Despite being a popular and productive way of simulating amateur radio antennas, another method of electromagnetic simulation makes use of the Finite-Difference Time Domain (FDTD) method.

Without going into too many details, the method divides up the simulation space into little cubes of volume. Then the next magnetic field values are derived from the current electric fields. Then the next electric field values are derived from the current magnetic fields. Repeat.

FDTD makes use of Maxwell’s equations to calculate the above fields. Being a Time Domain method, what follows shows a movie like display of what is happening in the antennas in super slow motion.

The cool byproduct of this style of simulation is we get to see a movie of magnetic and electric fields as power is applied to an antenna. The fields build up around the antenna and eventually fill the volume with energy. For both styles of hex beam antennas you can see after a few cycles how the parasitic element becomes energized. Once both elements are energized the beaming action takes place and you can see energy propagating forward.

Both simulation movies reveal the magnetic fields in the first 50 seconds and the electric fields in the second 50 seconds. They, of course, happen at the same time to yield Electro-Magnetic fields, but I could not show both in a meaningful way.

Here is a 10 meter Traffie (Classic?) Hexbeam…

Here is a 10 meter G3TXQ Broadband Hexbeam…

Neat eh?

No simulation technique is perfect, but the FDTD method’s ability to show EM in time is very cool.

If you are interested in FDTD, Google has quite a bit of information. There are some free tools out there for the taking.

One of the stations used an Elecraft K2 with an external power amp plus the 100 watt auto tuner. The Elecraft auto tuner provides two antenna ports. We connected a large dipole to channel 1 and left the other open for another antenna.

At some point during Field Day I decided things were going well enough for me to concentrate on my 20-15-10-06 meter hex beam of the G3TXQ variety.

As you can tell by the first photo below, the hex was hastily shoved into the trailer. However, I used good Flexweave wire for the elements and untangling the mess was straight forward. I decided the put the hex beam on the K2 station since it had the open antenna port and, for some reason, I think the K2 and the hex beam complement each other.

The hex beam was a bit loose in its rigging causing the elements to slump a bit. However, the thing tuned right up on 20, 15 and 10 meters similar to its debut during the Virginia QSO Party. Six meters was way off; I think the 10 meter wires were a bit too close to the six meter wires. No matter, the K2 had no 6 meters and 10 meters seemed to work well enough.

Results

Did it work? Boy it sure did. During my turn at the K2 Phone I found the hex beam provided two to four S units improvement against the dipole on 20 and 15 meters.

Late Saturday night I worked 4,800 mile contact with Hawaii (PAC) from Virginia with ease on 20 meters… on Phone! The Hex Beam and K2 bagged the only PAC contact of the four stations on site.

Several more 20 meter contacts were easily made to the West coast including LAX, SDG, SCV and WWA. I wish Field Day used Sections as multipliers, but I was glad to be able to add fresh contacts to the club’s totals. Tom, owner of the K2, quickly added many CW contacts using the beam.

The hex beam was up only about 15 feet and still worked quite well. Amazing.

We did have a rotator, but did not have it aligned with North. That was troubling, but I was just glad to be able to steer it at all at Field Day. We used a Channel Master TV type rotator. Yes, it works, but clearly is over stressed by the inertia of the hex beam despite its low mass. Anyone contemplating a rotator for their hex beam is well advised to “up” the rotator ratings quite a bit to ensure mechanical robustness.

Of all the compact compromise Yagi-Uda beam designs out there, I have to say the hex beam lives up to its own hype. There’s no magic in the hex beam (no matter what anyone tells you). It can’t outperform full size single band Yagi-Uda designs. However, for the investment, it is a superb value and deserves to be on anyone’s short list of antenna choices.

Choice Matters

The most important thing learned at this Field Day is having two antennas to select between makes a big difference in operating success. For some reason North Florida was alive with contacts and I sometimes used the hex beam and other times the wire dipole on 20 and 15 meters.

Yes, it’s Field Day and we tend to be minimalist. However, I designed this hex beam to be very portable and think it fits well with the Field Day theme with its simple tent peg tripod mount. It nicely complements a wire dipole.

