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True Ladder Line and Wire Antennas




How Should I Implement My New True Ladder Line Antenna System?

 600 ohm ladder line is extremely low loss feed line which lends itself well to operating under high swr conditions.  By using a single wire dipole antenna for multiple bands, the swr on the feedline will be high.  With extremely low loss feed line such as True Ladder Line, these swr losses are negligible.  The net result is a highly efficient antenna system.  We need to think of our antenna as a system, not just an antenna.  So the question is:  how do I get as much RF power to the antenna as possible through my antenna system?  The answer is low loss feedline combined with a tuner that can resolve the impedances presented to it by the feed line over a wide range of frequencies (bands).Here are the choices we have:

A)  Ladder Line from antenna feedpoint to the Balanced ATU at the transmitter location.  

B)  Ladder Line from antenna feedpoint to the Balanced ATU at the base of the antenna support structure and fed with low loss coax into the shack.   The remotely located ATU may be remotely controlled via stepper motors and a StepperTune-BT       controller (see at Tab at top of page: "Balanced ATU High Efficiency System"       or

C)  Ladder Line from antenna feedpoint to the Unbalanced ATU (with a balun at output of ATU) at the transmitter location (in the shack).  Operating full legal limit and high duty cycle modes such as AM and Digital may cause balun over heating!

D)  Ladder Line from antenna feedpoint to a balun located outside the shack and fed with coax (short as possible and low loss) in to the unbalanced ATU in the shack.  Operating  full legal limit and high duty cycle modes such as AM and Digital may cause balun over heating!   

I offer free system modeling to determine the impedance presented to the ATU and system efficiency.  Due to the modeling complexity, I do not model the coax part of the system when the coax is in a high SWR location of the circuit (as in D above when the coax is more than a few feet long).  Under this circumstance, I suggest using the "taboo" length chart described below.          

 Each of these options may provide exceptional results.  However, if operating "Legal Limit" with a high duty cycle transmission like digital, the Balun may heat up as in options C and D.   

Because the ladder line transforms the antenna feed point impedance presented to the ATU (due to high swr on the line), the length variation will change the impedance significantly (see "Feedline Length Modeling" tab at top of store page) presented to the ATU.

Impedance transformation to the ATU can be readily modified by changing the ladder line length.  I have found that this method works very well for 80 meters up to 10 meters.  160 meters requires larger changes in ladder line length to afford the impedance change necessary.  Therefore, I prefer to keep my ladder line fairly short (45 to 55 feet) to present a reasonable impedance to the ATU for 160 meters.  The other bands fall into line reasonably well.  I also have discovered through many system models that the impedances presented to the ATU for 160M and 80M are much easier to resolve by the ATU if I can keep the antenna feedpoint at least 45 feet above ground.  

 I have optimized a antenna system for 160-80-40 meters which results in a system efficiency in the mid 90% range!   This system is comprised of a center fed dipole (feedpoint 55 feet above ground) of 215 feet and a TrueLadderLine length of 45 feet.  The Balanced ATU is located at the base of the tower (see below) and remotely controlled with a StepperTune-BT.  The antenna length of 215 feet results in a reasonably low SWR on all three bands simultaneously which affords efficiency numbers in the high 90% range!

I also prefer an Inverted V configuration which has a near Omdi-Directional pattern!  If your rea lestate can not accomodate a full 215 feet, folding the ends down toward the ground along a non-metallic support works well also.  With the ends folded downward, I try to keep them at least 10 feet above ground.

I look forward to having a QSO with you on the air!  Best 73's, Gary K7EMF

Preferred TrueLadderLine and ATU Installation:



 Modeling Your Antenna, TrueLadderLine & ATU Before Building The System

(Copy & paste:    into Google to see a larger display of the video or zoom in on the video below using ctl + rolling your zoom wheel on your mouse)