Construction of a QRP 23cm HB9CV antenna

Homebrew 23cm (1296 MHz) HB9CV yagi antenna for SOTA

To get the 23cm amateur started, SG-Lab’s 23cm 1296 MHz transverter is supplied with a PCB 23cm 2el HB9CV antenna.    I am very happy with the performance of the PCB version, having worked Rod VK2TWR in Nimmitabel from Mt Taylor in Canberra, that’s a 130 km path with just 2.5 watts.  I have seen 2m and 6m versions of the HB9CV antenna so I was keen to make my own 23cm version using brass for the boom and radiating elements.  Inspiration for this project can be traced to Ernest PA3HCM for his post on a 23cm HB9CV used to access a 23cm amateur television (ATV) repeater.

This is my take on the 23cm HB9CV 2el yagi:

Materials:

  • 2 * 3 mm dia brass rod 120 mm long
  • 6 mm square brass bar 300 mm
  • Piston trimmer capacitor 3.5 pf
  • short length of 1.5 mm copper wire
  • SMA elbow panel to PCB mount
  • solder

For dimensions see: Changpuak HB9CV online calculator

23cm HB9CV dimensions courtesy of changpuak.ch

Prepare two elements as per the dimensions above.  Next mark out the boom element spacings, drill two 1.5 mm pilot holes followed with a 3 mm drill bit. Next chamfer each hole then place the elements into the boom.  Take care to center each element then solder the elements in place.

Reflector and D1 elements soldered in place (both elements are driven)

Other components

gamma match and feed point components

Gamma match

gamma match connecting the reflector and D1

position the gamma match ready for soldering

gamma match soldered in place

Piston trimmer capacitor range – 0.42 to 3.82 pf

piston trimmer minimum reading (pf)

piston trimmer maximum reading (pf)

Piston trimmer is soldered to the gamma bar corner nearest to the reflector (longest element)

piston trimmer capacitor

HB9CV gamma match complete

SMA connector

place the SMA connector center pin to align with the trimmer capacitor pin

Solder the SMA connector to the boom.

SMA connector soldered to the boom

Cut the brass boom 5 mm behind the SMA connector.  Retain the brass bar for the next homebrew antenna.

remove excess boom material

Adjust the piston trimmer capacitor for a low VSWR reading.

Cleaned up 23cm HB9CV antenna ready for mounting in a plastic project box 120 x 75 x 50 mm.

23cm HB9CV yagi antenna finished

Next antenna construction project is a 23cm Bi-Quad   šŸ˜‰

Thanks for reading this post. Good luck with your antenna construction  šŸ™‚

Photos and drawings: Ā© Copyright 2017 Andrew VK1AD

Published: 12 November 2017
Last Update: 12 November 2017

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5 thoughts on “Construction of a QRP 23cm HB9CV antenna

  1. Very nicely done Andrew. A work of art! Not a lot of wind load should you decide to build an array of 2 over 2 over 2. : )

    I had never seen a piston variable cap either. Perfect for your application. Iā€™m going to have to find some for my junk box.

    73,

    Tim
    KA9EAK

    • Thank Tim for the feedback. I’m having loads of fun with small antenna components for 23cm. Working at 0.5 to 1 mm or 1/32 to 1/64 of an inch takes a fair amount of concentration. The measurements at 23cm are less forgiving than say at 40m where a foot or a few inches on a wire dipole makes little difference. I’m enjoying reading your blog, it’s interesting to read your preparation for winter. Cheers Andrew VK1AD

  2. Excellent job on this as 23cm gains momentum for SOTA. I have never seen a Piston vari cap before so I learned a few things today. Thanks

  3. andrew loving your work follow your progress with great interest not able to get out and about like i used to but enjoy catching your feeds please keep them going

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