Perhaps he is right for many things, but for ham radio folks evaluating antenna choices a popular answer for the height of a vertical antenna for the HF bands appears to be 43.

Be sure to check out the many posts about the 43 foot antenna here at Ham Help Desk.

If you have been in the market for a vertical you have probably noticed the availability of a “tuner required” vertical which is forty-three feet in height above a reasonable ground plane of radials. Indeed Zero-Five, DX Engineering and others offer this exact configuration in their model lineup claiming “all band” operation from 160 to 10 meters. Can this really be true?

This is also known as a 13 meter vertical. Here is a discussion of why this compromise length exists with some pitfalls.

Forgoing the need for a tuner (which is arguably not too big a deal) let’s have a look at the predicted patterns using EZNec. To set up the simulation, I copied a vertical antenna with four radials from the Cebik model set available for purchase on his web site. The only thing I changed was the antenna height and the radial length.

• Antenna height = 43 feet AGL with the bottom about 3 inches above ground
• Four Radials of 1/4 wave each to simulate an efficient low impedance ground resulting from layout of many radials

I chose Cebik’s vertical example to ensure I leverage his knowledge of how to model radials reasonably well in EZNec which, in my case, uses NEC2 as the engine. NEC2 does not model underground radials so Cebik’s technique is a welcome insertion of NEC2 trickery. Plus, I wanted to capture all the appropriate assumptions he makes for vertical over radials EZNEC antenna simulation.

The antenna looks like this…

View of 43 foot vertical antenna in EZNEC

Now here is the predicted patterns using a typical frequency of the main HF bands. Note the “Primary” trace is the one plotted for the 10 meter band…

Patterns of 43 foot Vertical Antenna on the major HF Bands

The peak radiation angles and relative antenna gain for each bands are:

• ~ 5 dBi @ 57° for 10 meters – impressive, but high angle
• ~ 4 dbi @ 37° for 15 meters
• ~ 1 dBi @ 16° for 20 meters – nice low angle
• ~ 0 dBi @ 25° for 40 meters
• ~ -2 dBi @ 29° for 80 meters – this is quite functional
• ~ -8 dBi @ 23° for 160 meters – lossy, but it does work

Several things are apparent:

• The antenna has “better than nothing at all” performance on 160 meters and is certainly interesting for this difficult band.
• Low gain, but good low angle performance is apparent for 80 through 20 meters.
• The 15 meter band shows some actual gain, but at a high angle of about 30-40 degrees – This may or may not be what we want for our DX purposes on this band. That said, it is noteworthy to see it still has unity gain at lower angles.
• The 10 meter band, the black trace marked as Primary, shows peak energy well above 45 degrees elevation. I suspect this will be less than desirable.

You can see why the ten meter case has the high angle radiation when you look at the currents along the vertical as shown here…

View of 43 foot vertical operating at 28.3 MHz

The opposing current phases destructively interfere at some angles and constructively interfere at others.

Is this an all HF band antenna? Well, because it operates at no particular “tuned” length for any HF band, except maybe 60 meters, you will always need a tuner. So, sure, it can tune up anywhere the tuner (or matcher if you prefer) can match. If you have to have just one antenna for HF, maybe this is a good choice, especially during the current great low band conditions in this low sunspot point in time.

A better reason to consider this antenna is for reasonable 80-20 meter use and as a practical thing to try for the 160 meter band. Because you can tune almost anything to almost any band, it is possible to get 10 and 15 meter use too with the propagation issues described above.

Other advantages for this 43 foot antenna is expense. You can have one for a few hundred dollars and several major antenna manufacturers, noted above, make them. The variables between the manufacturers is likely strength in materials and other mechanical design issues. Look to Eham for evaluations.

In my quest for a do it all vertical to replace my 16.6 foot copper pipe my choices include:

1. Multiband Fixed Height Vertical using Traps
2. Multiband Variable Height Vertical using the SteppIR BigIR III
3. Multiband Fixed Height Vertical using an antenna matcher in the shack – such as this 43 foot concept
4. Multiband Fixed Height Vertical using an antenna matcher at the antenna base – 43 foot concept again
5. Forget the vertical and get a dipole

Because I am getting good results on 20 meters with my 16.6 foot vertical, I am not interested in dipole solution #5… yet. Thus, I desire to bring some closure to this vertical installation and make it the best it can be.

I am still leaning towards the SteppIR BigIR Vertical even though it is a bit expensive. Being able to tune the antenna precisely to the appropriate length is a great feature resulting is little standing waves on the coax.

However, the simplicity of solution #3 means no additional wires to the antenna to power an automatic remote tuner or drive the SteppIR motor. This is just radio (with built-in matcher), coax, antenna. I lose some power in my very long coax with the standing waves, but have a much more reliable system. Uncomplicated solutions are certainly well worth considering.