The G3TXQ 20-15-10-06 meters Hex Beam antenna is a keeper for Field Days of the future.

So…

I have been eagerly absorbing all there is to know about the hex beam style of HF antennas.

If you are the least bit interested in building or buying your own hex beam a must read web site is the G3TXQ study of the hex beam…

One word that comes to mind is “WOW” what a great collection of tests, simulations and other thoughts about the hex beam.

My favorite feature of the site is the availability of an EZNEC simulation file for the G3TXQ of the five band broadband hex beam.

I eagerly downloaded the EZNEC file and, because I have the + version of the software with a higher segment limit, changed all the wires to a consistent and even segmentation rather than keeping the tapering feature. I now have 1223 segments in the mode. It takes a lot longer to do simulations, but is no big deal.

What I am doing with this beam is for another post. The question I hear often on the hexbeam Yahoo forum is concerning using the five band hex on 6 meters.

The focus of concern comes from the third harmonic of the 17 meter element which is close to the 6 meter band.

Indeed running a SWR plot on the stock five band hex beam between 48 and 56 MHz yields…

SWR of Five Band Hex Beam for 6 Meters

Hmmm, this is not a fantastic SWR, but sure suggests something in the five band broadband hex beam is absorbing the energy. Let’s see where the currents are…

Current Magnitudes in Five Band Hex at 51 MHz

Sure enough, the 17 meter element has the most current suggesting it is providing the majority of the absorption at 51 MHz. If you look closely, only the driven element has lots of current while the reflector seems quiet. If you look closer still you can imaging the 17 meter M element acting a bit like a folded Extended Zepp antenna. An examination of current phase indeed confirms that center current peak is of opposite polarity than the current peaks at the ends.

So this is all very interesting. The stock G3TXQ Broadband Hex Beam sort of works on 6 meters. Even if you can live with the high SWRs, is the pattern useful? The next figure shows the Elevation pattern of the five band hex beam up about 20 feet above the same ground as defined in the original G3TXQ file…

Elevation Pattern of 5 Band Hex Beam at 51MHz

Hmmm, not too shabby. Remember to not get too excited with gain figures of 8 dBi when simulating antennas above real ground; There is often a gain increase due to ground for any antenna including simple dipoles. The point here is this HF antenna seems to offer some gain at 6 meters. Here is the Azimuth plot of the 12 degree elevation…

12 Deg Azimuth of 5 Band Hex at 51 MHz

The front to back and front to side ratio is a bit weak at 5 dB, but this is certainly a directional antenna at 51 MHz.

My ultimate goal is to build a contest version of the broadband hex beam for just 20, 15 and 10 meters. After I deleted the 17 and 12 meter wires from the model, I ran SWR again to see if things change at 51 MHz…

SWR of 5 Band Broadband Hex Beam at 6 Meters

They sure did. The 12 and/or the 17 meter elements were certainly contributing to the dip in SWR in the 6 meter band. It is pretty obvious the 17 meter wires were operating at the third harmonic so I rule the 12 meter wires are not contributing to 6 meter operation.

So… what does the mean?

Two things.

1. If you have the five band 20-10 meter G3TXQ Broadband Hex Beam antenna, you may well have a workable 6 meter antenna too. If your rig has 6 meters on its HF output and a built-in auto-tuner, press TUNE at 51 MHz and see what you get. You may well have a free 6 meter beam ready for use.
2. Adding an additional 6 meter set of wires to the existing 5 band HF G3TXQ Broadband Hex Beam antenna, may be a waste of time since the 17 meter element is competing for some of the energy at 50+MHz.

The second point may surprise many folks who have invested in adding a 6 meter element to their five band hex beam. They say “it works fine.” That’s great, but it certainly is worth knowing why. In a future post we will simulate the five band with the extra 6 meter wires and see what we find.

Given the above facts, I will never add a 6 meter add on to the current G3TXQ Broadband Hex Beam design as it is clearly competing with the 17 meter antenna.

However, remember, I am building a three band hex beam with 20, 15 and 10 meters. This antenna won’t have the conflicting third harmonic issues caused by the 17 meter portion. I will explore the reasonableness of add 6 meters to my three band configuration in a future post.

