Wednesday, May 4, 2016

Simple Ham Radio Antennas--How to Build a ZS6BKW Antenna. Post #765.

How to Build a ZS6BKW Antenna (optimized G5RV)
(https://www.vk4mdx.wordpress.com/2013/09/02/how=to-build-a-zs6bkw-antenna-optimized-g5rv-antenna/).
Accessed on 05 May 2016, 02:21 hrs, UTC.
Author:  David Olsen (VK4MDX).

The original G5RV antenna designed by Louis Varney (G5RV) (SK) continues to serve radio amateurs well around the world.  Although Varney clearly designed this dipole as a 3/2 wavelength antenna for 20 meters, it can be used on amateur radio bands from 80 meters through 10 meters with a suitable tuner. Performance on bands other than 20 meters can be variable because of many factors, including feedline length, the type of feedline, and very high SWRs on some bands.  As a 20 meter antenna, the G5RV does an excellent job.  On other amateur radio bands, performance often suffers.

However, with a few modifications regarding antenna element length and the correct combination of 50 ohm coaxial cable and 450 ohm ladder line, it's possible to improve the all-band performance of Louis Varney's original idea without encountering destructive SWRs or marginal signals.

In this post, David Olsen (VK4MDX) uses a design from ZS6BKW, which he calls an "optimized G5RV".  The performance of this antenna on bands ranging from 80 meters to 10 meters is quite good, with 15 meters being the only band not within the performance parameters of the ZS6BKW design.  In David's approach, 450 ohm ladder line is used as a 1:1 transformer into a length of 50 ohm coaxial cable, which runs into your transceiver.  The dipole is an electrical 1.35 wavelength (see illustrations).  In order to get critical measurements right, David recommends the use of an antenna analyzer.  Some cut and trim will be required to get this antenna to work properly.

Some of the comments attached to David's article offer helpful guidance in case you experience difficulties building this antenna.

If you follow David's instructions closely, you'll have a much improved version of Louis Varney's original G5RV antenna without the need for an antenna tuner.
This antenna would make a great weekend project.

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Thanks for joining us today!  Aloha es 73 de Russ (KH6JRM).