I have a background of 2 disciplines. One is professional electronic
products, design, support and making customers satisfied after the Sales
Department promised them bla bla bla about the product. The 2nd is of
course my hobby of ham radio.
I see and have been held to SPECIFICATIONS as a guaranteed performance
contract. Every model must meet these numbers under specific conditions.
Temperature, voltage, humidity, altitude, impedance, external RF/noise
influences and etc etc.
Then there's the "typical performance" set of numbers. These are not
guaranteed but simply state the most units meet these numbers most of the
time.
With regard to IMD performance, again from knowledge and experience, to
achieve optimum, one must have very carefully matched beta devices. Thus the
reason why some companies sell components in match pairs. While ideal, and
typically a bit costly, and I'd expect from a Tentec viewpoint the factor of
production output (yield) vs. scale of economics and a few other factors,
general devices will make the FCC guidelines all of the time. (Tentec may
wish to comment on this to the reflector or direct to me.)
Ideally, some standard production lot could be submitted for test, the
results obtained and then some percentage of the high and low numbers
discarded then publish the mean mathematical number as a specification. It
works, time consuming and expensive. The question to be answered, is it
worth it for a hobby?
73
Bob K4TAX
----- Original Message -----
From: <al_lorona@agilent.com>
To: <w9ac@arrl.net>; <tentec@contesting.com>
Sent: Tuesday, April 16, 2002 11:32 PM
Subject: RE: [TenTec] OMNI VI Transmit IMD
>
> Right, Paul. This is another way of approaching the question I posted last
> week (about which no one has really had anything to say). If the same
final
> amplifier design can vary by that much... it throws into doubt the whole
> concept of testing one unit and calling it representative of the whole
lot.
> Manufacturers need to be more clear about whether their specs are only
> typical numbers -- that your radio may or may not achieve-- or
guaranteed.
> I suspect that they are only typical values and can vary quite a bit due
to
> the manufacturing process.
>
> If that is true, then the measurements in QST's Product Review are much
less
> meaningful than we thought. There can be just too much variation between
> units to attach any statistical significance to pulling one unit off of
the
> production line and testing it and then declaring that all other units act
> like that one 'golden' unit. Note that this is not a statement about
ARRL's
> testing methods, but about the units they are testing.
>
> In the business world, customers can get pretty upset if their unit does
not
> meet a certain spec. But that's because it's understood that the spec
sheet
> holds guaranteed numbers. In other words, if your unit doesn't meet these
> specs, you get another one or get your money back. Correct me if I'm
wrong,
> but it's been my understanding that of Kenwood, Icom, Yaesu, and Ten Tec,
> only Ten Tec has this kind of policy. But I don't know if Ten Tec's specs
> are actually guaranteed.
>
> I am writing this at the risk of chasing away even more subscribers to
this
> list. Another one unsubscribed just today. At this rate, by mid-November
> there will be only two of us left.
>
> Al W6LX
>
> >
> >
> > > It's peculiar that what must be essentially the same final
> > comes in with
> > > much worse numbers when tested as the OMNI VI +.
> >
> > That is why I take the tested and published IMD figures with
> > a grain of salt ...
> > Performance as measured on one radio sample cannot be
> > extrapolated into the entire life cycle of the product.
> >
> > -Paul, W9AC
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