>
>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.
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