Conclusion

For those of you with the 5 band design, you may well have a workable 6 meter beam an autotune button away from use right now. Give it a try and let us know the results by adding comments to this post.

There is an obvious conflict between an added 6m wire set and the existing 17m wire set which may create a complicated situation which looks “good enough,” but may be not what you expect. I would love to post your far-field 6 meter measurements of relative gain, front-back and front-side ratios. Please, no comments about how the hex beam is impossible to simulate.

Kudoes

I can’t thank G3TXQ enough for his extensive research into the hex beam antenna and his Broadband alternative. I very much look forward to building my contest version leveraging his excellent work.

This post is very late. The actual date of the events within it are just before March 2009 in preparation for the Virginia QSO Party.

In the many posts within this site, it is no secret my examination of various vertical antenna solutions with comparison between BigIR and the 43 Foot products a big part of this. Check out all the 43 Foot posts on HHD here…

43 Foot Antenna Selected
I chose the DX Engineering 43 Foot quick taper model during the price war between DXE and Zero Five. Compromises understood and simulations complete, I carefully considered the Big IR, but liked the idea of no moving parts or switches at the antenna location.

Back in Black
A bare aluminum antenna would stand out too much in my neighborhood so I decided to paint the antenna black. Priming aluminum is a topic I researched very carefully to be sure I applied a lasting finish. As shown below, I applied regular flat black paint over the primed aluminum pieces except where the pieces slide into each other; If you are going to paint your antenna, you need to mask the mating four or five inches of the lower end of each tube.

Conductive Compound
I used the recommended aluminum conductive anti-oxidant compound suggested by DXE on all physically and electrically mating aluminum surfaces. This results is a gooey mess the first few times you apply, but you get the hang of the proper amount soon.

Antenna Tilt Base – Cumbersome
The “kit” from DX Engineering included an Antenna Tilt Base which I gladly installed. It works great. However, you need to really watch what you are doing when lowering the antenna. If you do not seat the lower pivot bolt properly, you will bind it and/or the top sliding bolt and may simply cut it off.

You are well advised to pay very close attention to what is happening to your tilt base while moving it. If you cannot handle the antenna yourself, enlist the aid of a friend who takes direction well. The good news is you will get the hang of raising and lowering your antenna as you realize you will need to apply some downward pressure during transition.

Basically, you will need to hold the antenna nowhere near its center of gravity and manipulate it just as if it was not attached to anything; You and your two widely spaced hands are the antenna support, not the tilt base pivot point. This ensures you are able to “encourage” the tilt base bolts into the correct slots and keep them there during lowering. The 43 foot antenna is not too heavy, but, in my opinion is very cumbersome due to its length and floppy nature.

Photo Gallery

Radials
You probably noticed only eight or so radials on this 43 foot antenna system. Yes, I know… I need more and plan on installing more soon. On 20 and 40 meters, the feed point impedance is something north of 200 ohms (or something highish). It does not take many radials to create a ground resistance lower than that. However, 60, 80 and 160 meters are a different story. I will add more radials.

Performance – Good enough
With all the simulations I performed in EZNEC…

…I was not expecting more out of this antenna than possible. I knew it would be pointless for 10 and 15 meters. It knew it would provide good results for 20 meters. It would be close to a 1/4 wave 40 meter vertical. It would provide some results on 80 meters. It would stink on 160, yet still provide “something” to use for this difficult band.

In short, it has met all my expectations quite well. I now have one antenna that provides access to the major low sunspot HF bands while sacrificing 15, 12 and 10 meters during this sunspot low. This was the plan for the 2009 Virginia QSO Party and that’s exactly how it worked out.

Comparisons
I had a 75 meter turnstile antenna in addition to this 43 footer during the March 2009 QSO Party. The turnstile out performed the 43 foot vertical in almost every way on 80/75 meters. However, I did use the vertical to pull out one of our roving mobiles about 250 miles away during the QSO Party – I transmitted to him on the turnstile and received on the vertical; I would not have been able to work him without the vertical in the mix. For those wondering, I use the 8 port DX Engineering remote antenna switch – the smaller one – at the end of 240 feet of LMR-400 coax for my ‘antenna yard’ switcher.

