A Ham Radio Series 32 - Some Antenna News and Rambling

The big thing I want to mention is something that I think some people will want to take advantage of.  I've written about antenna analysis programs before, including posting some data I've derived with the one I use, EZNEC by Roy Lewallen, W7EL.  Last year, Roy announced he was going to retire this year and that he was going to do one, last, big update to EZNEC and post it on the web site as a free download.  

He didn't quite make the first of the year, which (ISTRC) was his goal, but it's there for the free download, along with a lot of his collected wisdom from over the years.  There are manuals and other links there - everything except actual customer support.  The nice thing about a program like EZNEC that has been around for a long time is that there are tons of experienced people out there and using your favorite search engine to look for specific questions can help.  I'm by no means an expert but I can usually get reasonably believable results.  

While I have several plots of EZNEC outputs linked to in that first paragraph, I thought I'd show you the essentials of working with it.  These are all separate live windows on your screen and I grabbed three I'd use among the most.  The antenna is a design for a 5 element, loop fed yagi for six meters that I had been thinking of building until I decided to buy a different design that I talked about around the first week of the year.

The design of the antenna is the lower left window called "Wires" - although they don't have to be wires.  Look at the fifth column from the right edge, called diameter, where you can see all of these are big enough to be tubes.  You simply enter the locations of the start and end of the wire.  The upper right window is the model that has been entered and if you look at the middle option of the bottom box on that window, you'll see an "Add Conn Wires" option.  This allows you to draw the wires onto the diagram with your mouse, left button to start a wire, right to end it.  You'll see two short wires connecting the ends of elements 2 and 3, pointed perpendicular to every other wire - I added those this way.  I haven't tried drawing an antenna from scratch that way.  

There are tons of antenna files that can be downloaded to start with from various places online, and it comes with some samples, too.  Say you want to put up a dipole.  All you need to do is find a file of a dipole and change the dimensions to suit what you're putting up.  I think it came with some dipole files.

As I've said many times, all of my antenna projects begin with the phrase, "when it cools off," because I just don't want to work outside all day for at least half the year.  We have maybe a month left, possibly as much as two months, and I'm working to complete things I wanted to try.  I can work on some projects year 'round because they're entirely indoors.  I tend to think of them as winter projects, too, in case they make me to do a lot of work outside.  

To that end, I've been playing with another version of what I've done to my vertical antenna before, which is to add a matching circuit that will allow it to be used on the 160m ham band.  To accomplish that, I need to get the antenna under 3:1 SWR across the band and then the radio's built-in tuner will match that.  

The vertical itself is sold as an 80/40 dual band antenna and I currently use it on those and 30m.  The trick I did in that old post worked, but it only had a bandwidth of about 50 kHz, on a band that's 200 kHz wide and it wasn't really tunable.  I've been playing with analyzing alternate ways to match the impedance of the antenna and while I have improved on that performance, it's not there, yet.  I haven't built the circuit to compare reality to theory but the analysis shows it should be under 3:1 for around 150 or 160 kHz.   

As I said last year, I know if I called this post “Putting the Cushcraft MA8040V on 160 Meters,” I'd get a whole different bunch of readers.  Maybe five or ten new readers.