7 Band Vertical for 10m to 40m
In my life as a Radio Amateur I loved to work holiday style from different Islands. Therfore I used wire antennas. But those antennas need trees or poles to hang it up. In the year 2023 I have been looking for vertical antennas.
This article describes an antenna for portable operation on 7 HF bands. The outstanding features are high efficiency and very low measurements in size. That give us the advantage to take it on holiday style DXpeditions. I used it as CT8/DL2MDU from Sao Miguel on the Azores in 2023 and as 9H/DL2MDU from Gozo Isl. with 5W QRP out of a (tr)uSDX in March 2024. In September 2024 it was in use on the Isl. of La Palma (EA8)
The Idea is from Joe Everhart, (N2CX). His full article can be read on the July 2017 issue of The QRP Quarterly. QRPGuys
had adapted his 40-30-20m portable vertical antenna design using
switched toroids for the base loading inductance into a lightweight
antenna for an easy outdoor setup.
Original Schematic
In the following lines I will show the parts of the antenna as well as the steps to build it by yourself. But first some theory to understand the working principle before starting with a bill of materials. The antenna is a quarter wave Vertical or Groundplane, made with a telescopic rod, two coils for the base loading inductance and four radials. See the circuit below.
My personal intention was to find a solution to use this genius working principle for 7 bands. Today are many materials available to make the radiator of the antenna adjustable. There are some antennas on the market with telescopic rods and adjustable coils. I decided to use a telescopic rod and two coils on toroids together with the two jumpers made from wires with alligator clips.
While the QRPGuys intended a lightweight low power
version of the antenna, I was thinking of a version for 100 watts+ with
acceptable weight and measurements for the drop off baggage. My choice
of toroids is the T184-2 (red) for L1 and L2. The enameled copper wire
is AWG 16 (1.3 mm) For the jumper cables I used silicone probe wires
with alligator clips on one end.
After a while there were suggestions from some HAM friends to change the design from two wires for the bridge to just one wire as seen in the diagram above. Thanks!
See some details on the following pictures.
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| Both coils in series for 40m |
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| The bridge cables are set for 10-20m |
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| The bridge cables are set for 30m |
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| 7 Band HF Vertical on the Azores |
