>Rich Measures wrote:
>
>>G3SEK wrote:
>>>Pulling some example figures out of the air, consider a suppressor that
>>>consists of 100 ohm resistor paralleled by 100nH. In series with that is
>>>say 200nH of connecting lead inductance between the tube and the pi-
>>>tank. At 100MHz, this network transforms into 1058 ohms in parallel with
>>>279nH.
>>>
>>Out of the air, indeed. . How about going through the calculations, Mr
>>White?
>>
>
>Out of the air, like hell!
>
the calculations will tell .
>You are in the business of selling and advising your customers on RF
>networks, Rich. Why should I have to spoon-feed you with basic network
>theory that you should already have digested?
>
Alas, the business has made no money for Rich. However, Rich paid his
help.
>But here we go again...
>
>0. This is a demonstration of an impedance transformation effect, so
>we're going to assume ideal component behavior.
>
but of course
>1. 100nH at 100MHz is +j63.83;
I got 62.83
>200nH at 100MHz is +j125.66
>
ok
>2. Now transform 100 ohms paralleled by +j63.82 transforms into its
>series-equivalent. The equations (as posted last weekend) are:
>
>Rs = Rp*Xp^2 / (Rp^2 + Xp^2) Xs = Rp^2*Xp / (Rp^2 + Xp^2)
>
>Answer: 28.30 in series with +j48.05
>
I got 28.32 ohm R, however I came up with +j45.06 ohms of X {cos 57.85
deg. x 53.22 ohms of Z}
>3. Add the +j125.66 in series, to get 28.30 +j170.71 (still series-
>connected)
>
hello
>4. This is now NEW NETWORK that includes the external 200nH. Transform
>this new network back into its parallel-equivalent:
>
It is my opinion that this is not a legal move. In other words, adding
external X to a parallel L-R circuit does not change the Admittance (Y)
of the parallel circuit. In other words, it appears that you are
trying to add oranges and apples, Mr. White.
Your calculation of how the 100ohm suppressor R became 49 ohms at 10MHz
in Wes' measurements would interest me.
---------------------
>Rp = (Rs^2 + Xs^2)/Rs Xp = (Rs^2 + Xs^2)/Xs
>
>Answer: 1.058K in parallel with +j175.40
>
>5. At 100MHz this is 1.058K in parallel with 279.17nH - voila!
>
>This impedance transformation is no less true than the impedance
>transformation that happens in your pi-network. That can be handled
>using exactly the same tools.
>
>Real-life networks are more complicated but those same tools will still
>handle them, if you include all the stray reactances and losses. It only
>gets more complicated, not any different.
>
>
>73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
> 'In Practice' columnist for RadCom (RSGB)
> http://www.ifwtech.demon.co.uk/g3sek
>
>--
>FAQ on WWW: http://www.contesting.com/ampfaq.html
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>Problems: owner-amps@contesting.com
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Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
--
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