I doubt it's the tube, Alfredo. You didn't describe the circuitry, but it
sounds as though your 3CX800 amp is 20% more efficient than your 8877 amp!
I built an 8877 for 144 MHz that provided ~60% efficiency, that is 2500Wdc
input for 1500W RF output, using slightly higher Ep than you (4kV), but had
to experiment quite a lot to even allow this efficiency. For one, I had to
change chassis dimensions (!) because the first chassis used had some weird
resonance that would not allow the plate tank circuit to tune well; going to
a 2" wider chassis helped a lot. Isn't VHF fun?
WB2WIK/6
"Each success only buys an admission ticket to a more difficult problem." --
Henry Kissinger
> -----Original Message-----
> From: Alfredo Rosati I5UXJ [SMTP:alfredo@cln.it]
> Sent: Monday, November 19, 2001 3:26 PM
> To: amps@contesting.com
> Subject: [AMPS] 8877 efficiency
>
>
> i have an 8877 in 2 meter
> with 50 watt input
> 3700 volt 700 ma 50ma grid
> i have in output only 1250 watt.
> if the input is 100 watt i have 2000 watt but 1,1 Amp and grid 120ma.
>
> i have an 3cx800 that with 40watt input 3100 volt 650ma put 1400 watt
> output.
>
> is my 8877 defective????
> how much power in your 8877 amplifier in two meter you obtain ??
> hello i5uxj
>
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