grid 
> amplifier should produce 2 to 2.5 times the plate dissapation 
> of the tube  in output.

Depends on what Orr means by the statement ... if he means that 
the output (amplifier + feed through power) will be at least 
twice the power dissipated in the tube, he's probably accurate 
at "two times."  If he means that a tube should be capable of 
producing 2.5 times its plate rated plate dissipation (e.g., 
1250 W in a 3-500Z or 3750 W in an 8877), he's mistaken or 
worse. 

For example an 8877 is rated for 1500 watts plate dissipation. 
Even at maximum HV (4KV) and maximum current (1A) - Eimac 
Absolute Maximum ratings - you will not see 3700 W output.  
Eimac's own data sheet shows only about 2KW at 3500V/1A.  

The calculations are similar for the 3CX800 - 2500V/.6A gives 
about 900 Watts out based on the absolute maximum ratings.  Even 
with Eimac's own data showing 800 mA for "short term duty" 1370W 
output is far less than 2X the 800W plate dissipation.  

Absolute Maximum ratings for a single 3-500Z are 4000V/.4A 
or 1600 W in.  With 65% efficiency, the output is barely twice 
the plate dissipation.  Eimac's typical operating conditions - 
3KV/.37A - shows 750W output or only 1.5 times rated plate 
dissipation.  

There may be tubes with lower rated plate dissipation that 
can be driven harder but these three examples say that Orr 
was over reaching with his statement. 

73, 

   ... Joe, W4TV 
   



> -----Original Message-----
> From: amps-bounces at contesting.com 
> [mailto:amps-bounces at contesting.com] On Behalf Of Gudguyham at aol.com
> Sent: Wednesday, July 23, 2008 12:30 PM
> To: amps at contesting.com
> Subject: [Amps] Bill Orr comment
> 
> 
> I was reading the Bill Orr handbook and on his section about 
> amplifiers he  
> says.....A properly designed grounded grid amplifier should 
> produce 2 to 2.5  
> times the plate dissapation of the tube  in output.  He did 
> not put  any 
> limitations on the statement as to IMD or anything like that. 
>  He did  not say if 
> the tubes ratings would be surpassed (I am sure they would), 
> but I  think what 
> he was saying is that the tube should continue to make power 
> to 2 to  2.5 times 
> it's dissapation before it would not make any more power and 
> flatten  out.
>  
> Upon speaking with an amp "Guru" about this subject, he 
> procalimed that  Bill 
> Orr was a "QUACK".  The basis of his claim was that he was 
> never able  to 
> build an amplifier that obtained that kind of results.
> What say you?  Lou W1QJ
> 
> 
> 
> **************Get fantasy football with free live scoring. 
> Sign up for 
> FanHouse Fantasy Football today.      
> (http://www.fanhouse.com/fantasyaffair?ncid=aolspr00050000000020)
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps