Atmospheric noise is generally verticallypolarized. This is the noise you hear when there is no signal present at the frequency you are tuned to. Atmospheric noise is a combination of noise from such sources as lightning strikes around the globe (especially cloudtocloud strikes) and cosmic noise (aka galactic noise).

Don’t confuse this with the noise you might be receiving from a manmade device, such as a plasma TV, wireless phone charger, wallwart power supply, laptop power supply, etc.

Atmospheric noise will always be present in the HF radio spectrum, to varying degrees. The noise is more intense at the lower frequencies (40m and lower) and diminishes more and more as you move up from 14 MHz. The noise is practically gone in the VHF spectrum and above. That’s when you start hearing the thermal noise generated by your receiver. And that’s when a squelch comes in handy.

Since atmospheric noise is verticallypolarized, a vertical HF antenna will naturally receive more of it. A horizontal dipole antenna will not receive as much atmospheric noise, since the horizontal dipole is horizontallypolarized.

So why use a vertical antenna? The vertical antenna produces a low angle of radiation, concentrating more of your signal toward the horizon. Your signal will travel a greater distance before being refracted (bent) back toward the Earth. The vertical antenna can do this even if it is groundmounted. Note that, for safety reasons, I prefer to install my vertical antenna around 12 to 15 feet above ground. I use a vertical antenna that includes radials, so I don’t need to bury wire radials in my yard.

The other advantage of a vertical antenna is that it usually takes up very little horizontal space, compared to a horizontal dipole. So the vertical is great when you are limited by the size of your property.

Wouldn’t it be great to have the lower noise of a horizontal dipole with the lower angle of radiation (aka takeoff angle) of a vertical antenna? That’s why we need to install a horizontal dipole at 1/2 wavelength or higher above the ground beneath it. In the case of a multiband dipole, install it 1/2 wavelength above the ground according the the lowest band it will operate on.

In this video I’m tuned to the 15meter band. The 15 meter band usually has less atmospheric noise than lower frequency bands. Remember, the lower the frequency the higher the amount of atmospheric noise. But a vertically polarized antenna will tend to pick up more atmospheric noise than a horizontal antenna does, even at 21 MHz. I tuned in to listen to a DX station on the 15m band and I noticed the band was more noisy than usual, primarily due to intense lightning activity in my region and beyond. This video will illustrate how I can improve the S/N ratio by switching to a dipole.

You will also see an example of the vertical picking up the most noise and the least signal. But don’t interpret that as meaning the vertical never wins. Sometimes, under certain propagation conditions, the vertical wins the signal strength contest, especially on 10, 12, and 15 meters. It just tends to bring in more noise with the signal.

I could use the dipole for RX and TX with the vertical. But I should mention that the dipole in this video (ZS6BKW) can sometimes even outperform my 160m Doublet on the 15m band. There is an example of that in the video. But of course the ZS6BKW is in the doublet family. It isn’t 250 feet of wire, like the doublet; it’s around 94 feet of wire. My ZS6BKW came from www.NI4L.com. Chris Fox makes the best version of that antenna that I’ve seen. It is resonant at 29.6 to 29.7 MHz, plus the 12, 17, 20, and 40 meter bands. With a widerange antenna match, it can function on 6 through 80 meters.

Note that the vertical in this video, the Cushcraft R5, was discontinued many years ago. The nearest match that is available today is the Cushcraft R6000. It adds the 6meter band to the mix.

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