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. πŸ™‚

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. πŸ™‚

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


5 thoughts on “Antenna Project – 2.4 GHz 13cm Bi-Quad for SOTA

    • Hi Paul, I haven’t modelled the antenna myself. Loads of reference material on the web, believe or not, which conservatively indicates a 7 to 8 dB gain, I wouldn’t claim much higher. In the real world my 23cm Bi-Quad has proven to be a strategic asset, a good lightweight portable solution for SOTA where height above sea level is a contributing factor to the antenna’s overall performance. I am hoping the 13cm version is equally as good as the 23cm version. I hope to have a 20el 13cm DL6WU completed in the next week or so. 😊


  1. Pingback: Construction of a 23cm 1296 MHz Bi-Quad Antenna | Get out of the Radio Shack and Live Life

  2. Pingback: Antenna Project – 2.4 GHz 13cm Yagi for SOTA | VK1 SOTA on 1.2 and 2.4 GHz

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