[AMPS] 8930 Idling and Maximum Plate Current ( AM-6154/55 )

[2]

>
>Can anyone tell me what they are using for Idling and Maximum Plate Current 
>on the 8930 Tube for use in a VHF/UHF Amplifiers ( specifically AM-6154/55 
>type amplifiers ) . Eimac claims maximum plate current rating at 250 ma ..  
>The specification claims idling current at about 90 ma for SSB operation. I 
>am using it in the CW mode most of the time. I also notice when I key the 
>amp 
>up, I still get linear power ( not saturated ) as high as 500 ma without 
>saturation at the output but worry about burning out the tube ( many people 
>claim they can run 450 watts out of this tube with no failures, ( I wonder 
>if 
>this has something to do with the plate current being run well above 250 ma 
>???) . I also notice the specification rates the tube as high as 500 ma in 
>the " AB1 AF Amplifier / Modulator " type of operation which leads me to 
>believe that Eimac claims it can operate with this high of plate current.
>
500mA is for 2-tubes. 

>Any comments appreciated  ( I am still learning about high power 
>amplifiers  )
>
The 8930 is a 4CX250R with a larger anode cooler.  I used to run a pair 
of them on 2m SSB in AB1with 400 screen V and 2400 anode V.  With such 
potentials, one can exceed the 250mA/tube rating without drawing grid 
current. To avoid exceeding the 250mA  rating and possibly damaging the 
cathode's emissive coating, I tuned up with 50wpm dits,  Power out was c. 
1kW PEP with 10w drive.  

cheers, Jeff 

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


--
FAQ on WWW:               http://www.contesting.com/FAQ/amps
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com