40 meters was a bit of a toss up. Most of the time I used the vertical. However, I occasionally tried the 80 meter turnstile on 40 and it did work.

20 meters was tough due to a big DX contest the same weekend as the Virginia QSO Party. I had a tough time competing with the big guns. However, casual operating later revealed the 43 foot vertical does work pretty well on 20 meters.

Attempts at 15 and 10 meter contacts with the vertical are laughable. Zero success, but that’s not a surprise, thus I am not worried about it.

Conclusion
I am very happy to have this antenna. Except for certain times of the year, it is the only HF antenna I have available operating year round. For a single simple antenna (remember no moving parts), it provides at least some coverage on 160-20 meters with best results on 40 and 20 meters. Good enough for the moment.

However…

Those sunspots are coming back and I will lust after a solution for 17-10 meters very soon. My next project will likely be the hex beam as a simple solution for those bands. I will need some kind of support for this antenna which adds to the complexity.

When you compare the steps required to raise even a modest antenna like the hex beam, it is quite obvious no antenna solution will be as simple as the 43 foot vertical even after I took the time to paint it black.

The 43 foot antenna provides, for me at least, a very good value for the money, real-estate and simplicity. I would do it again and humbly suggest it to anyone who needs a single, simple, reliable, stealthy antenna and/or wants an additional “choice” for their antenna farm.

See you on the bands…
73

Ever since the 2009 QST article many folks, myself included, became aware of the simple elegance of the Hexagonal Beam (also known as Hexbeam generally and Hex-Beam® by Traffie Technology).

Indeed the simulated and reported performance of these Hex Beam antennas appears to be quite reasonable for the size. The “hex-beam” group on Yahoo has been buzzing away with discussion.

Originally an organization called “Traffie Technology” offered Hex-Beam products.

Another vendor came along with parts and kits for DIY hex beams at HexKit.com.

Then the QST article in early 2009, written by K4KIO, highlighted a different topology inspired by G3TXQ where the size of the frame and arrangement of the wires differ from the classic Hex-Beam to yield more broadband performance on each of the 20-10 meter bands with the burden of slightly larger size.

Each Hexbeam “style” is covered in superb detail at G3TXQ’s web site…

So the hex beam nuts had two choices of hex beam products: The Classic Hexbeam from Traffie Technologies and the Broadband Hexbeam created by G3TXQ and offered by K4KIO.

One of my favorite amateur radio companies, DX Engineering, came out with their own kit version of the broadband hex beam design called the Hexxagonal Beam.

So now we have four major suppliers of hexbeam kits and/or parts…

• Traffie Technology with the HEX-BEAM®
• HexKit
• K4KIO with the G3TXQ Broad band Hexagonal Beam
• DX Engineering with their HEXXAGONAL BEAM (a version of the G3TXQ)

The various names are humorous. Only Traffie Technology has a registered trade mark on HEX-BEAM®. DX Engineering is trying to claim trade mark on HEXX and HEXXOGONAL using Copyrights which is a bit bizarre. K4KIO discusses trademarks/copyrights on his site very briefly. Two of the three web sites reveal a surprising lack of understanding of what Copyrights and Trademarks are. Oh well.

With four competitors in the Hex Beam supply biz, I suggest the Hex Beam has arrived. These companies know you are out there and are competing for your antenna dollars. Traffie Technology offers the original smaller hex beam where both the driver and reflector are in the shape of a W; Traffie’s web site has a tech section which may suggest the Traffie version is not the classic, but something slightly different and more broad banded. K4KIO has the terrific QST article bringing attention to the G3TXQ broadband design. DX Engineering provides an excellent engineering background to the G3TXQ design stemming from their years of many well engineered antenna products; They have a spiffy new approach to the center base plate.

Look at each of their web sites and you will see the points they make in an attempt to win you over. This has better engineering… This has fewer parts… This has longer history… etc.

