SOTA – 23 and 13cm from Mt Coree

Sunday 20 January 2019. Mt Coree (QF44JQ) 1421 metres ASL, Namadgi National Park, Australian Capital Territory

GPS track route is available here

“272 km via an A380 aircraft enhancement reflection en route to Sydney”

Mt Coree at 1421 metres ASL is a premier location for VHF-UHF Dx operations. Mt Coree dominates the Brindabella Ranges with it’s impressive granite structure with sheer vertical cliffs. The 360 degree view is commanding and for VHF-UHF radio purposes there are no vertical obstructions to the horizon. The summit is perfect for long distance (Dx) VHF-UHF-Microwave radio contacts out to VK2 and VK3.

Tony VK1VIC and I are undertaking a SOTA activation of Mt Coree. Tony is operating on 14 and 7 MHz and is very keen to qualify using CW mode. To qualify a SOTA summit the activator must complete valid signal report exchanges with a minimum of four unique callsigns. There is no upper limit to the number of stations worked on a SOTA summit, however for practical or safety reasons the activator has the choice to terminate the activation when deemed necessary.

VK1AD SOTA shack at Mt Ginini, Namadgi National Park

Equipment at the summit

  • SG-Lab 23 and 13cm transverters
  • FT-817ND
  • 13 volt 4S 8.4 Ah LiFePO4 battery
  • 2m/70cm dual band yagi
  • 23cm 1296 MHz Bi-Quad antenna
  • 13cm 2.4 GHz Bi-Quad antenna
  • 70cm 433 MHz flower pot antenna
  • 2 x 1.4 metre tripods
  • Lenovo 7 inch tablet
  • Flightradar24 software
  • Compass
  • Backpack, food, water, first aid kit

2m/70cm Dual Band Yagi & 23cm Bi-Quad at Mt Coree

View east to Canberra, cloud covering the summit


Cloud descends on the summit

View west over Brindabella National Park


Hombrew 13cm Bi-Quad antenna

View south-west


Homebrew 23cm Bi-Quad antenna – working VK2FLR at 272 km north-east

Extract of VK1AD SOTA Activator Log: 19 January 2019 – Mt Coree

Six unique QSOs on 1296 MHz and 2.4 GHz and seven QSOs on 144 MHz

Summit to Summit QSOs: Jim VK1AT Mt Stromlo VK1/AC-043 (QF44MQ)

Best DX long distance QSO on 23cm (1296 MHz) at 2.5 watts using the Bi-Quad antenna was with Mike VK2FLR in Sydney. The over-the-horizon path is 272 km via an A380 aircraft enhancement reflection en route to Sydney. 🙂

Time Call Band Mode Notes
22:19z VK1JA 144MHz SSB QF44NO Jason s59 r59
22:21z VK1MT 144MHz SSB QF44NM Matt s59 r59
22:22z VK1MCW 144MHz SSB QF44NN Bill s59 r59
22:25z VK1AT/P 144MHz SSB Jim s59 r59 S2S VK1/AC-043
22:32z VK1RX 144MHz SSB Al s59 r59
22:35z VK1DSH 144MHz SSB Dale s59 r59
22:38z VK1DSH 1296MHz SSB QF44MS Dale s58 r55
22:39z VK1MT 1296MHz SSB QF44NM Matt s58 r58
22:40z VK1RX 1296MHz SSB QF44NN Al s58 r59
22:41z VK1JA 1296MHz SSB QF44NO Jason s59 r59
22:44z VK1MCW 1296MHz SSB QF44NN Bill s59 r59
22:50z VK1AT/P 2.4GHz SSB QF44MQ Jim s56 r59 S2S VK1/AC-043
22:52z VK1MCW 2.4GHz SSB QF44NN Bill s59 r59
22:53z VK1DSH 2.4GHz SSB QF44MS Dale s51 r54
22:56z VK2YK 146MHz FM Adam s59 r59
23:02z VK1JA 2.4GHz SSB QF44NO Jason s59 r59
23:03z VK1RX 2.4GHz SSB QF44NN Al s58 r59
23:09z VK1KW 2.4GHz SSB QF44MT Rob s58 r55
00:11z VK2FLR 1296MHz SSB QF56OD Mike s55 r51 272 km

Photos: © Copyright 2019 Andrew VK1AD

SOTA – VK1 1.2 and 2.4 GHz from Booroomba Rocks 1382 m ASL

Sunday 1 July 2018 – SOTA activation of Booroomba Rocks 1382 metres (4537 ft) ASL, Namadgi National Park on 23 and 13cm (1296 and 2403 MHz)

To secure four unique callsigns on 23 and 13 cm, one needs to plan ahead by informing interested parties at least 2 days out, well that’s the story in VK1. It’s just as much fun organising chasers as it is hiking up the mountain. 🙂 I’m taking advantage of the well-known VK1 VHF Dx Net group who are on air from 0800h to 0900h local (2200 to 2300 UTC). For me and my plans to activate Booroomba Rocks it means a very early start at the base of Booroomba Rocks in the dark, it’s winter in this region of eastern Australia. The 240 metre vertical ascent over 2.2 km takes about 1 hour, I made the summit by 0730h local with 30 minutes up my sleeve to set up.

Looking south to Booroomba Rocks highest point. That’s my target, time is currently 7 am and the weather is looking good. I have just spent 40 minutes climbing in the dark with a headlamp. The summit is a further 20 minutes away.

