Antenna Design Software

Eznec

A new trend in Antenna modeling software is to build Antennas that are resonant! What do you say? Well in the early days of amateur radio nearly everything was matched by either,
a gamma match, beta match, hairpin match, 75 ohm 1/4 wave coax match, or one of a few hundred other home made matching devices.
With the advent of modern computer software, it was discovered that Yagi's, Quad's, and other normally non-resonant antennas could be matched to 50 ohm coax, by changing
the sizes and the spacing of the elements.

The above photo on the left shows how many Yagi's looked for 50 years, it was generally assumed that Yagi's were just low impedance antennas and had to be matched with some type of aiding device.
The above photo on the right shows how many Yagi's are being built today, and that they are perfectly happy with a 50 ohm coax running directly to it, as long as you do install a choke at that point.
The choke could be a Current Balun (preferred) or a bunch of Ferrite beads running on the outside of the coax for some length until the coax meets the mast at least. I know what some of you are thinking balanced to unbalanced, blah  blah blah....... NO.

Balanced to Unbalanced means there will probably be common mode current trying to run back down the coax...hence the choke. Even with  balanced
single element dipoles there is current that will attempt to run back down the coax, so you should have a choke in any case. On all antennas. The exception being on some raised end-fed verticals which actually need the coax to better balance the antenna electrically and give the antenna some "ground" path. see: A99 and Imax2000. The terms balanced and unbalanced are used frequently and vaguely in amateur radio on many websites, sometimes being used in completely different uses then described here. That's a long discussion in itself. But trust me ...you need a Choke regardless of your thoughts on balanced versus unbalanced.

Back to direct feed:
Is this really better than a matching device? Well all matching devices have power limits. Why? Well they have wattage limits because what's happening is the device is heating up as more and more power is running through it...it gets hot! Until it fails (melts), and thats your power limit! So if you are spending energy heating up coiled wires and iron , your not delivering power to the antenna. So is it better to have a direct feed to the antenna? YES.  How much loss is in a matching device....truly its anyone's guess...from .25 db's to 1 to 2 db's  have been quoted numbers, but I suspect it depends greatly on each design.
Is this enough loss to change out your antenna? That decision is up to you. In my opinion every little bit of loss you can eliminate can go a long way towards making the rare island contact one day. You just never know.

I would be remiss if I didn't mention the Steppir antenna company. Although certainly not new, they have been very popular and very good performers in the Yagi class. This Antenna through motorized elements changes the size of the elements depending upon what frequency your transceiver is tuned to, thereby giving you near perfect SWR on any band you choose to talk on. You can see the appeal.
No more SWR issues. These antennas work well, they are heavy and mechanically complex, expensive and are not without known issues. Having had a few of them 2... 4 element beams, Big IR, 3 element, I did like them. For the guy who is most concerned about SWR, these fit the bill nicely. Kind of a one size fits all antenna. They are not optimized monobanders, as the boom length is fixed and this cannot be best at all frequencys, as higher frequencys require shorter boom lengths and smaller element spacings then lower frequencys. Although they are good performers overall.

                                                                   

By far the biggest advanced in antenna building has been the advent of computer software designed to show you what the antennas pattern and gain will approximately look like with the parameters you put into it. This has been a big help for the amateur that decides to experiment with antennas and build his own. Like Me ! However there are some things you should know, before jumping into it.

The leader in this software revolution is called Eznec. Most (90%) buy or find the free version and some may even buy the $100 6.0 version. This free software was created 30 years ago. Thirty !!

To put this in perspective, Nintendo came out 30 years ago! Not Super Nintendo....Nintendo! Remember the original Duck Hunt ?  Well think of that software versus gaming software built today. No comparison.
Is there an new version that is up to date? Yes there is. That version is the PRO/4 version, which is updated frequently and is technology-wise current. So whats the problem?

Well most amateurs haven't blown the dust off their dollar bills that have been sitting in their wallets for decades, nevermind spending $1100.00 for the latest version of just software. Did I say $1,100.00    Yes I did. For that price amateur operators could buy a new Icom 7300!!  So they use the old version ( 30 years old version)  and think they are getting accurate results! They are not. Again think of a PC... 30 years ago versus today.
You sure you still wanna use that free software?

Ok lets get to it:
The pattern on the left is the Azimuth pattern, or the pattern of the antenna if you were standing high above it looking down at it. This is a beam antenna facing to the right or east if you prefer.
The pattern on the right is the Elevation pattern, or the pattern of the antenna if you were looking at it at ground level from the side. It shows mostly the forward radiation lobes facing to the right or east.
Amateur radio companies are starting to use these patterns to impress you in their catalogs or in monthly magazine publications, about their antennas. As with DB gain, these patterns can be manipulated to look great.

The overhead (Azimuth) is actually very very good. as most of the energy is heading forward , with little or no side lobes to be found, coupled with a small back lobe (decent Front to Back ratio).
However looking at the Elevation lobe you can plainly see all is not what it seems. Although not terrible by any means there are still several lobes other then the main lower lobe going forward, one at a 30 degree angle, and one at a 55 degree angle. These are wasted angles for the most part, as in most tough conditions such as distant groundwave or that rare Vietnam dx contact you want to get, the more energy you can get into the lowest possible lobe the better. This is often why if you do see an antenna pattern advertised , it will be pattern number 1 (on the left) and never the pattern on the right. Again the antenna height above ground , just like DB gain claimed by manufacturers can have a tremendous effect on what the pattern looks like. And manufacturers almost never will tell you that.

Ok so whats the benefit of this for the amateur radio operator who is NOT going to build his own antenna? Well once you get proficient with Eznec PRO/4 you can put in all the antennas you see and read about in magazines, once you know the dimensions and you can decide for yourself who is lying to the public on their claims or at the very least being deceptive with their claims. As you will have all the answers in front of you.

So if you have dreams or aspirations of being a Big Gun, you or someone you trust needs to have the updated version of this software, and then you'll know what your doing. Otherwise your leaving it to hearsay and what the manufacturers would have you believe.


                                                                                  


Last but not least the FANTASTIC HEXBEAM !   Wait didn't you say you like Cubical Quads?  I did and I do. But for the most bang for the buck this is the antenna that will get you on all the bands, and you will have a good performer. MFJ (if you trust them)  is making these very easy to buy. And you can even get the 40 meter version if you have the space. Hexbeams are lightweight, easy to turn with an inexpensive rotor, have very low wind loading, have low noise and work decent even at lower heights. ( this is a function of them almost being complete loops, even though they are two element antennas). You will get about 5.5 dbi of gain versus your 2 dbi dipole antenna, which can and most likely will be the difference in hearing that contact that you can't quite hear on your wire antenna. I highly recommend for the average amateur radio enthusiast. You can even build it yourself in about 2 hours time, all you'll need is a screwdriver. These aren't brand new designs, but new enough to include. The maker of this version G3TXQ has even underrated the hex beam antenna's performance a bit on his website compared to what I see in the newest version of Eznec Pro. And he's completely honest about the performance you can expect.

Now will you break every pile-up? No. Will you beat that guy you hate with the 4 element Cubical Quad or Yagi on the BIG tower he is always bragging about? No. Will you have a good chance of making thousands of contacts you would have never made before with a wire , vertical or small Yagi beam? Yes you will. Is it reliable? Yes. Is the SWR low on every band Yes. Will you grow to love it? Yes you will.

                                                   

     

 

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