But Maury, tubes are much prettier, especially in a dark room. No
comparison. -WB2WIK/6
"If everything seems under control, you're just not going fast enough." -
Mario Andretti
> -----Original Message-----
> From: Maurizio Panicara [SMTP:i4jmy@iol.it]
> Sent: Wednesday, September 18, 2002 11:21 AM
> To: 2; Kim Elmore; AMPS
> Subject: Re: [Amps] A general question about why anodes get hot
>
> >
> > Tube-type amplifiers dissipate roughly half as much heat as the amount
> of
> > RF they produce.
>
> In my experience with broadcast FM transmitters, solid state mosfet
> amplifier are not so much better than a tube PA plate efficiency already
> when the device is alone, I mean a single pushpull unit.
> Actually a 300W mosfet module is better in terms of efficiency if compared
> with the equivalent level vacuum, but as the power is increased the story
> becomes different with solid state.
> A number of modules and coulpers (typically wilkinsons if one doesn't want
> to see often all the mosfets dead in case of failure) are required to
> obtain
> large power and, as well extra modules are added some extra loss arise and
> in spite of (claimed) "super efficient" switching PS and super efficient
> PA.
> The claimed broadband units (untuned) are a compromise and the solid state
> PA effiiciency may vary (decrease) noticeably varying the frequency.
> When lab measures are taken seriously, beyond a certain power the real
> overall efficiency of a solid state PA is not different than a tube
> amplifier.
> Not rarely I mesured is worst.
>
> 73,
> Mauri I4JMY
>
> > - R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
> > www.vcnet.com/measures.
> > end
> >
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