Great view of the Moon

Sun just peeking over the horizon – I’m now at 1300 m ASL

At the summit and this is the view north to Canberra which is now under the clouds

90 minutes later

Rock Pools are solid blocks of ice, overnight temperature was minus 5 degrees C

VK1AD SOTA shack at the summit

Equipment carried to the summit

Yaesu FT-817 for 2m and as the IF for SG-LAB 23 and 13 cm transverters.

Extract of VK1AD SOTA Activator Log: 30 June 2018 UTC Booroomba Rocks

UTC Callsign Band Mode Distance (km) Grid Square / Notes
22:28 VK1DSH 2.3GHz SSB 37 QF44MS DALE S59 R59
22:30 VK2COW/P 2.3GHz SSB 63 QF44OX DIMITRI S59 R59
22:32 VK1RX/P 2.3GHz SSB 19 QF44NN AL S58 R57
22:33 VK1KW 2.3GHz SSB 42 QF44MT ROB S59 R59
22:46 VK1KW 1240MHz SSB 42 QF44MT ROB S59 R59
22:47 VK1MT 1240MHz SSB 15 QF44NM MATT S59 R59
22:48 VK1DSH 1240MHz SSB 37 QF44MS DALE S59 R58
22:50 VK1RX/P 1240MHz SSB 19 QF44NN AL S59 R59
23:19 VK1AT/P 1240MHz SSB 28 QF44MQ JIM S59 R59 S2S VK1/AC-040
23:27 VK1MCW/P 1240MHz SSB 15 QF44NM BILL S59 R59 S2S VK1/AC-03

As you can see from my log extract, I qualified with a minimum of four unique callsigns on each band 23 cm (1296 MHz) and 13 cm (2.4 GHz). Furthest contact on 2.4 GHz was with Dimitri VK2COW at 63 km (39.1 miles), signal reports were excellent.

Summit to Summit (S2S) QSOs included Jim VK1AT at Mt Ainslie and Bill VK1MCW at Bullen Range.

4el 2m yagi, SG-Lab 23 cm transverter and an all brass 6el 23 cm yagi

SG-Lab 13cm transverter and a 13 cm Bi-Quad antenna

Photos: © Copyright 2018 Andrew VK1AD

Antenna Project – 2.4 GHz 13cm Bi-Quad for SOTA

I recently purchased a 2.4 GHz transverter from SG-Lab in Sofia, Bulgaria. To get you on air the transverter is shipped with a 2.3 GHz 4el HB9CV PCB yagi which at 2.4 GHz has a VSWR 1.7:1, that’s easy to fix. 🙂

In addition to using the supplied HB9CV PCB yagi, I will construct a 22el yagi (in progress) and the Bi-Quad directional antenna mentioned in this post.

You may recall I’ve had good results on 23cm 1296 MHz with a Bi-Quad antenna, also known as a double-quad antenna, so I hope to repeat similar results on 13cm 2.4 GHz. This post describes how I constructed a 2.4 GHz Bi-Quad directional antenna. The VK 2.4 GHz narrow band SSB call frequency is 2403.150 MHz.

13cm Bi-Quad Antenna

For dimensions see: Changpuak Bi-Quad online calculator

2.4 GHz Bi-Quad Antenna Dimensions – courtesy of


  • Double-sided copper clad PCB 130 * 85 mm (I had this piece on hand)
  • 50 mm length of semi-rigid 50 ohm RG402 (mini kits)
  • Female SMA socket to RG402 (solder type)
  • 300 mm length of 2 mm copper wire (junk box)
  • 2 * 15.2 mm stand-off insulators. I used 7 mm diameter plastic sprinkler riser tube
  • 2 * Cable ties
  • PCB enamel

Prepare a double-sided copper clad board 130 mm * 85 mm. Drill the center of the board staring with a pilot drill 1.5 mm followed by a 3 mm drill bit. Use a taper ream to finish the hole.

Debur the hole and edges of the board.

Prepare a 1/2 wave length (43 mm) of 50 ohm RG-402 and a female SMA. RG-402 has a velocity factor of 69.5%.

Assemble connector to RG402 feedline

Prepare the Bi-Quad driven element, 30 mm per side.

2.4 GHz Bi-Quad antenna parts – reflector, RG402 feedline and driven element

Assemble driven element and feedline

preparation for soldering driven element to RG402 feedline

preparation for soldering the driven element to RG402 feedline

Center of the driven element is soldered to the RG402 inner conductor. The two open ends are soldered to the RG402 copper shield

Bi-Quad driven element held in place for soldering

Almost finished – adjust the spacing between the reflector and driven element for a 1:1 VSWR. In this case to achieve a 1:1 VSWR the spacing is 15.2 mm, a small variation (0.4 mm) to the calculator dimensions table.

2.4 GHz Bi-Quad Antenna

2.4 GHz Bi-Quad Directional Antenna

Spacers – 15.2 mm length of 7 mm plastic riser tube, measured with a vernier caliper. Solder the RG402 shield to the PCB front and rear.

RG402 passes through the reflector. Spacing is 15.2 mm

Assembly finished, 9dB gain Bi-Quad antenna

Rear of the reflector – RG402 feedline and female SMA connector

Enjoy building your own 2.4 GHz Bi-Quad. 🙂

To finish off, below is a picture of the supplied 2.3 GHz 4el HB9CV Yagi. This antenna is designed for 2.3 GHz, at 2.403 GHz the VSWR is 1.7:1. To change the antenna’s resonant frequency to the VK SSB call frequency (2403 MHz) I trimmed 2 mm off each side of the two active elements (copper tracks). I left the director elements untouched.

2.3 GHz 4el HB9CV Yagi


2mm trimmed from each side of the active elements.

First published: 19 February 2018
Last Update: 25 February 2018