What is the attraction of vertical antennas for HF?

Question

I understand that MW broadcast stations use vertical antennas because that polarization works much better for groundwave propagation. But in amateur radio, I would assume the focus for communications on the HF bands would be via ionospheric propagation, where the polarization doesn't matter a great deal.

As I contemplate what antenna to install next (after a simple inverted-vee hung out a second story window), I am struck by just how many articles/recommendations and even locals are using vertical antennas for HF communications.

The huge drawback to a vertical seems to be the ground plane required: instead of two light quarter-wavelength wires hung in various fashions across a yard/trees/attic, you instead need a sturdy tower for starters and as the icing on the cake, placement of dozens and dozens of fairly long wires all through your yard.

If you have room for a proper radial system, wouldn't you also have room for a decent loop or inverted vee? What is the attraction of replacing one of the "poles" of a dipole with dozens of almost-as-long radials instead?

Answer 1

Cribbing a few quotes from answers to related questions, here's a start.

From https://ham.stackexchange.com/a/195/1362:

The primary advantages of vertical antennas are that they are omnidirectional, and with an appropriate ground plane (radials) yield a low radiation angle; this reduces the number of "hops" that HF signals must make to reach their destination.

This makes a lot of sense: a horizontal dipole will have nulls off its ends, whereas the null of a vertical will point up into space.

From https://ham.stackexchange.com/a/494/1362:

At the lower end of the HF spectrum, the λ/2 height requirement for horizontal antennas can become cumbersome (even though a horizontal phased array may weaken this requirement by allowing somewhat lower heights). A vertical HF antenna can get away with a height of only λ/4.

This is something I keep neglecting to consider: that ideally (at least assuming low-angle radiation is the goal) a horizontal antenna needs to be really really high, i.e. twice as high as a vertical for the same band.

And of course the good old-fashioned https://ham.stackexchange.com/a/555/1362:

…the coax shield makes just as fine of an antenna as the dipole. It distorts the radiation pattern horribly, but since a dipole wasn't a directional antenna to begin, it hardly matters. It could mean that you get a lot of RF in the shack, but if you are transmitting with 100W this is unlikely to cause any serious problems.

i.e. sometimes the results of an "antenna" are actually the results of a long leaky feedline plus a generous amount of transmit power. Unless they are operating as loaded end-feds or something, this is the only explanation I can figure out for how HF verticals like the Comet CHA250B might be working in practice with no radials.

Answer 2

There are commercially-made verticals that are only 26 feet (8 m) high, that offer decent low-takeoff-angle (DX) performance on eight HF bands (and so-so performance on 80m), assuming that a good radial system has been installed. By comparison, a horizontally-polarized antenna needs to be up fairly high to have good low-angle performance. I seem to recall that a height of λ/2 or higher is recommended for dipoles used for DXing; that's often difficult to achieve for 40m and 80m. By the way, inverted vees have terrible low-angle performance for any direction other than broadside-on.

Any multi-band antenna is a compromise, but if you ask me horizontally-polarized multi-band antennas are more of a compromise than commercially-made multi-band verticals; G5RV-style antennas typically work well on five or six bands, but have two bands that the antenna isn't designed for at all. (Let's please not start yet another G5RV debate here.) Off-center-fed horizontally-polarized antennas can work well, but they make tremendous demands on the balun; when cheap baluns are used, as they often are, then the antenna's performance suffers.

In my opinion, the best reason to use a vertical is that vertically-polarized antennas and horizontally-polarized antennas complement each other so very well. When one works poorly, the other often works beautifully. If you only have a dipole or an inverted-vee up, then I'd advise you to try putting a vertical up also. You might be surprised at what the vertical can pull in that the dipole or inverted-vee can't.

Answer 3

One obvious answer is that a vertical antenna can be made to work in a very small area. The house where I live is a townhouse in a large city, and has basically no land. It is also close to power lines, and so a tower would be totally out even if I had space for one.

What you say about how a vertical can take up as much room as a loop, is true if you put all the radials down to make it work very well. But it can also be bolted on the back of a house with just a few bits of metal on the bottom to act as radials. It won't work as well, but if that's all the space you have then a vertical with a poor ground might well be your only choice.

