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 – 2.4 GHz Yagi failed at Mt Tumorrama VK2/SW-027

Sunday 27 May 2018 7:30 am Mt Tumorrama. My homebrew 2.4 GHz Yagi had failed at when I noticed the 2.4 GHz 2.5 watt SG-Lab transverter SWR LED had changed to RED! Hmm.. bugger that wasn’t expected.

I didn’t have time or the tools to repair the antenna so I persisted with my backup antenna a 2.4 GHz Bi-Quad (below). I was pleasantly surprised by the performance of the Bi-Quad by successfully working Al VK1RX/P for two SOTA S2S contacts at VK1/AC-023 and VK2/ST-005, Dimitris VK2COW over a 64 km path and Matt VK1MA/P S2S at Mt McDonald VK1/AC-048 along a 39 km path of multiple 1200 m ASL mountain ranges.

Back to the 2.4 GHz Yagi. Today, using a pair on 2.5 magnification glasses I took a closer look at the folded dipole assembly. This is what I found 😦

2.4 GHz folded dipole assembly

Close up – 2.4 GHz folded dipole assembly – You never know what can go wrong at SOTA summit!

Let’s crack open the soldering iron and fix that bad boy.

Wow a clean break. A stress crack between the SMA center pin and the copper dipole

Earlier photo of the assembled 2.4 GHz Yagi

Balun impedance transformer – 43 mm length of RG402

For info – 2.4 GHz Bi-Quad photo taken earlier in March 2018

March 2018 – 2.4 GHz Bi-Quad photo courtesy of VK1MIC

73, Andrew VK1AD

SOTA – VK1 2.4 GHz S2S Party

Sunday 4 March 2018. VK1 is holding an early morning SOTA 2.4 GHz and 1.2 GHz S2S Party with VK1 microwave activators setting up on five peaks plus Bill VK1FWBK on 2m FM. It’s 7:30 am (20:30 UTC), Wade VK1MIC and I have walked 3 km to set up two stations on the summit of Mount McDonald VK1/AC-048 789 metres ASL, grid square QF44LQ. Wade has deployed a HF + 2m station and I have set up my 1.2 and 2.4 GHz SG-Lab transverters. Liaison with local VK1 stations was planned for 146.500 FM, however due to competing SOTA chaser traffic we thought it best to move to 146.525 FM. For future microwave activations the VK1 group will liaise on 146.525 FM.

So who’s on which SOTA peak?

As mentioned Wade VK1MIC and I have chosen Mount McDonald primarily as the summit is free of trees and vertical obstructions as viewed to the north, east and south. The bulk of my fellow SOTA activators are east of Mt McDonald. I figured Mt McDonald is the best strategic option.

To my east, Bill VK1FWBK was an early riser making the top of Mt Majura with a 2m HT, Matt VK1MA has set up on Mt Stromlo VK1/AC-043, Al VK1RX is ready to go on Black Mountain VK1/AC-042 with a 24el homebrew yagi while Paul VK1ATP is assembling a 2.4 GHz Grid Pack antenna plus a Cantenna on the summit of Mt Ainslie VK1/AC-040. Mt Ainslie is 20 km east of my position at Mt McDonald.

That’s five out of six activators, who else volunteered to get out of bed at 5 am? Andrew VK1DA/2 has opted to set up on his so-called local peak, Mt Mundoonen 10 km north of Yass in the state of NSW and 54 km north of Mount McDonald. Andrew has a hombrew 2.4 GHz transverter plus a SG-Lab 1.2 GHz transverter. I have line-of-sight to Mt Mundoonen, a 2.4 GHz S2S with Andrew should be a formality.

Terrain between AC-048 and ST-053 54 km north

Terrain between AC-048 and ST-053, 54 km north

So how did we go on 2.4 GHz? The group of five in Canberra; Matt, Al, Paul, Wade and myself worked each other with ease, 5-9 signal reports all round. On the other hand working Andrew VK1DA/2 at Mt Mundoonen 54 km north of Mount McDonald became a major challenge for all. Andrew was experiencing 2.4 GHz equipment problems so he set about rectifying the problem. In the meantime the group of five, including Andrew moved to 1.2 GHz, 1296.150 MHz for a second round of S2S contacts. All five summit stations worked each other with ease, 1296 MHz was a pushover.

With 1.2 GHz done and dusted, the group moved back to 2.4 GHz looking for a weak signal from Andrew at Mt Mundoonen. Finally it came, at first a weak distant voice in the noise followed by a sudden lift in signal strength for a readable report at 5-2. On Andrew’s side my SSB signal was 4-1 sufficient to confirm signal reports, exchange summit codes followed by ‘QSL’.

Success! Qualification on 1.2 GHz and 2.4 GHz plus a bonus 2m S2S with Bill VK1FWK. 🙂

Extract of VK1AD SOTA S2S Log: 3 March 2018 (UTC) Mount McDonald

Time (UTC) Station Summit My Summit Band Mode Distance (km)
20:39 VK1FWBK/P Mt Majura Mount McDonald 146MHz FM 23
20:43 VK1RX/P Black Mountain Mount McDonald 2.3GHz SSB 15
21:09 VK1MA/P Mt Stromlo Mount McDonald 2.3GHz SSB 6
21:24 VK1ATP/P Mt Ainslie Mount McDonald 2.3GHz SSB 20
21:34 VK1MA/P Mt Stromlo Mount McDonald 1240MHz SSB 6
21:38 VK1RX/P Black Mountain Mount McDonald 1240MHz SSB 15
21:43 VK1DA/2 Mt Mundoonen Mount McDonald 1240MHz SSB 54
21:50 VK1ATP/P Mt Ainslie Mount McDonald 1240MHz SSB 20
22:23 VK1DA/2 Mt Mundoonen Mount McDonald 2.3GHz SSB 54

Photos: © Copyright 2017 Andrew VK1AD

View east – sunrise from Mt McDonald

View south over Bullen Range and Namadgi National Park.

13cm Bi-Quad is facing east working stations over a short distance (20 km) to Canberra

I’m still considering the Bi-Quad mounting arrangement – for now the 2.4 GHz Bi-Quad is resting on two blocks of wood.

SG-Lab transverter IF frequency 435.150 MHz is derived from the FT817 at 500 mW. Transverter local oscillator frequency (LO) is set to 1968 MHz for 2.5 watts RF output on 2403.150 MHz.

SG-Lab 13cm 2.4 GHz transverter with a 2.4 GHz Bi-Quad resting on two small blocks of wood. Photo courtesy of Wade VK1MIC

Andrew VK1AD in his favourite position – lying in the Aussie dirt on a mountain peak 🙂


Andrew VK1AD SOTA shack. The white pole is a 2m half-wave vertical. Photo courtesy of Wade VK1MIC

23cm Bi-Quad facing north to Mt Mundoonen – signal report exchange with Andrew VK1DA/2 was 5-9


23cm 1.2 GHz Bi-Quad antenna and transverter mounted on a tripod

Post update: photo supplied by Al VK1RX of his 13cm transverter and 2.4 GHz yagi set up on Black Mountain

Photo courtesy of Al VK1RX

First published: 5 March 2018

Last Update: 6 March 2018

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