Verticals
Over the past months, Ivy and I have been trying to catch those DX stations. In the current time of solar minimum, it has been hard to return to the calls with our meager 100W. And, not being able to afford stacked monobanders and a leenyer, we’ve decided to try and improve what we can, which is antennas.
The first choice was to install HF verticals for different bands. Since they are relatively easy to construct with just wire, and have a low take-off angle of radiation, we decided to go for it.
Wonky 20 metre vertical
First was a 20 metre vertical. Scrounging around for parts, we came across a sad piece of copper pipe that had been left outside for some months. After straightening it out the best we could, it measured just over 4 metres in length. My understanding of antennas isn’t all that great, but I do understand velocity factor. Copper pipe is said to have a VF of 0.86 or so. Given our poor copper was in an advanced state of oxidation, I figured the VF would be lower.
Oh well, might as well just load it up and see. After sanding off the corrosion on the bottom and attaching a strapping wire via a clamp, it seemed to have OK continuity. Then we decided to try 4 radials of scrap wire, each at 1/4 of a wavelength. The vertical was then installed on the roof with surprising results. Though we could not get the SWR down below 1.7 or so, it happened to have this dip at ~14100kHz. This antenna performed quite well, considering it cost us the grand total of naught
With the success of 20 metres, we decided to again try, this time on 40 metres. Around this time we decided to buy one of the EMDRC 9 metre aluminium masts. While it’s a tad short for the 10 metre tall 1/4 wavelength vertical at 7MHz, we came up with a clever solution to extendorise the mast. Using a 3 metre long bit of orange electrical conduit, we slid our extender into the top of the mast section. The whole thing flopped right over to one side. But hey, the radiating element can’t be too close to the metal mast anyway, else it will couple and cause a distorted radiating pattern and possibly effect impedence. The bendy conduit put the vertical about a metre and a half to one side of the mast, and the bottom of the 10 metre radiating wire ended up just above the ground. More 1/4 wavelength radials, and we were on the air. This one, though, was able to be tuned by way of changing the length. We managed to bring the SWR down to about 1.2:1 at ~7200kHz.
Results with the 40 metre vertical weren’t as drastically increased as with 20 metres. We got only slightly better (often only 1 S-unit) signals on the vertical compared to the dipole. The radiation pattern for transmit seemed to be pretty similar to the dipoles as well. It was useful as an antenna for local contacts, but we still couldn’t get those DX stations to hear us.
We’ve since given up on the verticals, in favour of a ZL-Special. There will be more to come.
73, Hannah