Note about Antenna Simulations
Note that some of the suppliers above, and many amateur radio antenna manufacturers in general, argue their antenna designs are not possible to simulate correctly in today’s NEC and other programs. Traffie mentions this on his tech page. Arrow Antennas told me the same thing for something as simple as their 440 MHz Yagi beam claiming no simulation works for their antenna.

Simulation has its limits and the lower cost versions of the available NEC programs often don’t have enough elements to properly model up something like the hex beam antenna, but it can be done with the more capable versions.

If an antenna manufacturer suggests simulations don’t match reality they either don’t understand reality, don’t understand simulations or are hiding something. No modern antenna engineering is performed without simulations (and of course real testing) these days. Antennas far more complex than any seen in amateur circles, including the hex beam, are successfully designed on the computer first with great success. Any manufacturer thinking their design can fool a competently modeled simulation of same is suspicious.

This does NOT mean these manufacturers don’t produce good quality results as hard core experimentation can and does work. Edison was weak on theory, but strong on trying everything experimentally; Edison experimented his way to success on several projects. However, Tesla was strong on theory. Tesla’s AC power system won the battle against Edison’s DC power system even before the first wire was laid down.

The point is Antenna Engineers howl at the idea any amateur antenna has supernatural powers that thwart decades old simulation abilities.

Its all good news though
The good news is the Hex Beam directional antenna in almost any form gives good performance in a compact package. In the end, we are the real winners. Go get you one…

Well, to be honest you may well have just as much success with a simple horizontal dipole strung up.

Dipoles are pretty easy to build and don’t cost too much if you would rather purchase one from Alpha-Delta or the Wireman.

However, if you…

• don’t have trees to support your dipole
• already have a dipole, but are interested in seeing if a vertical provides more performance
• have no antenna, but lots of property to try something new
• just want to try something different

…then this simple vertical antenna is for you.

The description on its construction are contained within the pages of…

It is nothing more than several sections of copper plumbing pipe available at any hardware outlet such as Home Depot, Lowes, etc.

The key to any practical ground mounted vertical antenna is radials, radials and more radials. I choose the radial concentrator plate from DX Engineering to organize my radial attachments. In my case each radial is 33 feet long, but since this is ground mounted, the radials are not tuned which means the lengths are not super critical.

I buried the coax between the house and the antenna.

As you can see…

16 foot vertical antenna over radial wires

…this antenna has a simple appearance. However, it works quite well on 20, 17 and 15 meters. I have a few 10 meter contacts too, but this is arguably the wrong band for an antenna cut for 20 meters.

Soon I will be putting up a dipole too since I actually do have a few trees of modest height. I am considering the Alpha-Delta DX-CC as a friend of mine has a large log from his. Plus, this will get me on 40 and 80 meters which is, at this point in the solar cycle, a good place to operate.

When I have both antennas I will do some simple AB comparisons asking:

• Does the vertical receive more noise as everyone suggests it might?
• Does the vertical provide better low angle performance?
• Does either antenna provide a benefit for certain bands and distances?
• Is a replacement vertical radiator such as the continuously tunable SteppIR BigIR vertical or the “tuner-required” 43 foot radiator several companies are selling something worth considering?
• Assuming I get a vertical with more bands along with the dipole DX-CC am I done with antennas for my QTH?

One of the things I love about ham radio is exactly these kind of choices.

Even though my radials are good and plenty, I realize the low angle performance is more reliant on the local soil conditions up to many wavelengths away from the antenna rather than anything I do with my radials. Still radials are there to ensure your antenna efficiency is good so you still should have plenty. Look up the excellent details on Cebik’s web site for more information before you try to understand what radials do for vertical antennas.

If you desire to try a vertical antenna, consider this simple copper pipe version. It is cheap, but does require quite a bit of radial wire. However, if you like what you get with your vertical antenna and want to upgrade to something better, the investment in your radial system will translate right over to your new antenna… and that antenna will love you for it.

UPDATE 2009:
I made my first, and so far only, Phone contact with Australia using this antenna on 20 meters. I was thrilled. This suggests simple antennas do work. However, I do admit the quad array of 20 meter beams used by the Aussie were the significant factor in our QSO

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.