Richard Clark wrote:
On Fri, 5 Sep 2003 12:02:02 -0500 (CDT),
(Richard Harrison) wrote:
Richard Clark wrote:
"Motorola (in their confusion) offers:
For example, in the 180 Watt version the input transformer is of 16:1
impedance ratio, making the secondatry impedance 3.13 Ohm with a 50 Ohm
interface."
Does not seem confused to me.
16 x 3.13-ohm= 50 ohms by my calculation.
Hi Richard,
The expression of "confusion" is not original, nor embraced by myself.
It represents my wry comment, an irony in that this term (confusion)
applied to Motorola's specifications is rejected by data, experience,
Motorola (except through a particular reading of one application note
that seems to bear no relation to any known experience), and at least
three more vendors that I have supplied who all conform to this
practice.
Technical literature for RF Design Engineers is chock full of this
consideration that is taken for granted in academic texts (it would
only muddy the waters for students, I suppose). However, when
unmentioned, except in the footnotes, endnotes, or appendix (all
unread at hazard to speed readers) this academic shortfall gives the
impression that the topic is of no interest. Hence we read of
Motorola being confused about their specification of source Z that
everywhere in their literature is expressed with deliberation and
planning. To date, and through more than several inquiries to expand
upon this "confusion" I have been offered no data, other form of
specification, how it bears on application, or any correlation to
personal experience.
If you follow the thread back up several, you will find Tam struggling
to find negative confirmations, and through his lack of close reading
his "condemnatory" sources in fact supply me with all the engineering
details I had described as being part and parcel to a common RF
Finals' Deck.
Tam is innocent!
I take full responsibility for planting the word "confusion" in
Richard's mind. What he's done with it is something else again...
As the records of this newsgroup show, the context in which I used the
word (actually, the word was "confused") was:
QUOTE *************************************
Some manufacturers state the conjugate, others don't. Even Motorola have
changed their terminology over the years: sometimes it's "output
impedance" or "Zout", sometimes it's "Z(subscript OL)", sometimes it's
"Z(superscript *)(subscript OL)".
Motorola's AN1526 was written in the 1990s to clear up this mess.
[...]
AN282, from which you quote, was first published in 1968. The truth
about load impedance is in there to be seen, but I'd be the first to
agree that it's not stated clearly. Motorola then confused the issue by
continuing to talk ambiguously about "output impedance" for at least
another 20 years.
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.
END QUOTE *************************************
I stand by those statements and take full responsibility for them.
Motorola's ambiguous use of "output impedance" - and three different
symbols, over the years - when all the time they meant "load"
impedance", has indeed been confusing.
The way Richard has subsequently misused the word is purely his
responsibility.
If he twists the facts again, to mislead others about what was actually
said (as he has just attempted to mislead Richard H, carelessly accusing
Tam in the process) then I will simply post the above quotation again.
The beauty of newsgroups is that everything that anyone has ever posted
is on the record, for any reader to judge.
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek