I bought the antenna from HFKits.nl1 (link at the bottom) as a kit. I agree with their sentiment that if you build it yourself, it holds no further mysteries. The product seemed to be composed and packaged with great care and it was a very pleasant start to an otherwise unknown hobby.
Now then …
Introduction #
The easiest way to get started on HF is to get a piece of wire in the air. The higher, and farther away from interference, the better. Unfortunately HF (full) wavelengths start at 10m, meaning antennas start at approx. 2.5m, but if you want to get higher bands (for some reason meaning lower frequencies) you need a longer antenna to effectively receive and transmit.
As my home is part of a row of houses, and not at the end, I could only work towards the end of my yard. And at the end of the yard there’s a large metal roof attenuating any signals. As such, I decided to use rope to suspend an end-fed half-wave antenna between the roof ridges, to get the maximum amount of height. This works reasonably well!
Building it #
After winding the 49:1 Unun1 (a transformer to deal with an unbalanced cable and an unbalanced antenna, and transforming the impedance 49x) and soldering everything together as best as I can, it was time to string it up and tune it. Using a slightly lower positioned attachment point of the house, I tuned the first part of the antenna to the 10/20m band, by connecting it to a NanoVNA and running an SWR sweep and then trimming off parts off the end. Ending up with an acceptable SWR (<2) on 10 and 20 meters.
You can shorten the length required for a resonant antenna by using a coil, but this will reduce the bandwidth. The kit1 came with enough wire and instructions to create a 35 μH coil using 80 turns of wire on a piece of PVC. Unfortunately I am apparently terrible at counting and after cutting off the end and asking my wife for a recount, I only got to about 71 turns. Using some of the spare wire off the end I was able to complete a few more turns, but this meant I also had to leave the additional end of the wire a little long (±2.05m instead of 1.85m). This made a total of a little over 12 meters.
When this was done, using a tennisball it was relatively easy to get the rope across both roof lines and onto the other side.
Tying off each end of the antenna to the two ropes (one from either side) and pulling it taut yielded the desired effect. Mounting a frog or cleat was enough to secure the rope on either side.
Bringing the coax inside is another story.
SWR measurements #
The measurements below have been taken with a NanoVNA and the nanovna-saver2 software
It’s not perfect, but it’s mine. The tiny red, green, and blue triangle indicators indicate the middle of the 40m, 20m and 10m bands. Judging from the location of the 10m and 20m dips, the wire is slightly short. The 40m (with a coil) is slightly long and dips in the early part of the band where most of the CW happens.
While the 80m band still tunes on the G90, it has an SWR of more than 9:1 by default. Surprisingly though the 160m tunes really well and is between about 1.6:1 and 2.5:1 .
Detailed SWR readings per band. The grey background is the actual amateur radio band, with 10% on either side.
