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Re: Geosynchronous Satellites



on 12/24/00 8:50 AM, Phil Karn at karn@ka9q.net wrote:

> Are you really saying that it's impossible to make a FM HPA in the
> 10-100w range with greater than 7% efficiency? I think a lot of people
> would argue with you on that one.

No, Phil, not at all.  In fact, it's done all the time.

However, most base stations in the cellular industry now use multi-carrier
linear amplifiers even though they are amplifying FM signals.  They have to
be linear because you are amplifying more than one signal at a time and
intermods would result from a non-linear design.  Even your precious CDMA
needs highly linear amplifiers.

All this with FM signals!

Go and check the efficiencies of any of the linear amps sold by the
thousands by companies such as Powerwave or Spectrian.  I think that will
show I am correct.

With the exception of Ericsson, all of the major base station players pretty
much use some form of Feed Forward linear amps in the base stations.  From
the Lucent LAC to the Motorola ELPA, they are all very, very inefficient,
but very, very clean.  Before the days of high cellular traffic and before
the days of digital signals single channel FM PAs were very popular.  But no
more.

Jon

-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)

Member:  ARRL, AMSAT, DXCC, NRA

http://www.qsl.net/ke9na

"A life lived in fear is a life half lived."

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