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.
Antennas
The design of antennas is a rich field for investigation and innovation. Even after over a hundred years of work in the field we can still gain new insights and create ideas with immediate practical applications. Since I was first licensed over 50 years ago antennas have been my passion. Over the years I have published articles on antennas and continue to study and write about them. The purpose of this blog is to make this work available to those who might be interested.
In both amateur and commercial installations the transmitting and receiving equipment has become quite standardized and we rarely design and build our own equipment. The exception to that for me has been my participation in the ARRL 600m experiments where standard ham gear will not transmit. I've had to go back building some gear for this experiment. Antennas however, have much greater variety and provide a means for greatly improving station performance at modest cost. The "home brew" antenna is very much alive and well among amateurs. With a bit of knowledge and some hard work, the amateur can usually do as good or better than standard commercially available antennas and frequently at much lower cost. Many 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 since then 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 direct access to my articles and a venue for new work which will be added from time to time as I do more. Except for articles published elsewhere, much of what I'll be posting will be pretty 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 will emerge when all three techniques are combined.
If you're interested in verticals and ground systems take a look at the posts on ground system design and elevated radial verticals. For ideas on simple gain antennas for the low bands there are a wealth of ideas in the posts on single support low-band antennas and half-square antennas. For some practical insight on what to use for conductors in wire antennas take a look at the post on conductors for HF wire antennas. There are also articles on tower-antenna interactions and some information on my participation in the 600m experimental group. Most of the files for downloading are in .pdf format. The file sizes and original publication are noted after each.
October 17, 2006 in Introductory comments | Permalink | Comments (0)