Antenna Modeling – The Practical Use

What do these software products all have in common:  EZNec, cocoaNEC, NEC 2, and NEC-Win?

1. They are intimidating, obscure, and un-intelligible software programs somehow related to Amateur Radio.
2. They each provide a means to use mathematical sets of formulas to simulate antennas in the "real world."
3. Electrical Engineers, PhD's, Nerds, and the socially unacceptable are the only humans who know the "secret and arcane" art of antenna modeling using these software tools.
4. These are very expensive software products, well out of the reach of a typical Ham.

No, the answer is not "3"; the correct answer is "2"!  Yes, really - I'm not kidding…

One of my favorite things to do in Amateur Radio is trying to model the "perfect" antenna.  I've "invested" (or wasted depending upon whom you ask!) a lot of time with EZNec (on Windows) and cocoaNEC (on Mac) and I really enjoy them a lot.  I've often asked myself questions like:

• I wonder what that dipole would look like in my back yard?
• What does a 3 element, 2-meter yagi do at 8' above the ground?
• How does a j-pole really radiate?
• Can I make my own Buckmaster (and save a TON of $$)?

Recently, I was able to put my "investment" (of time) to good use.  I'd decided that I wanted to put up a 40m dipole and remove the doublet that was in its place.  Sure the doublet worked OK, but I'd recently discovered just how inefficient that antenna radiates on it non-harmonic frequencies.  It doesn't really matter what "it" is, but I like things that work efficiently and my doublet surely didn't.

I had to opportunity to "design" my own dipole.  How tricky can that be you ask?  As tricky as you want to make it.  Since I knew how to use EZNec and cocoaNEC, I didn't just want a flattop dipole with it's 70+ Ohm feedpoint and 1.8+ SWR across the frequency band for 40m (see Figure 1).  I used cocoaNEC to model a dipole, sized for 40m, about 45’ above the ground – which was very close to my QTH’s backyard setup – to see what a regular dipole would look like.

Figure 1 - 40m Dipole "Flat Top"

Since the 40m antenna is lower to the ground than the optimal height, I started changing my model by changing the legs of the dipole.  I started off by slightly raising the legs by 10 degrees at the insulator and saw the feedpoint resistance drop a little.  Eventually, I managed to find a nice combination of dipole leg “angle”, based upon the height over ground.  I was also able to adjust the length of the legs to get the lowest SWR across the lower part of the 40m band.  The SWR model is show in Figure 2.

Figure 2 - 40m "V" Dipole

During November of 2012, I managed to find some time to hang my 40m dipole based upon the calculations.  I hung the wires and balun, trimmed, re-hung, trimmed, re-hung, etc. for a few hours.  When I was finished, I used my analyzer to see just how close I was.  Figure 3 shows the graph based upon the numbers my analyzer showed.  The curve is about as close to a match (compare Figure 3 to Figure 2) as I could ever expect!  I was so pleased – it has been a while since a project that I’m working on has turned out so well!

Figure 3 - Actual Analyzer Measurements at my QTH

As I’m writing this, I still can’t believe just how accurate the EZNec and cocoaNEC programs are.  I know it’s not rocket science, but I was able to design an antenna based on my requirements, build the antenna, and finally, measure to see that it matches the antenna design.

Once all the measurements were complete, I got right on the air.  The ARRL was having a Sweepstakes competition and the contacts were rolling in!  Perhaps band conditions were great or my antenna worked even better than I’d dreamed ☺  Either way, there were many contacts to be made!  It was a great way to end a weekend!

If you think that you’d be interested in trying to model your own antenna, RARC will be offering a 3 or 4 week “Introduction to EZNec Antenna Modeling” class in the late winter/early spring.

73 de KJ4WLH

2012 BSA Jamboree on the Air

2012 Boy Scout Jamboree on the Air (BS-JOTA)

Link to Pictures:

The BS-JOTA was held on Saturday, October 20th from 8:30 a.m. until 5:15 p.m. at the Cub Adventure Camp, located in Maidens, VA.  The BSA Heart of Virginia Council's Cardinal District held a Cub Scout "Cub Olympics" during the weekend of October 19th - 21st.  Approximately 1,200 Cub Scouts and their families camped during the weekend.

I'd like to thank the following individuals and sponsors:

• Richmond Amateur Radio Club (RARC)
• Sponsored the BS-JOTA station
• Provided HF equipment
• D-Star repeater access
• Richmond Amateur Telecommunication Society (RATS)
• UHF IRLP repeater access
• Cardinal District, Heart of Virginia Council
• Provided facilities for the BS-JOTA station
• Allowed the station to be part of the "Cub Olympics"
• Volunteers (in callsign order)
• KB4IQT - David Thomas - Troop 832
• KK4DWX - Bob Kendig
• N4CVA - Austin Thomas - Troop 832
• WA1UQO - Armand Hamel
• WA4SSG - Win Grant
• Mac McNeer(K4YEF)
• Use of the RARC Club callsign:  W4ZA

The BS-JOTA team set up an HF station, D-Star station, VHF/UHF station, and IRLP station over the day.  Contacts on HF were made all over the United States, Canada, and even over to Europe!  Austin Thomas (N4CVA), a Boy Scout was instrumental in showing the Cub Scouts how to make the "correct" contact - and MANY boys did make HF contacts throughout the day!  Austin did a fantastic job!

