> True indeed, so far most of the measured testing done
> at the ARRL and their peers is focused on the RF
> signal handling traits of a radio, little or no
> testing is done with overall RX system distortion of
> complex (voice type) audio signals. Nor is there any
> meaningful measurements done to determine the overall
> contributed noise of the RX's RF/IF and AF stages. The
> tests they do are very valuable, but they only tell
> half the story of how a particular RX really performs.
> That unfortunately leaves some very measurable
> parameters up to subjective interpretation.
It's unfortunate that we have decided the lack of useful data somehow
means all data is useless, and that many have concluded measurements
are meaningless.
Part of this is because some parameters are not measured, another
part is because we often don't understand what the measurements
actually mean.
All of this can be corrected. The ARRL is *very* responsive to
reasonable suggestions for testing, as proven by changes they have
recently made in response to input from reflectors like this one.
For example...in the past the ARRL published only 20kHz and wider
blocking and IM3 tests for receivers. Those measurements are useless
for close-spaced performance of a receiver because they are outside
the bandwidth of most roofing filters, and the wide spacing test
hides IM and blocking problems that appear after the roofing filter.
After some conversations on the Topband reflector, the ARRL changed
to include 2kHz spacing tests. The closer spaced testing sorts out
second mixer and later stage problems in receivers, and makes a
surprising change in the pecking order of rigs.
As I understand, they are now going to include CW transmitter
bandwidth measurements.That's something else that was long overdue,
as anyone who works CW on crowded bands probably has noticed.
If anyone has any suggestion, maybe we can hash it all out and make a
reasonable suggestion to the ARRL to include a few more tests.
Perhaps an audio response test and detector IM test would also be
useful to those who are more "sound oriented" in preferences.
Perhaps someone would be willing to write an article describing how
to tie measurements into real-world operation. That would be
extremely useful to correcting the myth that measurements are
meaningless.
73, Tom W8JI
W8JI@contesting.com
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