a homebrew hf quad antenna for 14 mhz - vvarc.net

A Homebrew HF Quad Antenna for 14MHz

By Dave, M0TAZ – [email protected]

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The objective was to build a simple 2 element quad that I could use portable or on contests away from home. The antenna needed to be portable, cheap, light and easy to construct on the day of use. I needed to be able to pack the antenna down and transport to site by car.

Firstly lets deal with the questions why a quad, this is simply down to dimensions and performance. I have used a Quad antenna on 144 MHz in the past, and always been very happy with the gain v boom length. They may be a little more complicated to construct, but the performance has always compensated. I also noticed that Quad antennas seem to have fallen out of fashion, with very few commercial built antennas available today.

The basic calculations I had made suggested the spreader arms needed to be at least 4m long. To meet my portable objectives the quad needed to fold down when not in use, so I decided to use lightweight 4m fishing poles as the spreaders. A quick look on an Internet auction site soon secured 8 x roach poles from a fishing supplier.

Once I received the roach poles I ordered some exhaust clamps that would fit over the base of the roach pole, and mount these to the Perspex plate. In my case 25mm Exhaust clamps was ideal, and I needed 2 for each pole (16 clamps in total)

The roach poles needed to connect to a plate, and for my proof of concept I decided to use a Perspex plate, 4mm thick 300mm x 210mm was readily available online. I also looked at various brackets; I wanted something that would connect the boom to the Perspex plate.

Once again the Internet offered various brackets, I decided to use a TV Aerial Pole bracket.

These could be purchased, and with a little modification I was happy these could be pressed into service.

Stage one was to find a nice open space to test the basic construction. I drilled out the Perspex sheet which was not without its problems, as Perspex is rather brittle and one of the sheets fractured towards the end of the drilling. I had ordered spare sheets, and I found various methods helped, such as a pilot hole followed by the correct size drill. I also noted you can purchase drills specifically for drilling plastic, but as this was not something I tried.



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Perspex drilled and centre brackets mounted -‐ Roach poles mounted

Roach poles retracted -‐ Fully extended with antenna wire.

I calculated that the reflector would be 3.97m per pole, and the driven element would be 3.77m. The antenna wire (standard bell / speaker wire) would then simply form a square around the roach pole, with its size dictated by the square formed by the poles. The calcualtions suggested with would need 22.5m of wire of the reflector and 21.3m for the driven element. The boom length would be around 3.4 meters.

In the first instance, I used simple swaged poles to test the construction. The antenna was fed with 50 Ohm coax for the test, and this provided a close match to 14.2 Mhz. I read the boom length can be much longer, sometimes 4.5 meters but this was not an option for my car friendly version.

The basic antenna construction worked, for testing the antenna was little more than 5 metes above the ground. The antenna had some gain, and when orientated to the side of a station in most instances they would disappear into the noise. The gain on the back was less than the gain on the front, so at this stage I was happy to call the proof of concept a success.



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Stage 2 was finding some more robust centre plates and boom that could still meet the portable objectives. I decided to use Aluminium plate 5mm 210 x 210 mm and a boom that was Aluminium round tube 25mm 10 SWG x 5 meters.

I could then re-‐use all the previous brackets and clamps to form a more robust solution.

Centre plate with boom mounted -‐ Centre plate with roach poles mounted

Having re-‐assembled with the new centre plates the quad is much more rigid, although I think alternative poles may be required for a semi-‐permanent installation. The roach poles are built for a price, and I would expect degrade with exposure to UV for any prolonged time.

Antenna testing



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Antenna feed: The coax feeds the driven element in the centre bottom of the loop, and this needs some strain relief. This can be achieved by dropping a length of fishing wire from the boom to the coax connection join, and transferring any weight onto the boom.

I noticed my match was close to 50 Ohms, but much will depend on your boom length and wire dimensions. The antenna also provided a handy match on 28 MHz, not sure how efficient but I did manage to work a W6 and W7 west coast!

Limited testing showed it out preformed another hams 3e beam and on side by side testing, the S/N ratio was noticeably better on the Quad.

Inventory and cost

£40 – 8x 4m roach poles

£8 – 2x plate 5mm 210x 210 mm

£15 – 2x centre boom support brackets

£6 -‐ 25mm Exhaust clamps

£16 – 25mm 10 SWG tube 5 meters

£12 – 100m speaker wire.

Total cost £97.

a homebrew hf quad antenna for 14 mhz - vvarc.net

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