[AMRadio] Amplifier to use with my DX-60


Bob Bruhns bbruhns at erols.com
Thu Mar 16 19:54:55 EST 2006


Yes, those numbers are possible in amateur service.
When I ran a pair of 3-400s linear, I ran about 800
watts carrier input, I got about 160 watts carrier
output, disspipation about 640 watts, 200 % mod, and
about 1500 PEP out.  (Efficiency gets bad when you set
them up that way.)

If I turned the audio down to about 100%, I could raise
the carrier level and get 350 watts carrier output,
carrier input about 1100 watts, PEP about 1500 watts,
dissipation about 750 watts.  The tubes did get hot
that way, though.

  Bacon, WA3WDR


----- Original Message ----- 
From: "Jim candela" <jcandela at prodigy.net>
To: "Discussion of AM Radio" <amradio at mailman.qth.net>
Sent: Thursday, March 16, 2006 7:22 PM
Subject: RE: [AMRadio] Amplifier to use with my DX-60


>
> 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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