Date: Thu, 8 Sep 2016 21:44:18 +0000
From: Bill Turner <dezrat@outlook.com>
To: Amps group <amps@contesting.com>
Subject: Re: [Amps] What Do you think?
Something is wrong with the numbers. 3500 V at 500 mA is 1750 watts DC
input. If you were measuring 1500 watts RF output, that would be an
efficiency of about 86%, which is impossible with a class AB linear
and highly unlikely even if operated class C.
I would recheck the meter calibration before buying.
73, Bill W6WRT
## I agree, something is amiss...and it might be the B+ meter...and /or the
plate current meter. You could temp place a fluke DVM in series
with the existing analog 0-1 A meter to get an accurate p;ate current reading.
## Most of those 0-1 A dc ammeters are fairly accurate. The B+ meter
could easily be out to lunch... typ caused by using carbon comp resistors
in the series string for the B+ multiplier..for the B+ meter. They will typ
drift
30% on the high side. That means your B+ meter will be reading way down
on the low side of the actual B+ voltage.
## The other concern is the tubes, and availability. Half decent 4-1000s are
rare.
3-1000 Zs are very rare. If 4-1000s used, typ no load B+ is 4800-5500 vdc.
They require a lot more drive than a 3-1000Z. 3-1000Z sucks a lot more idle
current,
and requires more bias vdc.
## If it has 2 half decent tubes in it, plus some spares, you are probably
ok. Any Single
3-1000 Z or 4-1000 will do an easy 1800-2000 w pep out. Any 2 x holer, with
200 w
of drive should be aprx 4-5 kw out... provided the xfmr is big enough.
## the B+ meter would be easy to fix, if outa whack, just use the correct
resistors for the string.
Jim VE7RF
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