When large numbers of Cub Scouts showed up at the BS-JOTA station, Win Grant (WA4SSG) and David Thomas (KB4IQT) would take small groups a few dozen yards away from each other and they would use HT's to make contacts with each other.  Needless to say, a LOT of "local" contacts were made as well!

Armand Hamel (WA1UQO) brought one of the most fun instruments of the day - a key and code practice oscillator!  I believe Armand's key was the MOST USED piece of equipment - at least 100 scouts touched the key and the just LOVED making it squeak and squeal.  One "lesson" shared with the boys was teaching them how to say "HI" in Morse Code: ". . . .  . ."   The best part of having the boys learn to key "HI" was telling them that they could use their flashlights and do the SAME THING with the light - they could "talk" to each other in "secret code"!!  Big smiles, you could almost see the wheels turning in their heads as they figured out what they were going to do later that night.

The D-Star station was connected to the BS-JOTA reflector (REF033A) and occasionally to the Atlanta reflector (REF030C).  D-Star contacts were light as most of the operators were VERY busy helping the scouts talk either on HF or HT's in the small groups.  There were a lot of stations making contacts throughout the world on the BS-JOTA reflector:  Argentina, UK, New Zealand, and many others.  It was great hearing all the different countries and the accents of the stations were really interesting to the scouts as well.

As the afternoon wore on, the Scouts (and the operators) were getting tired!  The HF station was shut down and we linked the RATS UHF IRLP node to the BS-JOTA node (9091).  Scout after Scout after Scout made contacts primarily with other scouts in Canada and Texas.  At least 20 Scouts made contacts with other Scouts; and an occasional Ham as well - all over IRLP!

The day went great!  At least 50 - 60 Scouts made contacts with someone, mostly with other Scouts.  The day was beautiful.  The volunteers made the day go smoothly and were so generous with their time.  My final thoughts are these - I really enjoy ham radio and I also sharing my passion for this great hobby of ours with people who are open to new ideas!  We are the ones who make the entrance to our hobby "friendly" and "welcoming".  Get out there and "welcome" someone into your hobby today!

73 de KJ4WLH
Jim Bates, Troop 876, RARC Member, RATS Member

D-Star DVAP with laptop tether to cell - Amazing!

Last night I was sitting in my hotel room, thinking about how ridiculous it is that any hotel would charge $20/day for internet access.  $35 for "fast" service.  What a joke...

So, for the first time, I decided to tether my phone to my laptop and just use my cell data connection for my internet access.  Seemed to work OK, actually was better than I thought it would work.  In fact, I'm using it right now to update this page :)

Anyway, when I travel I always take my IC-92AD and my DVAP (red).  So, I got it out, plugged it in, and connected to the internet.  Wow, that was easy - it just worked (like I've grown to expect!)

My local club, Richmond Amateur Radio Club (RARC), located in Richmond, VA has a D-Star net that runs on Wednesday evening at 8pm (EDT).  I took a break from my Morse Code practice to join the net and it WORKED GREAT!

I've heard of folks using their cell connection in their car traveling all around the country staying in D-Star contact, but this is the first time that I'd ever done it.  It's more fun than it sounds.

So, no R2D2 during the net and it was awesome being able to chat with my buddies - just like I was local.

73 de KJ4WLH

RARC Presentation - Remote Operation

Well, last Friday night - August 10th, 2012, I had the opportunity to present in front of the Richmond Amateur Radio Club.  Talk about intimidating!  I'm a noob, all of 2+ years in the hobby and I'm looking out at guys with 30, 40, even 50+ years of radio experience - I mean, really, WHAT in the world am I able to tell THEM?!?!?!

The group was very civil, though I was nervous, and the presentation went along fairly smoothly.  I suppose one might say it even went well, but I still know there are some things that I would have done differently (and therefore better!)

Two buddies of mine, Armand (WA1UQO) and Tom (KC4CMK), and I re-installed a 20 meter antenna that had fallen a few years previously at the church where the RARC meetings are held.  That was really nice, part of my demonstration was receiving PSK31 on 20 meters while the club members filed in and chit chatted before the meeting started.

Anyway, I enjoyed discussing my experience with Icom's RS-BA1 software package and how I use it around the house and travelling.  There was quite a bit of Q&A and the presentation was very interactive - I guess that's the kind I like best, it keeps folks engaged in the conversation.

Here's a link to the Remote Operations presentation.

73 de KJ4WLH