Posted by
Mike K8CN on
Apr 02, 2012; 5:58pm
URL: http://elecraft.85.s1.nabble.com/BL2-w-Multi-Band-Dipole-tp7429655p7430421.html
Hi David,
An 18 inch jumper cable won't produce a dramatic shift in feedpoint
impedance over that presented by a direct connection (via a double male BNC)
to the K1/K2 ATU even on 10 meters. If an adequate SWR can be obtained by
the ATU (VSWR less than 2.0) with the coax jumper in place on the bands of
interest (you may need to try the two different balun ratios), you can be
happy.
If you want to see the possible difference in the impedances presented to
the ATU for any given impedance at the BL-2 BNC connector, the TLW program,
written by Dean, N6BV and supplied with recent editions of the ARRL Antenna
Book, will calculate for you the transformed impedance at the end of an
arbitrary length of feedline. It's not necessary in your practical
situation, but it is interesting and educational if you've not worked much
with feedlines.
The only concern with the direct connection is the case when there may be
repetitive movement of the 450 ohm window/ladder line; you'll want to have
some separate strain relief to prevent repeated flexure of the BNC female
connector. The ATU connectors on my K2 are well-secured to the case, but
the connector bodies are plastic. For an indoor shack environment you
should have no problem either way.
73,
Mike, K8CN
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