Rich Measures wrote:
>>Rich Measures wrote:
>>>>>Sample problem: Part I: Ls = 200nH, Rs = 200 ohms, f = 100MHz. What
>>>>>is the Admittance, Y, Mr. White? A running description of your solution
>>>>>would be helpful.
>>>>
>>>>No, I won't bite. There is absolutely no need to drag admittance into
>>>>this discussion.
>
>When L is in parallel with R, admittance Is the name of the game. When L
>is in series with R, impedance Is the name of the game.
Not correct: when L and/or C and/or R are connected in parallel, there
is NO automatic change into susceptance and conductance. These
admittance parameters are only an alternative, optional route through
the math. You can choose to stay in normal units of resistance and
reactance, all the way.
>
>>>Then on to Part II: what is the parallel-equivalent resistance of 200nH
>>>in parallel with 200 ohms at 100MHz? (presumably using the method
>>>described below)
>>>
>>200 ohms, at ANY frequency, by definition - no calculation is required.
>>
>.....not the definition of Rp in Wes' measurements.
Or rather... not in your interpretation of "Rp" in Wes's measurements.
Wes - the guy who made the measurements - emphatically disagreed with
your interpretation, and he made the measurements.
>
>>Part III - it's my turn: what is the series-equivalent form, ie what are
>>Rs and Xs at 100MHz?
>>
>>XL = 2*pi*100E6*200E-9 = 125.66 ohms
>>
>>XL is equal to Xp by definition, because L and R are connected in
>>parallel.
>>
>However, when an L, or a C, and an R are connected in parallel, we have
>susceptance and conductance in Siemens instead of reactance (X) and
>resistance in Ohms, which, at a discrete frequency result in an
>admittance (Y) instead of an impedance (Z).
As I said above, that's not correct. Admittance, susceptance and
conductance are merely an alternative route through the math. You can
choose to stay entirely in resistance and reactance, as shown in my
earlier posting which is completely standard network theory.
>
>However Y can be converted to Z, and vice-versa.
...and when you do, you reach exactly the same impedance (R and X)
results as I gave, only more slowly because of having taken an
unnecessary detour into admittance.
>
>
>>R = 200 ohms = Rp by definition as we hopefully agreed above.
>>
>We do not because we are discussing Wes' measurements, not the *ARRL
>Handbook* (which used to be called the *Radio Amateur's Handbook*).
>
If you don't agree that the parallel-equivalent resistance in a
parallel-connected circuit is - by definition - just R itself, you're
marching out of step with every definition "Rp" I've ever seen.
>>What do you make Xs, Rs and Q, Rich?
>>
>Q is not 1.59. "Xs & Rs" look ok, however, Wes and I use "Rp" where you
>use "Rs" to designate the parallel-equivalent R.
That's incorrect on three counts.
1. This "Wes and I" line won't stand up to examination. The record shows
that Wes emphatically disagreed with Rich's interpretation of his
measurements, so much so that he actually asked Rich to remove all
reference to those measurements from his web pages; Rich refused. Wes's
own web pages (referenced by Gerard a few days ago) tell the full story.
2. My terminology and analysis agree exactly with Wes's. It was I who
originated the log-log plot of suppressor Q versus frequency, and sent
it to Wes. He agreed with my calculations and published it on his own
web pages.
3. I'm the guy who keeps saying that the "s" in Rs stands for series-
equivalent; and the "p" in Rp stands for parallel-equivalent. Please
read my earlier postings correctly, and don't stand them on their head.
Multiple series<->parallel transformations are an area where it's very
easy to accidentally turn equations and/or terminology upside-down and
come to exactly the wrong conclusions. I firmly believe that is what
Rich is doing.
I'm happy to leave Rich and Carl to discuss the hands-on aspects of
suppressors, but I do feel it necessary to defend the good name of
network theory when it's being misused.
It's nearly 0130 here. Goodnight, America.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.demon.co.uk/g3sek
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