An exciting new antenna “design” by N3OX

A good antenna is one of the most important parts of your HF station, but there's certainly a bewildering array (pun intended) of options available to the new station builder or those who want to update their backyard metal farm for the better. You've got beams on towers, you've got verticals, and then you've got dozens of different wire antenna designs out there, commercial and homebrew, which claim all sorts of great “all-band” performance. This article is about wires. Ham radio has a long tradition of doing great things with some tall supports and copper strands, but how should you decide among the G5RV's and fan dipoles, the slinkies and windoms, the Sterba Curtains and stubbed, trapped, and loaded contraptions? . [Author ID1: at Sat Sep 20 14:05:00 2008 ]

[Author ID1: at Sat Sep 20 14:04:00 2008 ]

Well, I'm going to simplify things for you wire-lovers out there. I've spent some time with EZNEC to come up with a brand new antenna design that no one has ever built before, and I see a *lot* of promise in it. I would be absolutely thrilled if everybody strung one of these up in their backyard. I can guarantee that you will be able to make thousands of DX contacts on it if you install it as I'll describe. This antenna is really just another variation on the traditional open-wire fed doublet with some linear loading and off-center feed, but with at least one major advantage that I hope will become clear by the end of this article. Here's a drawing of the antenna from EZNEC:

FIGURE 1: The N3OX Wonder Wire

The antenna fits in a 60 foot wide by 20 foot high space. The models I'll show assume that the tops of all the letters are suspended about 40 feet above ground, but should work OK at lower height. Obviously, the details of the wire supports need to be worked out by the builder to accommodate what's available, but I think you could support it on a network of just five horizontal ropes spaced out evenly from 20 feet high to 40 feet high. Doing so will make the number “3” and the letter “O” a little blocky, but the antenna should remain readable.

This antenna should be fed with good quality 450 ohm window line about 1/8 of the way counterclockwise from the bottom of the letter “O.” (The letter “O” is actually a single turn helix loop in this antenna). The length of line isn't critical, but for the purposes of this analysis I'll assume 50 feet of line is enough to make it in to the shack. Of course, you need a high quality tuner with fairly wide range to feed any open wire fed antenna properly, but I think you'll find the advantages of this antenna make the investment worth it.

But don't take my word for it just yet. I want to back up my claims with some analysis. Let's look at some antenna patterns. I won't show patterns on every single band, because the overall trend is similar to a conventional doublet, more dipole-like on the lower bands and somewhat lobey on the higher, but again, I hope you'll find this antenna to be far superior to any of those. I know I do.

Here's an elevation pattern on 80m:

FIGURE 2: 80m Elevation Pattern

As you can see, on 80m at this installed height, the antenna provides a good NVIS pattern for local communications. You might notice the gain is down a little bit from what you might expect, but in the interest of honest disclosure, I ran these models with a realistically lossy 450 ohm feedline included. All antennas that will fit in a 60 foot wide horizontal space on 80m will have a somewhat low impedance, so the mismatch with ladder line can be quite severe. But we're only talking 3dB line loss and at most about 2dB tuner loss. And what's 5dB loss? I hear that's not even quite one “S-unit”. No one will ever notice that you're only radiating 32% of your output power.

On upper HF, the antenna really shines:

FIGURE 3: Great 17m DX Pattern

Look at that low take-off angle and great gain. This antenna has nearly 7.7dBi gain on the 17m band. That's practically like adding a 600W amplifier to that barefoot rig and lousy isotropic antenna you have installed now! Imagine the DX you'll work! [Author ID1: at Sun Sep 21 19:43:00 2008 ]

The pattern gets a little strange on the highest HF bands:

FIGURE 4: A Bug? Nah, I “Designed” It This Way

It pretty much looks like this on 10m and 12m too, but that's … um… uh… oh, yeah, that's a feature. I intentionally made it do that. For real, I swear. See, when you are operating 10m, 12m, and 15m for the next few years, the band will be opening mostly on trans-equatorial paths. So if you install this antenna so the lower HF dipole -like patterns point East-West to work many domestic and DX stations, the antenna concentrates your signal where the band is going to open anyway!

This antenna will certainly radiate a signal. With the exception of 80m, ladder line losses don't exceed a fraction of a dB, and according to W9CF's excellent tuner simulator, there's absolutely negligible (<0.5dB) tuner loss on 40m and up, and only a couple of dB on 80. But maybe I haven't convinced everyone to build this antenna. After all, you might be saying: “wouldn't *any* random wire approaching these dimensions work well and efficiently on 80 through 10m?” Well stop right there, don't let that negative thinking go a step further. Let me tell you the real advantage of this antenna, from my perspective. It's my callsign! There is NO WAY than anyone can call this antenna anything other than a “N3OX antenna.” I can build one, work DXCC or DXCC-and-a-half with it, mention that in the ad, and people will dish out $79.99 for a “N3OX antenna kit,” won't they? You antenna experts out there can't deny that the antenna “works” according to some rational definition. After all, with ladderline feed, efficiency is generally high, the impedances are easily matchable by modest tuners, and the antenna will fit in many backyards. And best of all, you'll stroke my ego and fatten my wallet every time you shell out your dollars for one, or at least you'll bring in banner ad revenue to my website every time you visit to look for construction plans.

OK, let's drop the farce. This antenna is idiotic. It's not that it doesn't “work,” because it will. It's dumb because it's complicated to build, it uses a lot of wire squashed into a small space, and it doesn't really show an advantage over a simpler design. In fact, it's systematically worse than a simple bent doublet that will fit in exactly the same space on a much simpler set of support ropes. Let's compare that antenna:

FIGURE 5: A Better Idea

This simple antenna is even a little longer than it needs to be for efficient matching on 80m. It clocks in about 5dB stronger (including reduced tuner loss) or 3.5dB excluding tuner loss than the N3OX antenna on 80m because it's got a higher radiation resistance and, I think, a higher effective height above ground. Upper HF comparison shows the bent doublet to be slightly better too. Here's an azimuth plot of the two antennas on 20m, taken at 18 degrees elevation (the takeoff angle of the N3OX antenna):

FIGURE 6: 20m Comparison

In some sense, there's nothing wrong with the N3OX antenna on most bands; if you actually were crazy enough to build it, you could fill up the log with great contacts. It's not really awful, just a little worse than the comparison, performance-wise. But make no mistake, you'd be a little off base if you were to attribute those great contacts to your great antenna, because what you'd actually be using is a mediocre, overcomplicated antenna that would be matched or exceeded by a much simpler antenna. Unless you're participating in the “Strange Antenna Challenge,” don't render my call twenty feet high in copper.

I'm not saying that all special-design multiband wire contraptions are nonsense. Some of them have real advantages; a proper, original G5RV, for example, is actually *designed* to present modest impedances on a number of bands at the twinlead to coax cable junction, allowing you to run coax into the shack without much loss. But there are also antennas out there that claim to be “experimental,” or “new,” or even “rediscovered” designs for wire antennas that aren't really designs at all. Just like the N3OX antenna, they're really just big random hunks of metal pressed into multiband service with a wide range tuner. If you take a closer look, you'll find there's just no reason to spend money on them or time on their meticulous construction. Random wire contraptions tend to work fine when you feed them with window line and a tuner, but if you're rolling your own or buying something, remember, much of what really matters is that it is big enough and installed high and in the clear. Just remember, there's a magic in ham radio that lets you do amazing things when you manage to radiate most of your 5W, 100W, or 1000W HF signal from any old mess of wire using low loss transmission line and a good tuner, but that doesn't make every tangle anyone has ever tried into a “design.”