With the waning sunspots and declining propagation on the higher HF bands (20 – 10), many guys are turning more to 40 meters. If they have a hex beam, they know how effective it is on 20 – 10 meters so the thought naturally comes to mind, “Why can’t I have a hex beam on 40 meters?”
This is a natural and understandable notion. So, why not?
The hex beam concept for 40 meters is a valid idea from a theoretical standpoint. There is no theoretical reason why a two element Yagi (which is what the hex beam is, essentially) won’t work on 40 meters just as it does on 20 – 10 meters. The problems come in the practical aspects of a 40 meter hex beam. Here are a few considerations to think about.
A hex beam for 20 – 10 meters is about 22 feet in diameter and weighs just under 30 pounds. But a hex beam for 40 meters is about 41 feet in diameter and weighs probably 45 pounds. Think about that. Do you have space for that size antenna? The typical support mechanism for a 20 – 10 meter hex beam is a steel push up mast that costs around $100. Could that mast handle a 40 meter hex? Very doubtful. For a 40 meter hex, you are looking at something more like a full scale tower to get it in the air.
The price of a 20 -10 meter hex beam is in the neighborhood of $600+. The cost of a 40 meter hex, because of the greatly increased structural requirements is going to be around $1,500.
You begin to see the practical issues involved in putting a hex beam up on 40 meters. Yes, it is possible and a few home brewers have done it. But no commercial maker of hex beams has successfully marketed a 40 meter hex beam for the reasons explained above.
The next question is, my tuner can get me pretty good 40 meter SWR on my 20 -10 meter hex beam. Wouldn’t that work then? You could probably tune your gutter system with some of the highly capable tuners available today, but low SWR doesn’t mean good performance in radiating and receiving. (Remember, you can put a 50 ohm resistor across your radio antenna terminals and get perfect SWR.) And application of high power on 40 meters to your 20 -10 meter hex beam causes very high voltages to develop on the terminals that could damage the beam.
Well, what about stringing a 40 meter dipole on the frame of my hex? You could do that of course, but the antenna modeling shows that there would not be much directionality on 40 meters; the 40 meter wire so configured is virtually omni-directional. It even requires a separate feedline. And unfortunately, it not only adds weight to the hex but it interacts especially with the 15 meter hex wires. So what is the point; why not just string the 40 meter wire in trees and leave the hex alone to do its work on 20 – 10 meters?
Bottom line, unless you want to buy yourself a large field somewhere, spend a fortune on a tower and go for a 40 meter hex beam or SteppIR, just use that 40 meter wire stretched between trees in your yard and do what the rest of us do. Live with it. If you just gotta have a bodacious signal, spend a few grand and get an amplifier.