Antennas By N6LF

Multi-turn loop receiving antennas for LFMF

For the next edition of the ARRL Antenna Book (the 25th) I've written a section on Multi-Turn Loop Antennas for LFMF reception.  It will be many months before this published and available from the ARRL.  I felt the topic might be of more immediate interest to the LFMF gang and have permission to post a copy of the draft: Download Chap 22 LFMF RX loops .

The ARRL note mentions direct experimental measurements of self resonant frequency.  Here is a note with more detail on the measurements and modeling comparisons between different versions of NEC:  Download Loop excerpt 2

LFMF notes

Here are some notes on LFMF tuning inductors which may be of interest:

Download Optimum Inductor l-D ratios

Download Optimum Q LFMF loading inductors

Download Wet Inductor Tests

630/2200m TX antenna

Download 630-2200m N6LF TX antenna

I've rebuilt my 630m TX antenna and retuned it to 2200m.  630m tuning will be added in due course.  Here is a description of the latest LF/MF TX antenna at N6LF

New 630 transmitting antenna a WD2XSH/20

I have recently rebuilt my 630m antenna to use a counterpoise in place of the radial system of 128 wires lying on the ground.  I wanted to see if a much simple counterpoise system would provide comparable efficiency.  Take a look at: Download N6LF Transmit Antenna July 2017

LF-MF antenna notes

 

The present draft of these notes, while far from perfect, may be helpful to many amateurs.  For that reason I've posted them in their present form with the understanding they will be revised, probably several times, in the coming years. 

By all means let me know if I've forgotten something useful and, even more importantly, if I've made a mistake!  A lot of other peoples work has been included but the mistakes are all mine!

GL and 73, Rudy N6LF, WD2XSH/20

LF-MF notes: 

Download Preface-Table of contents

Download Appendix 4- ground systems as reflectors

Download Chapter 1

Download Chapter 2

Download Chapter 3

Download Chapter 4

Download Chapter 5

Download Chapter 6

 

Universal curves for soil conductivity and permittivity

 

40 years ago Longmire and Smith suggested that the soil characteristics, conductivity and permittivity, which vary greatly with frequency, can be fitted to universal graphs.  The idea is if you know the values at one frequency you can predict the values at a different frequency.  I've had their report for many years but only recently took the time to carefully evaluate the idea.  Attached is a scan of the original report, Download Longmire and Smith scan, an EXCEL spreadsheet containing their equations compared to independent measurements, Download Longmire and Smith graphs   , and my comments on their idea,  Download Comments on Longmire and Smith .  The idea has some merit but you should decide for yourselves!

160m-2200m receiving antenna

The March 2015 QST article on a loop receiving antenna by DK6ED set me to thinking about a much larger version for 2200m and up.  In the process of scaling the antenna to my needs I realized that there several different operating modes (patterns) were possible which might be helpful in some situations.  The different patterns could be implemented with some simple switching in the shack.  I built that antenna and wrote an article published in Sept/Oct 2016 QEX: Download Sept-Oct 2016 QEX article .

Comments on Ed Laport's book

Some years ago I was asked if Ed Laport's book, Radio Antenna Engineering, gave reasonably accurate estimates for radiation resistance and current distribution for short verticals.  I did a short modeling study with NEC to see how the results compared with Laport.  Recently Neil Klagge, W0YSE, asked me if I still had these notes which had not been put up on this web page.  The following are my comments on the comparison between Laport and NEC: Download Comments on Laport .

QEX Appendices

I will have an article on radiation resistance and ground loss resistance for verticals in the July/August and September/October 2015 issues of QEX.  For anyone who wants more detailed background information for the article there are four appendices:

Download QEX Appendix A

Download QEX Appendix C

Download QEX Appendix D

GL and 73, Rudy N6LF

Radiation and ground loss resistances in verticals

Over the years I've had a continuing interest in vertical antennas and the many small details of how they work.  Most of the time the minutia are not of great practical importance but for those of us interested in more than casual explanations they can be very interesting.  Here is a two part QEX article on just such a detail, how the radiation resistance (Rr) and the equivalent ground loss resistance (Rg) behave as the antenna dimensions and soil characteristics are varied:  Download QEX Jul-Aug 2015  Download QEX sept-oct 2015 .  As mentioned in a earlier post, I can't put all the supporting details in a single article, it would become unreadable so I've put the supporting material into a series of appendices which you can pick through if you're interested:

Download Rr Study Appendix A

Download Rr Study Appendix B v2

Download Rr Study Appendix C rev 1

Download Rr Study Appendix D

630m Antenna Support Poles at N6LF

I have recently moved to a new QTH with several acres of clear farmland but no trees for antenna supports.  So I had to come up with a means to support a large 630m umbrella vertical and other experiments with wire antennas.  Here's what I did: Download Saginaw antenna support poles .