On Wed, 28 Apr 1999 21:36:17 -0500 Jon Ogden <jono@enteract.com> writes:
>
> >> Bricks are notorious for their non-linearity and no
> >> matter how good yours may be, I doubt that it is as linear as
> your
> >> exciter.
> >
> >Explain that please? The output devices usually come from the same
> >company, Motorola, and except for the power gain are darn near
> identical.
> >Dont blame the device if its due to poor execution.
>
> Well, any amplifier except a PERFECTLY linear amplifier (which
> doesn't
> exist) will produce harmonics and intermod. A class B device will
> produce more than a class AB device which will produce more than a
> class
> A device. I think most "bricks" are either class AB or B. They are
>
> therefore NON-LINEAR devices. Any non-linear device will produce
> harmonics. Now, do the amps have low pass filters on their output
> to
> knock these down to FCC specs? Perhaps. But IMHO, even with a
> perfectly
> clean signal on the input of an amp, the output will have some
> spurious
> by-products.
Show me a rig with a perfectly clean output. What you buy is what passes
the current FCC regs, etc. And a lot of older rigs wont even pass that.
Therefore the old GIGO theorem would seem to say an additional filter on
the input to an amp is the best way to go.
Then the filter on the output of the amp is there strictly to clean up
the amp. Look inside the common VHF bricks and you will see very minimal
filtering, usually just a 1/4 wave stub on the output.
For superb rejection get a DCI bandpass unit; they do a great job on the
RX also in RF noisy areas.
Perhaps they aren't enough to worry about. I.C.E.
> claims
> they have never been able to measure them. I don't know. I don't
> have
> the equipment to test it out.
>
> 73,
>
> Jon
> KE9NA
>
>
> -------------------------------------
> The Second Amendment is NOT about duck hunting!
>
> Jon Ogden
> KE9NA
>
> http://www.qsl.net/ke9na
>
> "A life lived in fear is a life half lived."
>
>
> --
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>
>
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