I made a HB9CV antenna for portabel use. (2023)

I used a construction from “Antennenbuch” by Karl Rothammel, 10th edition.
On page 413 I found the description:

I used for 5 mm brass tube for the elements and a 10 mm copper tube for the boom. I soldered the elements to the boom.
The phasing line has to be lifted 3 mm above the element and boom.

I used the exact measures from the book, at first I made the elements a little longer to be sure, but the resonant frequency was too low (418 MHz) and with the exact measure from the book I got excellent results.

I have exchanged the trimmer with a fixed one of 3.9 pF and got the same result.

Here a SWR measurement with my NanoVNA V2.2 and the NanoVNA saver programme:

Marker 1: 432 MHz,      SWR: 1 : 1.289
Marker 2: 433.8 MHz, SWR: 1 : 1.024 min SWR
Marker 3: 438 MHz,      SWR: 1 : 1.807