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Author Topic: 3-1000z vs pair of 3-500Z  (Read 4348 times)
WA2MGB
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« on: August 16, 2004, 03:35:34 PM »


I have been told that a pair of 3-500z tubes are the same in all ways (regarding output) as one 3-1000z.

Question:  Why then when I run AM on 75m do my 3-500's run pumpkin orange and my 3-1000z barely seems to break a sweat with little color change?  And yet the output is the same <set for legal limit carrier AM>

Are the 3-500z's working "harder"?

Ted
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WB2WIK
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« Reply #1 on: August 16, 2004, 04:52:57 PM »

Besides the differences in materials used and  thermodynamics of the tubes, you're undoubtedly comparing two different amplifiers.  Sounds like the one with the 3-1000Z in it is more efficient when run at this power level (I assume ~375W carrier power).

Multiply plate volts x plate amps, and then subtract 375W from that and see (for each amplifier).  My bet is the 3-1000Z is actually dissipating less power.

Not that it's a bad thing for the tube anodes to glow orange, that's a pretty normal color for these tubes.

WB2WIK/6
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WA2MGB
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« Reply #2 on: August 16, 2004, 05:10:33 PM »


Thanks steve,,,,I runn the BTI and a homebrew 3-500z side by side....Despite the fact the homebrew is much newer.   The BTI still a great performer.

Ted
WA2MGB
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W8JI
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« Reply #3 on: August 17, 2004, 07:56:12 PM »

The 3-1000Z normally shows a little less color than a pair of 3-500Z's do when dissipating the same power.

That's because the 3-1000Z has a bit larger anode area than the sum of anode areas in a pair of 3-500Z's.

In each case, you always want the anode to show some color while operating. Otherwise the tube will go bad.

In any case if you are running linear AM, efficiency should be 25% or so in both or less. If efficiency is much higher, you can bet you have peak clipping on 100% positive peaks.

73 Tom
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