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Re: [Amps] Amp output power

Subject: Re: [Amps] Amp output power
From: Steve Thompson <>
Date: Mon, 24 Aug 2015 22:31:06 +0100
List-post: <">>
If you check at

there's several data sheets. I came across a copy of the one with 1370W output spec. and copied it to David to host. I believe there was a spell where FCC applied rules relating to output power spec. of the devices in a transmitter, hence the 750W rating appearing so a pair was valid for a 1500W amplifier.

I think the same applied in the case of Svetlana 4CX800A data.


------------ ORIGINAL MESSAGE ------------(may be snipped)

On Sun, 23 Aug 2015 18:25:38 -0700, Jim wrote:

The non-pulse rated 3cx800 max ratings are 2250V plate voltage, 0.6
plate amps. Typical operation at 2200V and 0.5A with 23W of drive will
get you 750W AB2 output.


That's interesting. At 2250 VDC and .6 amps, the DC input is only 1350
watts. At 60% efficiency, the RF output would be 810 watts and the
plate dissipation would be 540 watts.

The tube's rated plate dissipation is 800 watts, yet in class AB with
max Vp and Ip, you come nowhere near that rating. Most tubes will put
out RF well in excess of their dissipation rating. For example, a
3-500Z with only 500 watts plate dissipation will put out 750 watts
and still be within ratings.

The question is, why would a tube have such a high dissipation rating
if it is not capable of reaching that in normal class AB operation?
Perhaps it is intended for use in class A?

Seems strange to me. Your thoughts?

73, Bill W6WRT

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