MØCEP

CADARS

The Mill Public House

236 Station Road

Brimington

Chesterfield

S43 1LT

A Radio Society of Great Britain affiliated club

Windom HF Antenna

David R Moore G8CGZ

Having held a 'B' licenced since 1970 I was only able to operate above 30 Mhz and had explored most modes on 144 Mhz (2m) and 432Mhz(70cm) with Rx only on 1300 Mhz (23cm) TV. After the granting of a full licence to all 'B' licence holders I purchased my first HF Transceiver in March 2008.

I soon found that the antennas I had been installing like TV antennas on the chimney were to change to wire contruction that took up ALL of my garden! This is the story of my contruction of a Windom HF antenna which I hope will help others be up and running on HF with a cheap and efficient antenna.

First was the shopping list :

Antenna Wire - Plastic covered multistrand

Insulators - Plastic ribbed

Balun - 4:1 with SO239 socket

Feeder cable - 112ft (34m) of RG58

Plugs - PL259

Mast - 20ft (6m) 2" aluminium

10ft (3m) 1.5" aluminium

Mast Clamps - various to suit 2" mast

Nylon guy rope.

The basic layout is shown on the diagram below:

The antenna wire should be cut to the following lengths allowing approximately an extra 18" for connecting and tuning adjustments later:-

2/3 wire 88ft (26.83m).

1/3 wire 44ft (13.41m).

The balun should have the antenna wire anchored and soldered as shown on the diagram below :-

Band

Freq.

SWR 1

SWR 2

80m

3.600

1.10

40m

7.060

1.05

30m

10.140

2.60

1.05

20m

14.200

1.10

17m

18.100

1.40

15m

21.200

2.50

1.60

12m

24.900

1.15

10m

28.200

1.30

10m

29.000

1.60

10m

29.520

1.80

10m

29.700

1.80

The feeder can now be prepared by fitting a PL259 plug at one end only. A choke is now made approx. 18" from the PL259 by winding 21ft of feeder onto a plastic former (drain pipe 40mm dia x 250mm long) and anchoring the ends with PVC tape. A second choke is made by the same method approx. 36" from the other end of the feeder and the PL259 fitted for the transciever . These chokes are to stop RF radiating from the feeder, therefore reducing TVI.

After connecting the feeder to the SO239 socket and water proofing with amalgamating tape the antenna should be erected on a mast or a suitable high point from the supension eye so that the balun and feeder are supported. If an aluminium mast is used the balun and suspension point should be offset from the mast by a short horizontal pole of approx. 18" to reduce the capacity effect with the feed point which might detune the antenna.

The free ends of the antenna wire should be fastened to the Ribbed Insulators and nylon guy ropes to fasten off to a suitable point at least 8ft above the ground. In my case the feed point is mast mounted at 30ft (10m) with the 2/3 wire anchored on the house chimmey at 30ft (10m) and the 1/3 wire anchored onto a washing line post at approx 7ft. The antenna runs north/south with the 2/3 wire to the north.

After the windom was erected it was time to check the SWR and see if all was working OK. The results of the SWR measurements were very good and are tabulated below:-

Below are a series of photos showing various construction aspects:-

SWR 1 - This is with the antenna connected directly to the Transciever.

SWR 2 - This is with the antenna connected via an Autotuner.

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Mast clamps joining 6m to 3m mast

Ribbed insulator and guy rope

Choke and former construction

Insulator with wire and guy fastening

Completed construction on mast at side of shack

Balun and choke showing offset