Home > Uncategorized > Making Waves – A DIY HF Antenna for the smallest spaces

Making Waves – A DIY HF Antenna for the smallest spaces

Is your garden the size of a postage stamp? Or maybe you live in a flat/apartment with just a balcony, then this could be the antenna for you to get on the air using HF frequencies. We all know that an HF dipole for 40m (7MHz) is going to be 20m (66ft) in length and not everyone has the available space to fit one in (hell, a 1/4 wave vertical is going to be 10m (33ft) long and may require planning from your local authority. So how about a vertical antenna that is only 1.7m in length and covers all HF amateur radio frequencies from 7MHz to 28MHz via your ATU? Impossible I hear you say, not at all – read on to see how it is done….

What will you need? Not much really, you will need a length of plastic pipe, 1.70m long, 41mm in diameter – this is sold in the local hardware stores as 40mm waste pipe but be careful, 40mm is the inside diameter and it is available in either 41mm or 43mm outside diameter – 13.6m of 1.5mm insulated copper wire, some 20mm long cable ties (200 * 3.6) and a 4:1 UNUN (see later for instructions).

Effectively, take One end of your wire and secure it to one end of the 1.7m pipe using one of the cable ties. Wind on 67 turns of the wire over a length of 220mm and secure with a cable tie (insulating tape can also be used). Now drop the wire vertically for a length of 360mm and secure again. Wind on 22 turns (in the same direction as previously) over a length of 70mm and secure again. Then wind three turns, wide spaced over 820mm (and secure again leaving the end free. This end then needs attaching to your 4:1 UNUN.

For the 4:1 UNUN you can either build your own by following the image below:

Or buy one ready made (Magituner A) from www.m0cvoantennas.com .

Leave a short amount of space at the bottom of the pipe to fix either a bracket (if you are going to pole mount it) or use cable ties to fix it to railings on your balcony, etc. You will need to attach an earth wire to the second peg/machine screw. This only needs to be short – maybe 4 or five foot but does help with the matching. Attach coax to the SO239 socket using a PL259 plug and run back to your radio via an ATU (the internal one (if fitted) may be able to cope with this) tune up and away you go.

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