Bob is right on the money...
I and others tend to agree that following a circulator
or isolator in a typical repeater duplexer layout does
not require an additional low pass filter.
As an example:
The previous mention of the MA associates Isolator,
which was used in their antenna combiner systems...
was not followed by a low pass filter.
Some people use them, some don't and see no
requirement to do said. In some cases it's a good
idea but not a must have.
cheers,
skipp
> Bob Dengler <[EMAIL PROTECTED]> wrote:
> At 5/7/2005 10:53 AM, you wrote:
> >Steve,
> >
> > There is nothing special about the low-pass filter
> > that might require you to use a particular brand
> > name. A ferrite isolator is a nonlinear device, and
> > therefore it will generate a strong second harmonic
> > which must be attenuated by either a notch filter
> > or a low-pass filter.
>
> Not always. If the isolator is driven far below it's
> rating, it may not go nonlinear. We once tested an
> EMR Corp. 220 MHz isolator being driven with ~90
> watts. The output spectrum from our RFPA was no
> different with the isolator in line (no increase
> or decrease in harmonic content).
>
> If you have a power attenuator handy, it might be
> worth actually looking at the harmonic levels
> coming out of your isolator with a spectrum
> analyzer. You can't use a coupler for this test
> because it's frequency response will taint the
> measurement.
> Bob NO6B
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