Date: Tue, 16 May 2017 21:33:14 -0600
From: Larry Benko <xxw0qe@comcast.net>
To: amps@contesting.com
Subject: Re: [Amps] Tuned Input
<The calculator below gives incorrect results:
https://wetnet.net/rf_design/pinet.cgi
For example Zsource = 50+j0, Zload=30+j0, Q=2.5, Freq = 14MHz produces
C(source side) = 413pF, L = .716uH, & C(load side) = 320pF which does
NOT match
The calculator at https://www.eeweb.com/toolbox/pi-match produces for
the same data as above
C(source side) = 568pF, L = .340uH, & C(load side) = 694pF which does
match & has a Q of 2.5.
73,
Larry, W0QE
## http://n9zia.ampr.org/pinet.cgi This one does work, and produces
identical
results to what larry depicts above.
## https://wetnet.net/rf_design/pinet.cgi This is the one that w7ry
noted...and is incorrect,
not only are the results outa wack, they have the source and load reversed ! I
entered 1960 ohms
for the tube Z and 50 ohms for the load, and 1.8 mhz and a Q of 10, and C1 + C2
are reversed...
plus its wrong anyway. Funny thing is,I found the correct one by backing up,
and clicking on the...
... green bay professional packet service link at the top of the incorrect
formulae page..... then
scrolled through their index to find the PI formulae. Which happens to then
be the correct
one...and in the same format too.
## another place to go is the GM3SEK website and use his PI spread sheet.
Its more for
tube amps, and will not handle 2 identical impedances, they have to be at least
1 ohm apart.
No big issue, its still works by using say 50 to 49 ohms or 49 to 50 ohms.
## You also have to note to factor in the Tube C..and remove that from any C2
value that the
correct formulae spits out.
Jim VE7RF
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