--- "Dr. Gerald N. Johnson, electrical engineer"
<geraldj@isunet.net> wrote:
<snip>
> I look at the
> transmitted phase noise plots and presume they are
> the same for the
> receiver oscillators.
>
I have never been convinced that looking at transmit
phase noise plots of a transceiver is a particular
valid test to measure its RX phase noise. It's not
prudent to assume that the RX phase will always be the
same as the TX phase noise. While the tests that the
ARRL does are useful, they far from complete or
exhaustive, I surely don't take them as gospel. For
example a highly interesting test to see would be to
test for overall internal noise generated in an RX by
measuring audio output power out with no signal and a
50 ohm termination on the antenna input. Further test
overall gain vs. overall noise produced at the speaker
for several different intermediate level signals, do
not just test for MDS or maximum signal that the RX
will take before crumpling. How about measuring filter
passband flatness? Or how about filter group delay?
Some additional testing of these kinds of parameters
may shed some light on the seemingly subjective views
of certain radios being better (or worse) than their
ARRL test results would suggest. Perhaps it is the
test methodology/criteria that is flawed, or at a
minimum incomplete?
One of my other major reservations of the ARRL tests
is that they typically use a single test specimen,
running tests on 5 or so units will provide a better
overall picture of a particular models traits.
> Some of the European ham magazine receiver
> checks do that
> blocking or IMD test continuously over a range of
> +/- 50 KHz.
This is a good idea, picking somewhat arbitrary spot
frequencies of say 2, 5, 20, etc KHz doesn't tell the
whole story. A continuous range +/- 50 KHz, or even
more, will give a better overall picture.
> In most
> cases a combination of reciprocal mixing and second
> mixer overload are
> very pronounced at the smaller frequency
> separations.
But yet it is the close in <2 KHz range that probably
matters as much or more than the wider separations.
Duane
N9DG>
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