No matter what your choice, if you want a vertical, consider the investment you will need for the radial system. Get the DX Engineering Radial plate and just do it. It really helps.

One more point is worth mentioning. The various makers of 43 foot vertical antennas all suggest the use of a 1:4 balun. Some suggest using a balun model made specifically for “tuner use” with the idea these specialized units have the robustness needed to handle the less that ideal voltages and currents. A nice balun costs good coin and is certainly worth it. Just be sure to roll this expense into your trade study when comparing this 43 foot solution with something like the BigIR vertical.

Also watch out for aluminum components near the ground. Certain soil conditions will dissolve aluminum.

DX Engineering and Zero Five Antennas seem to be in hot competition in the vertical market and they both have an approximate 43 foot system to sell you. If you are in the market for this kind of vertical start your trade study with these two manufacturers.

Good luck.

For some while SteppIR has offered two vertical versions of this adjustable length antenna: one for 6-20 meters, the other 6-40 meters. Also, an optional base load coil option is available to extend band coverage to 60 and 80 meters.

The web site…

…offers an excellent view of what is inside the control boxes of the BigIR Vertical and the 80 meter coil.

You get an instant appreciation of how SteppIR Antennas, Inc. has addressed how to make an antenna element move in and out in an almost infinite number of positions using a stepper motor.

The 80 meter optional coil is also a clever way to extend the capability of this antenna to the lower bands albeit with compromised performance indicative of any “electrically short” radiator. This is, of course, due to antenna physics, not anything SteppIR Antennas, Inc. did.

The manufacturer’s web site…

…also shows a photo of the inside, but which does not immediately reveal this is a custom PCB switch using a PCB .

The 80 meter option assembly is very large and I began to wonder why.

Because the 80 meter option is a tapped inductance, as clearly shown in the photos contained in the web site referenced above, one might consider using high quality RF switches or relays to select the amount of inductance. A switch to bypass the coil entirely when using the SteppIR BigIR for 40 to 6 meter work is also sensible.

What the photos on the web site above made clear is SteppIR Antennas did not use RF relays to perform the select-coil-tap function, but manufactured their own switch using printed circuit boards arranged in a rotating contact switch operated by a stepper motor. Obviously, they are capitalizing on the great experience they have with stepper motors and the way they control it with their desktop controller.

As noted by the fine folks on the SteppIR email list, the coil taps have potentially large voltages that could easily arc over relay contacts when operating at higher powers.

My original version of this post forgot this important point. Now I understand why SteppIR went to such trouble to produce a very large switch with large separation between the “contacts” to handle the high voltages present. The cuts in the PCB material between each switch contact point reinforce this point.

The list of the issues with the 80 meter coil option include:

• Home-Brewish Inductor Tap Switch – The flimsy nature of this system still begs for a better approach, but I have to admit I cannot think a better approach in this price class
• Stiff wires on the moving switch contacts produce stress – high strand count wire may make better sense
• Weather exposed terminal connections for the stepper motor wiring – a good connector approach would be an option I would gladly pay extra for
• PCB trace-widths may not handle full power at the the 1,500 watt rating especially with the higher currents feeding the lower impedance of a short monopole. My calculations for 10 °C rise for the currents expected into, say, a 25 O antenna start at 0.1 inch with 2 oz. copper thickness. The PCB board has ample room for wider trace widths.
• Power off default potentially undefined

Soon I will post some details of suggested improvements to take SteppIR’s brilliant thinking into a better engineered approach.

A purchase of the BigIR vertical is a certainty for me. The enormous 80 meter option is a reasonable value at under $400 and would be a for-sure purchase if it wasn’t so large and I had not seen the inside home-brew switch. Still, the high voltage tolerance of SteppIR’s unique rotating PCB switch is, perhaps, a clever affordable solution that brings a good solution at a good price point… nothing wrong with that.

In SteppIR Antennas’ defense, product development can be quite a pain, especially when targeting products for notoriously stingy hams. The fact they have products for us to buy with their unique twist is a good thing for amateur radio.

To highlight their cleverness this is a best guess schematic of the RF paths…

The RF Paths in the SteppIR BigIR 80 m Option Coil

The most interesting portion of this schematic is the wiring of the coax wrapped toroid. It is another clever SteppIR design feature that helps match 50 ohm coax with the ~ 14 ohm impedance of a series inductance base loaded monopole antenna.

You are doing a good job SteppIR Antennas. With a few tweaks you will have a near perfect product. On the other hand, for the price you just might already have a near perfect product.

SteppIR, please take note… I would be delighted to pay another $100 for a good weather proof connector for the motor signals.