> -----Original Message-----
> From: measures [mailto:2@vc.net]
> Sent: Friday, October 13, 2000 9:42 PM
>
> >Input bandwidth can be fixed by using a double pi, l-pi-l or other
> >more advanced network.
> >
> I have never heard of such being used in any amplifier.
Just because you haven't heard of it doesn't make it invalid.
Although it is not used in amateur amplifiers since the single pi
was "good enough" for tube exciters, more complex networks are
often used in commercial (broadcast, maritime, etc.) transmitters.
They provide better broadband performance and lower out of band
products.
There was an article in Ham Radio (late 70's or early 80's)
which discussed the use of a five section low pass filter to
cover 80 through 10 meters in lieu of five band switched single
band pi networks. The "component cost" was actually lower
(fewer capacitors and one fewer wafers on the band switch).
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