Antenna Project – HF QRP End Fed Half Wave

Homebrew HF EFHW antenna for low power SOTA, Parks and field day events. Using a 19.8 metre length of wire mounted as an inverted V, a non-resonant 6.8 metre counterpoise, this antenna is resonant in the 40/20/15/10m bands. At 19.8 metres long, the VSWR is less than 1.5:1 in the voice segments. If your primary operating mode is CW, you may wish to consider changing the length of the radiator. Note an antenna tuner (ATU) is not required for operation in 40/20/15/10m bands.

Materials:

  • Winder/Insulator: 3 mm kitchen cutting board, purchased from a mainstream supermarket (hint, down down)
  • Toroid: FT140-43 from Mini Kits S.A.
  • Capacitor: 100pf silver mica rated at 500v
  • Length of enamelled copper wire (select the appropriate wire size for your maximum operating power)
  • 2 x S-clips
  • 27m 22 AWG insulated copper wire. Select the appropriate wire for your operating power.
  • BNC socket or an RF socket of your preferred choice
  • 2 x crimp auto spade connectors
  • 2 x small cable ties
  • 2 x M4 20 mm stainless steel round head, hex screws
  • 4 x M4 washers stainless steel
  • 2 x M4 washers large
  • 2 x M4 wing nuts
  • 2 x M4 stainless steel nuts
  • 2 x solder tabs
  • 2 lengths of 2 mm hoochie cord
  • Fabricate an end insulator: Use an old plastic coat hanger or use a section of the kitchen cutting board

49:1 Impedance Transformer – 2 turn Primary and 14 turn Secondary. Twist together the first two turns of the primary and secondary windings.

Cut a section of 3mm kitchen cutting board 165 mm x 100 mm. The two winding cut outs are 25 mm deep by 63 mm wide.

Drill 4 anchor holes with a stepped drill bit.

Secure the 49:1 toroid in place with two opposing cable ties

The BNC connector ground tab and the counterpoise wire tab are soldered together to form a common ground.

49:1 Impednace Transformer
49:1 Impedance Transformer circuit diagram
Insulator/winder is 3 mm kitchen cutting board purchased from a local supermarket
FT140-43 49:1 Impedance Transformer
Homebrew EFHW 49:1 Impedance Transformer for 40/20/15/10m bands using a FT140-43 toroid and 100 pf silver mica capacitor.
Antenna tie off using a S-clip. Radiator is a 19.8 meter length of plastic insulated 22 AWG copper wire.
Feedpoint – BNC socket and the anchor tie off using a S-clip, bottom right. Counterpoise wire bottom left.
Portable homebrew EFHW Antenna assembly
Portable homebrew EFHW Antenna assembly – Rear view
Portable EFHW Antenna
Homebrew inverted V portable EFHW antenna supported by a 7m telescopic pole – SOTA activation using 40m and 20m bands.

Extract of VK1AD SOTA Activator Log – Mt Cowangerong 28 February 2021. Radio FT817ND output power set at 5 watts.

VK1AD Mt Cowangerong 20210228
28 Feb 21 VK1AD QSOs from Mt Cowangerong – Image courtesy of SOTA Maps
TimeCallsignBandModeNotes
00:03VK5IS14MHzSSBIan s59 r57
00:04VK1MA14MHzSSBMatt s59 r43
00:05ZL3QR14MHzSSBs55 r55
00:06VK1MIC14MHzSSBWade s51 r55
00:08VK4CZ14MHzSSBScott s59 r56
00:10VK4BXX14MHzSSBs59 r54
00:14VK5PAS14MHzSSBPaul s59 r57
00:18ZL2ATH/P14MHzSSBWynne s56 r58 S2S ZL1/WL-138
00:20VK4KC14MHzSSBMarty s59 r54
00:20VK3PF14MHzSSBPeter s55 r42
00:22VK4SYD14MHzSSBRob s59 r57
00:24VK4NH14MHzSSBs59 r55
00:28VK3KAI7MHzSSBPeter s59 r58
00:28VK2IO7MHzSSBGerard s59 r45
00:30VK4EKA7MHzSSBDougal s58 r51
00:41VK1MIC144MHzFMWade s51 r51
VK1AD SOTA Activator Log – Mt Cowangerong

Standby for an update in the next week. I will update this post with VSWR plots.

VSWR plot – 7 MHz to 28 Mhz

Last Update: 11April 2021

3 thoughts on “Antenna Project – HF QRP End Fed Half Wave

    • Hi Andrew after a very long Hiatus of nearly 6 years I will be doing my First activation late this week or early next depending on weather VK3/VG-021Mt Tingaringy My brother hasn’t been up there I last activated it in 2016 Looking forward to and activation Cheers 73 Rod VK2TWR

      Sent from Mail for Windows 10

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