[AMRadio] Amplifier to use with my DX-60


Jim candela jcandela at prodigy.net
Thu Mar 16 19:22:32 EST 2006


Don,

   You said: "So you could run maximum 1500 watts DC input to those tubes,
with 500 watts
carrier output, and 1000 watts dissipated by the tubes".

Reply from Jim WD5JKO:

   What is stated above is correct if the tubes can dissipate 1000 watts of
heat (like two 3-500Z's flat out blushing), and the drive is adjusted to
about 1/4th that for maximum PEP output. In this case the efficiency is
assummed to be about 33%, so 1500 X .333 = 500 watts. The efficiency may
vary some, and is usually lower then that, so the 33% assumption is only a
first guess. It could be 25%, and that really upsets the situation making
the linear more of a heater, and less of a transmitter.

   One good thing about the 1500 watt PEP output power rule we all complain
about is that efficiency doesn't matter as much now. You can legally run a
15 KW PEP input amplifier with 10% efficiency to provide 1500 watts PEP
output. It wouldn't make a lot of sense, or be practical, but it's now
legal. Back in the 1000 watts DC input days things were a lot different, and
the SB-220's input would likely exceed 1000 watts DC before the AM carrier
got to 375 like we often do today with these amps. The point here is that
for low efficiency linears, or grid modulated amplifiers,  we can sometimes
run more power today on AM then before the rules changed from 1000 watts DC
input to 1500 watts PEP output. Of course this isn't the case with plate
modulation where an output PEP at or maybe more than 3KW PEP WAS possible,
and completely legal.

Regards,
Jim
WD5JKO


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net]On Behalf Of kenw2dtc
Sent: Thursday, March 16, 2006 4:21 PM
To: Discussion of AM Radio
Subject: Re: [AMRadio] Amplifier to use with my DX-60


Don says:

"So you could run maximum 1500 watts DC input to those tubes, with 500 watts
carrier output, and 1000 watts dissipated by the tubes"

*******I need a little help with the math here Don.  You are suggesting that
with a class B linear in AM mode, one can get 2000 watts PEP with 1500 watts
input ?

73,
Ken W2DTC

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