You know, Duane brings up something I have always wondered about.
An example: When a manufacturer says that their radio has 100 dB of dynamic
range, is that a guaranteed figure?
Or is it an average number? Maybe a typical number?
If it's guaranteed, I could conceivably measure the dynamic range myself,
and if it doesn't meet the spec, I could return the radio for my money back.
But I doubt if you could. I have not heard of a policy where you could
return a radio simply because it didn't meet some spec. That leads me to
believe that the numbers you see on a spec sheet or color brochure are
either typical or average values. If they are typical or average values,
there is a Gaussian distribution of that spec in a group of many radios of
that model. So the next logical question is, what is the sigma or width of
the Gaussian curve? If sigma is large, meaning the variation around the mean
is large, then you could get lucky and get a radio with much better than 100
dB of dynamic range, or get stuck with one with significantly less than 100
dB. So the one unit that ARRL tested... was it an average unit, a golden
unit, or a dog?
Once the product review is published, it becomes ham gospel. For ever and
ever, hams will point to the review and say, "See, that radio is junk," or,
"Hey, pretty darn good radio!", and the differences could largely be due to
nothing more than the statistical variation between units.
>
>
> 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.
>
> Duane
> N9DG>
>
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