Don Wilhelm wrote:
If your tuner has a limited range and cannot properly match the
feedpoint impedance of the feedline, adding (or subtracting) a length of
line to the feeder length can bring it into a range that your tuner can
match. I would suggest adding or subtracting in 1/8th wavelength
increments until you get it close to the desired range and then go to
1/16th wavelength additions or subtractions. The feedline acts like an
impedance transformer when it is operated with an SWR other than 1.
Or, use N6BV's TLW [comes with the ARRL Antenna Book 20th ed] and just
calculate it. I modeled one of my low band antennas to get the feed
point impedance, and then used TLW to compute the open wire line length
to the balun. Worked great.
73,
Fred K6DGW
- Northern California Contest Club
- CU in the 2008 Cal QSO Party 4-5 Oct 08
- www.cqp.org
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