ZL1RS - Antennas

A 9 over 9 stacked array for 2m


A stacked Yagi array for 2m - used here from 2019 until 2022

19 Dec 2019 ... the old 2m EME DXpedition array used at American Samoa - KH8 has been finally re-purposed as a 9 over 9 horizontally polarised array for 2m DX at the home QTH.

9 over 9 2m antenna array
19 December 2019

The 2m Yagis are an own-design on 4.8m long booms. They are stacked at 3.3m apart and combined with equal lengths of LMR400 phasing line to a 'power divider' made from 75 Ohm coax. According to the 4NEC2 antenna software, the stacked pair provides 17.5dBi of free space gain. The station feedline is LMR400 and I am usually using an FT-817ND driving a W6PQL 2m kitset PA producing 800W with a 40V supply (deliberately low Vdd to give some 'protection' in case there is an antenna fault).

Update: September 2020. An SWR fault occurred in the stacked Yagi array (according to the symptoms, probably an intermittent connector in the phasing harness or power divider). It could have been repaired with out much effort, but I took the opportunity to replace the array with a YU7EF 13 element 2m Yagi.

Update: 21 October 2020. The wind loading on the much longer Yagi at the top of the rotating mast was significant, causing the Yagi to move about alarmingly in strong winds, so the old 9-over-9 array was repaired (faulty "T" connector) and reinstalled on the tilt-over mast.

The rigid under-boom support tubes on the old array were replaced by 'top rope' supports to eliminate a mechanical resonance that caused the boom tips to flutter in certain wind conditions. Now the 9-over-9 array and tilt over mast are quite stable in any wind.

In addition, the main feedline back to the shack was upgraded from LMR400 (loss of 1.5dB/100ft) to LDF4-50 (loss of 0.8dB/100ft).

Photo 26 October 2020.
9-over-9 2m antenna array

Update: 10 August 2022. The 9-over-9 array was removed from the tilt-over rotating mast and reassembled temprorarily in it's original form (a portable 2m EME DXpedition array) as used at KH8 to try and work the D2TX 2m EME DXpedition. This was successful a few minutes after Bernie started opeeration (QSO at 17:44 UTC on 12 Aug 2022).

The 2m portable array has now been dismantled and packed away in it's DXpedition carry case ready for a possible future adventure ...

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