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Old June 4th 09, 05:09 PM posted to rec.radio.amateur.antenna
Jim Lux Jim Lux is offline
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First recorded activity by RadioBanter: Mar 2007
Posts: 801
Default Using Tuner to Determine Line Input Impedance

dykesc wrote:
On Jun 3, 2:17 pm, dave wrote:

http://ytdp.ee.wits.ac.za/smithchart.pdf

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=8763


I don't run Linux Dave. Is there a Windows version? Meanwhile I am
going at it manually with a Smith Chart. At multiple frequencies this
will take some time.

Dykes AD5VS


you can do it with an Excel Spreadsheet..

You know that at "match" the impedance looking into the tuner from the
antenna is the conjugate of the impedance looking into the antenna from
the tuner.

If you assume your transmitter is 50+j0 ohms (not a good assumption..
but you could make it closer to being so by putting a 10dB pad between
Tx and tuner, for instance)

Then, you calculate what the impedance the tuner is using the L and C
values (I assume it's a series L and a shunt C) ... you'll either have:

TxR plus L, shunted by C
or TxRshunted by C, then series L

A spreadsheet like XLZIZL does it in a flash.