Rich Measures wrote:
>>[G3SEK wrote:]
>>........
>>>Rp is 49.26 ohms. The 100 ohm suppressor R is in parallel with the
>>>95.6nH suppressor inductor, which Wes calls Ls. 93.46 ohms is not the
>>>resistance of the suppressor R.
>>
>>On that subject I think we're all out of step except you, Rich.
>>
>Were Wes' measurements made with 200nH (roughly 10-inches of wire)
>inserted between the device under test and the test instrument?
I don't understand the relevance of that question; but the answer of
course is "No".
Let's try again with the line from Wes's tables that we were already
discussing. Here is the whole line, copied-and-pasted from Wes's
measurements for a pure NiCr inductor, with NO external shunt
resistance:
FREQ (MHz) Ls (nH) Q ESR Lp (nH) G (mS) Rp (ohm)
10 95.3 15.5 N/R 95.6 10.70 93.46
Wes's own commentary:
"Column 1 is the test frequency in MHz.
Column 2 is the measured effective (series) inductance...
Column 3 is the measured Q.
Column 4 is the measured equivalent series resistance.
Column 5 is the measured effective (parallel) inductance.
Column 6 is the measured shunt conductance in milli-siemens.
Column 7 is the computed parallel resistance."
Let's look at those in more detail.
Column 2 is a measurement of what's normally identified as Ls. (Wes
added some minor details about distributed capacitance, which aren't
relevant here.)
Column 3 is the measured Q.
Column 4 would have been the equivalant series resistance, which is the
exactly same thing as Rs, but unfortunately Wes didn't record that
measurement. Never mind; we can calculate it.
Q = (XLs/Rs) so
Rs = 2*pi*f*Ls/Q = 0.386 ohms.
Column 5 is Lp, the measured equivalent parallel inductance.
Column 6 is the measured shunt conductance, which by definition is
(1/Rp), so Rp = 93.46 ohms
Column 7 did exactly that calculation for us.
Sanity checks:
1. Calculate Q from the values provided for Lp and Rp.
Q = XLp / Rp = (2*pi*f*Lp)/Rp = 15.56
This agrees with the measured Q in column 2 (differences are due to
rounding errors in the numbers given).
2. From the measured Lp and "nearly-measured" Rp, calculate Ls. It would
also have been nice to check agaisnt a measurement of Rs, but
unfortunately Column 4 (ESR = Rs) is empty.
>From the parallel->series formulae - which I'm not going to type out a
third time - it works out that Ls = 95.21nH. This agrees with the
measured Rs (once again, within minor rounding errors).
All Wes's reported measurements hang together perfectly. There aren't
any mysteries, and there is no reason to deviate from the standard
textbook meanings of Ls, Rs, Lp and Rp.
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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