Antennas By N6LF

QEX article on elevated radial ground systems

Elevated grounds systems are frequently used in place of wires on or in the ground under a vertical.  This kind of ground system can work very well but when there are only a few radials in the elevated system it can be very sensitive to asymmetries in the radial fan, nearby conductors, etc.  Here is an article which was published in the March/April and May/June 2012 issues of QEX magazine which takes a much closer look at elevated ground systems than has been done in the past.  In the end the advice is very simple: use more radials!  This is the same advice I give for systems on or in the ground.  The standard 4-radial elevated system can work well but as the article shows it can also work not so well.  The article is primarily intended to show why I suggest that 10-12 elevated radials should be used if possible.  Download QEX Mar-Apr 2012 , 1MB, Download QEX May-Jun 2012, 2.4 MB.

Some comments on chokes for 160m GP verticals

Recently I was asked about air-core coaxial chokes to be used for feedline isolation on a 160m ground-plane vertical.  The following are some comments I made: Download 160m common mode choke 

comments on elevated radials

I recently sent a note to the QST technical correspondence editor at the ARRL concerning the effect of radial system asymmetries in elevated radial systems.  You can read this letter at: Download December 2010 letter to QST technical correspondence .  This note emphasizes some of the problems with elevated systems and some possible misinterpretation of my March 2010 QST article.

After sending this note I realized that there was a lot more to say on the subject.  So I'm in the process of writing a very extensive article on elevated wire ground systems and the effects and cures for asymmetries.  That is however, still couple of months away from being finished.  I will post it here when it's done.

73, Rudy N6LF

ground systems for DXpeditions

I received an query from Bill, N7OU, regarding ground systems for multi-band verticals over saltwater.  My reply to him can be found at: Download Seawater ground article .

73, Rudy

Relation between vertical height and radial length

In one of my earlier posts I had some information on the relationship between vertical height and optimum radial lengths.  That information was buried in a larger document discussing several other items an was not that easy to find, so I've pulled that discussion out as a separate download: Download Vertical height versus radial system .  What it shows is that there is a case to be made that, for a given total length of wire, more numerous shorter radials can be helpful on short verticals.  At least up to point.

QEX letter to the editor

I recently sent the attached letter to the editor of QEX.  It may answer some questions and correct some incorrect figure captions: Download QEX letter to the editor 1 

Series of QEX articles on ground system experiments

Last year I posted results from a series of experiments on ground systems for vertical antennas.  That series of reports was converted with some modifications into a series of seven articles in QEX magazine.  The ARRL has kindly given me permission to post .pdf files of these seven articles for those who do not have access to QEX.  Here they are:

Download QEX ground systems part 1

Download QEX ground systems part 2

Download QEX ground systems part 3

Download QEX ground systems part 4

Download QEX ground systems part 5

Download QEX ground systems part 6

Download QEX ground systems part 7

A summary of these articles was published in QST for March 2010, pp. 30-33. 

In QEX for May/June 2010 letters to the editor I made the following comments.  "I think too many people are taking the QST article as gospel when it should be viewed only as an interesting set of expriments which shed some light on a few questions.  Even the QEX series, which is much more detailed, raises far more questons than it answers.  I was really hoping to encourage others to expand on my work (as I expanded on Sevick's) by showing how it might be done.  73, Rudy N6LF"

Pacificon 2008 presentation

On Friday October 17th I'll be giving a talk at Pacificon 2008 in San Ramon, CA.  The talk is just an overview of my recent ground system experiments.  Here is a copy of the presentation for those who attended or have an interest:

Download pacificon_2008.pps

Are the lengths of radials related to the height of a vertical?

I first posted this note some weeks ago with information on the relation between vertical height and radial lengths.  However, that information was buried in one of the attachments.  To make it easier to find I've extracted the parts relevant to radial length versus height and they are now a separate and much smaller download:  Download Vertical height versus radial system .

A couple of weeks back I noticed a question on the TowerTalk reflector about making the radials on a vertical the same length as the height, i.e. use shorter radials on shorter antennas.  Something along these lines has been "conventional wisdom" for a long time but I'd never seen any real justification for it.  So I did a quick modeling study and up to a point it does seem to support this idea.  I wrote this up in:

Download radial_system_design_and_efficiency_in_hf_verticals.pdf

While I was at it I took a look at the variation in radiation resistance and ground loss resistance as the radial system and/or ground characteristics were varied:

Download radiation_resistance_variation_with_radial_system_design.pdf

This one is just for fun, I don't think it has much practical application but it may help in understanding how verticals work.

HF vertical ground systems experiments

Over the years I have talked a lot about ground systems for HF verticals. Most of what I have said comes from modeling and calculations of my own and experimental work of others most of which was for LF or MF broadcast applications.  Other than the QST articles by Sevick many years ago and the CQ articles by Arch Doty, there has been little experimental work reported in amateur literature which could be used to judge the validity of NEC modeling and whether it can actually tell us something that's real for HF verticals.  Beginning about a year ago I set up a test range in my pasture and began a series of careful experiments on HF verticals with various ground systems including some with elevated radials.  Two results stand out.  First the NEC prediction that a few elevated radials can be as efficient as a large number of ground radials seems to be correct at least at my site with the test antennas I used.  See experiment 3.

The second interesting item is that using only a few long radials can result in much higher ground losses than the same radials shortened.  In the past I have often said that a few long radials might be a waste of copper but were harmless.  Not so! Experiments 4 and 5 are related to this.

I also ran some experiments with the 40m+ version of the SteppIR vertical.  My particular interest was developing a ground system that was effective from 40m through 10m.  That work is reported in experiment 6.  Some obvious ground systems don't work all that well.

I have written up my experiments in a series of reports.  Nothing formal just a review of the experiment, the results and some comments. 

Download antenna_ground_system_experiment_1.pdf

Download antenna_ground_system_experiment_2.pdf

Download antenna_ground_system_experiment_3.pdf

Download antenna_ground_system_experiment_4.pdf

Download antenna_ground_system_experiment_5.pdf

Download antenna_ground_system_experiment_6.pdf

Separate from the reports I have written up a detailed description of the test arrangments and instrumentation:  Download antenna_ground_system_test_setup.pdf

I suggest you read the test setup description first so you can follow the experiment reports which do not contain all the test setup details.

On Saturday, August first, I gave a talk to the NW DX convention on this work.  The following is the PowerPoint presentation file for that talk: Download ground_system_tests.pps