Sunday, July 7, 2019

Ladder Line and SWR. Post 1921.


If you can't see the video, please insert this title URL into your browser search box: https://www.youtube.com/watch?v=1KUJPcRIUDE.

In our previous post, Stan Gibilisco (W1GV) explained the pros and cons of a coax-fed multiband HF dipole antenna.  Even with an antenna transmatch (i.e. "tuner") in line, high antenna SWR for all bands, except the one cut specifically for the design frequency, will lead to poor efficiency and power loss.

According to Stan, one way to keep feed line losses to a minimum would be to use a balanced feeder (ladder line, TV window line, or homebrew 600 ohm balanced line) with your HF dipole antenna.  Design your dipole for the lowest frequency of use, use balanced line to feed the antenna, and use a balanced antenna "tuner" to keep line losses and SWR low.

In this video, Stan explains the theory, operation, and use of ladder line, as well as where and when to use it.  If you can have only one HF antenna, feed it with balanced transmission line connected to a balanced "tuner" and get multiband HF performance.  If you don't have a balanced tuner, run the ladder line into a 4:1 or 9:1 current balun, and attach this combination to your regular antenna tuner.

My main HF antenna (80 meter inverted V) follows the example outlined by Stan in this video.  I have full HF coverage on 80/40/20/15/and 10 meters.  The feed line is connected to a 4:1 W9INN current balun, which in turn is attached to my old Drake MN-4 Antenna Tuner with a short length of RG-8X coax.  My old Swan 100MX is happy with the arrangement.

Stan's basic design is simple, inexpensive, and nearly foolproof.

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Thanks for joining us today.

Aloha es 73 de Russ (KH6JRM).

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Aloha es 73 de Russ (KH6JRM).