Antennas By N6LF

Antennas

The design of antennas is a rich field for investigation and innovation.  Even after more than a hundred years of work in the field we can still gain new insights and ideas.  Since I was first licensed over 60 years ago antennas have been my passion and over the years I've published articles on antennas and continue to study and write about them. 

Amateurs rarely design and build their own equipment these days but antennas are very often home brewed and provide a means for improving station performance at modest cost.  60 years ago Tom Erdmann, W7DND(SK), told me that if I had $100, I should spend the first $90 on the antenna, the next $9 for the receiver and the final $1 on the transmitter. Of course prices have gone up bit but those proportions are still sound advice. I can honestly say I have a lot more money invested in my antennas than in my station equipment.

This web site provides access to my articles and a place to post new work from time to time. Except for articles published elsewhere, much of what I'll be posting will be informal and subject to change as I learn more. The work reported here is a mix of analytic (calculations), NEC modeling and field experiments on actual antennas. Each of these has it's place but the best picture emerges when all three techniques are combined.

Please note, I try to close each post to comments. Once in a while I forget to push the right button and a post may be open. However, I assume I'm perfect and always have the posts closed, so I don't look for comments.

A note on floating short circuited loops for inductor tuning.

In older equipment (circa WWII) we occasionally see a short circuited loop or small disc inside a coil to adjust the inductance.  This certainly works but has a bad effect on coil Q.  Attached is a very short note on a experimental test of this type of inductance adjustment.  Download Chapter 6 tuning loop note

Snubbers for Electronic Circuits

Some years ago I wrote a book on snubber circuits for power electronics.  Strictly speaking this is not a hot topic for amateurs but I thought it might help a few so here it is: Download Snubber e-book complete .  For those who don't need to know how to build the watch here's a much shorter summary: Download CD snubber design .

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

630m-2200m talk

I gave a short talk last night to some local hams on our new 630m and 2200m bands.  Here is PowerPoint file for that talk: Download 2200 and 630m Presentation -2   that's a .ppt file.  For new software using the .pptx format: Download 2200 and 630m Presentation -2 . 

LF-MF antenna notes

For many months I've been working on a set of design notes LF-MF antennas intended for hams.  I think the present draft, while far from perfect, may be helpful to many amateurs.  For that reason I've posted the notes 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 is included but the mistakes are all mine!

GL and 73, Rudy N6LF, WD2XSH/20

LF-MF notes: 

Download Preface-Table of contents

Download Chapter 1  LF-MF overview

Download Chapter 2  Simple verticals w/o top-loading

Download Chapter 3   Top-loaded verticals

Download Chapter 4   Inductive loading and multiple tuning

Download Chapter 5  Ground systems

Download Chapter 6  Tuning inductor design

 

 

The effect of insulation on wire antennas

Very often the wire available for an antenna will be wire intended for home electrical systems.  This will is usually insulated which raises the question "should we strip off the insulation?"  I took a very general look at this question using both experimental measurements and CAD modeling.  Here are my observations: Download Insulated Wire and Antennas .

In addition to the base article there are several referenced articles which give additional information:

Download Qex-ground-systems-part-2

Download Qex-mar-apr-2012

Download Qex-may-jun-2012

Download QEX Nov-Dec 2k antenna wire conductors

Download QEXJul-Aug 2016 BOG

 

 

Comments on the WD8DSB Bow-Tie RX

Don Kirk (WD8DSB) has developed a "Bow-Tie" terminated loop receiving antenna which is interesting.  I have some comments on it: Download WD8DSB Comments. 

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 .

Experimental validation of NEC modeling for low and buried wires

QEX July-August 2016  has a lengthy report on some experiments I performed to check on the validity of NEC modeling for low and buried wires: Download QEXJul-Aug 2016 BOG .

A summary of this article was run in QST June 2016: Download QST June 2016 BOG .

One important comment was omitted from these articles:

The function in NEC which models wire insulation works only for thin layers of insulation, i.e. < one wire diameter and even that is pushing it a bit. 

I tried to use this function to model buried radial systems with the wires in plastic tubes.  All I got was nonsense!  The EZNEC manual is very clear on this point but I couldn't resist trying it anyway!