RaDAR – The new ZS6BKW Maak Toe field measurements

I took part in the local 40m Hamnet contest this weekend using my FT817ND and 9:1 UNUN fed long wire hanging over a high tree branch. My deployment point was close to where I have hung the new ZS6BKW antenna (“Maak toe”), published in the March 2018 Radcom magazine by Brian Austin G0GSF, high up in the trees. I worked two SOTA stations during the exercise.

Propagation wasn’t the best so I spent some “Off time” taking some measurements on the BKW using the 817’s SWR indicator to determine “SWR”. I drew up the following chart as an indication of what the values looked like graphically. Note no tuner was in line.

The green values are for 40m and on the lower part of the band no SWR could be seen but started to lift halfway up the band at 7.1 MHz so the antenna is resonating low on the 40m band. Ideal for CW, Digital modes and SSB.

The brown values are for 10m and a dip in SWR can be clearly seen starting from 28.4 MHz where no SWR could be seen for at least 300 kHz and where the SWR started to slowly climb around 28.8 MHz. At 29.3 MHz the SWR indicator showed 5 bars. The antenna is resonating nicely on the SSB portion of the 10m band. A tuner will be needed for the CW and Digital modes portion of the band.

The yellow values are for 20m and best, but not low, in the CW portion of the band. A SWR indication of 1 bar is really not that critical but the antenna seems to be resonating below the 20m band.

The cyan values are for 17m and the SWR was hovering around 2 to 3 points which would definitely indicate the need for an ATU. The 12m band even more so!

All in all the antenna, in general, is resonating low and may need further trimming of the open wire feeder. I have already removed around a meter but the length is totally reliant on the open wire feed line’s velocity factor (VF).

This antenna was not designed for, and DOES NOT work on 30m and 15m.

The antenna lives in the trees ….. in KG34ac.

73 de Eddie ZS6BNE

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