Tag Archives: fan

Nested Quarter Wave Vertical Antenna 20m and 10m

20m 10m verticalWith my recent success at building fan dipoles that are more “nested” than “fan”, I saw no reason why I couldn’t put up more than one element on my 20m band vertical to achieve a match on 10m. I ran up a 2.4m length of D10 comms wire up the side of the pole, around 2 inches away from the 20m quarter wave element. After trimming a few centimeters here and there, it tuned it at 1.3:1 SWR and all was well.

To make sure everything really was good, I applied a QRO carrier and watched in amazement as the SWR hovered for a few seconds before moving up and down and finally going off the scale with the Acom shutting down with an alarm (what a great amp that is!).

It took a while to track this down but it turns out the D10 military comms wire had melted at the guying point about half way up the 10m vertical element. I had tensioned it around one of the bolts on the steel three-way guy point to stop it flapping around and it decided to try melt the insulation and finally and weld itself onto it before blowing itself apart. The joys of QRO.

Under the hood, “Fan Dipoles”

10m and 15m nested dipole

10m and 15m nested dipole

Last year, with the assistance of Stu, M0NYP, I built a fan dipole out of D10 military telecoms wire for 80m, 40m and 20m for club field days. There was a fair amount of gap between each element, probably about 5 to 7 degrees becasue that’s what I thought you should do. For those people who came to either the Avoncroft Mills on the Air day, or the SSB Field Day, will recall the antenna. However, we lacked 15m and 10m though which I found a disappointment.

To become “all band”, I considered adding more elements to the Field Day antenna but experience has taught me that multi-band wire dipoles have a tendency to get tangled in the field. Adding more elements would probably just mean more tangles = less fun. In a Field Day situation, that’s a frustrating day out.

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