Answer 4

Let me try to answer this part of the question:

If you have room for a proper radial system, wouldn't you also have room for a decent loop or inverted vee? What is the attraction of replacing one of the "poles" of a dipole with dozens of almost-as-long radials instead?

I will answer this from my own experiences, and decisions I made when constructing 3 verticals.

I have 3 verticals, one 9.6m high (120 radials of 4m), one 4.6m high (120 radials of 2.6m), and one 10m high with a T-top each leg 30m (120 radials of 4m). All of them have an auto-tuner at feed-point.

Why did I construct these ? -- here is my reasoning:

• I don't own the land and was given the use of 3 small plots of land to use.
• I did not get approval of the land owner to construct anything above 10m hight
• I did not get approval to go for planning permission for a tower
• I wanted to cover all HF bands for DX (low angles of radiation)
• I had enough copper wire for radial for zero cost
• I wanted the visual impact to be low
• I had a budget

Due to this I built verticals, I use them as follows:

• 9.6m height: 40m - 15m bands
• 4.6m height: 20m - 10m bands
• 10m-T: 160m - 80m bands (some NVIS properties when used on 40m)

I also experimented with:

• horizontal dipoles at 10m height
• inverted V center at 10m height
• loops, long wires, and various others

I believe a big part of the hobby is experimenting with antenna's, different designs, shapes, materials, and see what works for you, and what doesn't.

The question you are asking is not easy to answer with one single answer, and varies from amateur to amateur, with reasoning which varies as well.

For me: the verticals work, they were cheap to built and if they wouldn't have worked I would have taken them down and built something else for my QTH.

Built, operate try, built something else, rinse and repeat.

Answer 5

I have used a variety of vertical wires (usually NOT quarter wave length for any given band) with auto-couplers at their feed points as described above and agree totally with the author about their HF utility. Tall tree halyards and extended fiberglass poles have been my favorite ways to suspend wires. Hard to understand why so many folks don't like putting down the radial wires though. I almost never use less than 40 radial wires of 30-50 foot lengths on top of the dirt. That's true even when I operate portable in the woods of western Wisconsin every summer. The putting down and taking up of the radial wires in that portable setting are just part of daily exercise for the low back, essential for old codgers like me.

In sum, these are in my view great antenna systems if you put in a little upfront work. My favorite couplers have included the Icom AH-4, the SGC-230, and the MFJ-998RT (for legal limit power). I have ALWAYS used chokes on the coax lines running to those couplers, one at the input to the coupler and another one right outside the shack. The "DC voltage injector" used with the MFG unit works great--I have used it flawlessly with a 200-foot run of RG-213 in Vermont during winter ops.

Answer 6

The questioner mentioned "If you have room for a proper radial system...," which is generally 500 radials (well, maybe that's an exaggeration), buried, and at least 1/4 wavelength long at the lowest intended frequency.

But if the vertical's feedpoint is raised -- like 6 feet off the ground, or way up on the rooftop, it only needs 3 or 4 radials, which is at least simpler than dozens of buried radials when ground-mounted.

Someone mentioned 1/2 wavelength vertical. A traditional vertical is 1/4 wavelength, with 1/4 wavelength radials. A halfwave vertical is a possibility, such as a vertical dipole. Then the question might be, if you're going to center feed it, how you're going to deal with the coax slapping against the bottom half and radiation from the bottom half interacting in a bothersome fashion with the lower half of the vertical. Or if you're going to feed the vertical 1/2-wave at its bottom, how are you going to match the 50 ohm coax to the 2000 ohm bottom-feedpoint. The advantage of the halfwave vertical is that it doesn't require radials. A major disadvantage would be that it's twice as high as a quarter wave.

Answer 7

What's the attraction of a vertical? Pick one or more of these:

I already tried a horizontal dipole for 5 years. I no space to rotate the horizontal, and I wanted to try hitting the states in the nulls. I decided the tips of the horizontal were too close to the shack and I was getting direct radiation in the shack. The horizontal coupled with my phone line where the vertical doesn't. I've got space for a vertical but not for a horizontal -- and the ground wires are buried so nobody notices. I've only got one support, and a horizontal needs three.

I think the best answer for a ham is "already tried something else, time to try a vertical".