Richard Clark wrote:
On Tue, 2 Sep 2003 00:28:12 +0100, "Ian White, G3SEK"
wrote:
AN1526, from which I'm quoting above, supersedes AN282. It was written
about 25 years later in an attempt to clear up that inherited mess of
loose definitions... but apparently with limited success.
Hi Ian,
25 years after the 60's, and yet AN282 is still published by Motorola
in 1991 by my copy. Further, it appears to survive through to 91
without any appearance of AN1526 which superseded it. This would
suggest that this application note, if published in the 90's
represents quite a bulk of material (nearly half again the total AN's
by number following 1991) published in 10 Years? 1968 + 25 = 1993
which suggests rather a revolution in thought over two years and
clearly not within the scope of credibility. These publishing date
games are too inspecific with your reference clearly in front of you.
Don't you know to surer accuracy?
I only know what Motorola say in HB215/D, 'RF Application Reports'. As
you know, Motorola don't go back and re-write old application notes -
they only publish newer ones, leaving users to sort out which aspects
have been superseded and which are still valid.
AN282 is still included in HB215/D and older compilations because it
contains valuable information on other topics.
The application notes themselves are not dated. The list of references
in AN1526 states that AN282(A?) was published in 1968. The publication
date for AN1526 can be bracketed to the early 1990s (after the latest
dated reference that it quotes, and before 1995 when it was re-published
in HB215/D).
That is sufficient to establish my point: that the thinking in AN1526 is
based on about 25 years further experience after AN282.
I still see nothing of substance, merely suggestion:
That is certainly a statement requiring some careful
thought, especially since the term 'output impedance' is somewhat
misleading [so even Motorola admit that]. ... as described in [AN282]
it is the conjugate of the LOAD impedance at the fundamental operating
frequency which allowed the transistor to 'function properly' [when the
load impedance was varied in a test jig]."
Does not say what it is, but what it was by testing - hardly
revolutionary nor upsetting.
Certainly you could come up with a smoking gun couldn't you?
If you can't get it from the key paragraph I quoted, then read all 15
pages of AN1526. If you still can't see that your notion about "device
output impedance" is shot clear through, then neither Motorola and I can
help.
Complete
with an actual, demonstrable specification for the item I offered
(seeing as you still lack any concrete example). What does your new
and updated resource say about the MRF 421.
You know perfectly well that AN1526 won't say anything about your
specific pet device, so what was the point of asking that question?
Does it abandon that
discussion entirely to this new-age era of all being unknowable?
And that is an even worse travesty of what Motorola and I are saying.
If you want to measure the *true* output impedance of an MRF 421 - as
distinct from the load impedance given in the data sheet - then go ahead
and do it. After all, you're the one who claims it is an important
design parameter.
I'm the one who says it is (a) not what you think it is; and (b) not
important anyway.
Now it's up to other people to judge the technical truth of the matter.
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek