An 11dBi 2m Quad Beam for £8

There's nothing like a British summer to get hams out in the open, building antennas.  It's been so damp and dull this year, when a nice day comes along, you get through a week's worth of work in a few hours!

So, having completed the very successful vertical dipole, I built a small 2m quad with 2 elements.  The boom and supports were all made with bits of pressure-treated wood going free down the local woodyard.

Looking good in a summer sky: the 2-element 2m quad.  Good for at least 40 miles simplex on 2W.  All the wood was waste from a local woodyard, and free!

This worked really well, and got out to 40 miles simplex quite readily.  It also had reasonable F/B figures, whilst not being so directional that you became isolated from very local nets.

But it wasn't good enough, with just 2W from my handie, to get across the Irish Sea from Anglesey, as I couldn't get into a /M station up on a hill above Belfast one night.  Cue: make a bigger quad!

A really good 5-element quad for 2m is to be found (with dimensions that work!) in the ARRL/RSGB book 'International Antenna Collection'.  The author built in wood, which is a good choice if you want to make cheap antennas quickly.  Wood for internal use is fine, and will last many years, so long as you get it made into an antenna and varnished-up quickly.

It's got a long nose because I hadn't enough wood to add the final director element!  It still managed nearly 100 miles simplex on just 2W.  Total cost: £8 (wire was junk).

I Just offset the narrow support crosses for the wire on the sides of the boom, rather than drill holes for dowels as is done in the book version.  I also didn't cut notches for the wire, preferring just to use time-served cable ties to secure the wire.

Does it work?  Well, I hadn't bought quite enough wood to finish the project, but with four elements on the boom, I stuck it in the air at about 3m on a temporary pole.  It should have a gain of about 9dBi (11dBi when completed!), magically turning 2W into 9.5W (15.4W when complete).

I could hear some weak signals towards Belfast, but the accent of the operators wasn't right; I turned the antenna south of the border to find the signals were in fact coming from Co. Wexford, with EI9GGB in QSO with EI9GLB.  I made a break call - using just 2W - and was heard straight away by GGB.  I was 56-7 to him, 44 to GLB.

94 miles simplex on 2W from a £34 handie into an £8, unfinished antenna.  That's my kind of amateur radio!

A few days later, I broke the 100 mile barrier with a 56 into G8XVJ/P above Leek in Staffordshire, working an RSGB contest.  I had to wait until the worst of the 59+s around him were finished, but come on - it's just 2W from 101 miles away!  I also managed to open the GB3CP repeater in Co. Fermanagh, and even managed a QSO with GI4UHP/M, though my signal was not very strong.  Not surprising, at 150 miles!

Now with the final director added, we should be at 11dBi gain.  Time for a proper mast, too!

Mind you, I have to admit I am tempted very much by the nice-looking, lightweight 8-element 'Scorpion II' quad for 2m as sold by Cubex.  That's a very good price for an antenna of such gain (~14dB, turning 2W into an astounding 30W), so long as the UK import duty bureaucrats don't get hold of it on the way!

UPDATE:

A word about  feeding.  Most 'advice' online tells you that a 1/4 wave matching stub is necessary to bring a good match on this antenna.

This is not true!

To prove it, here's the result with the 1/4 wave stub in place, as shown on my recently OSL-calibrated SARK-110 analyser:

A 1/4 wave stub yields 100 Ohms impedance, and a high SWR.

Rather obviously, this is the wrong impedance and a fairly high, though entirely usable, 1:8 SWR.

Dispensing with the stub altogether, connecting directly to 50 Ohm coax, the SARK now yields this ideal result:

That's better!  Good impedance, and a <1.3:1 SWR.

 So there you have it!  For this multi-element quad, a direct 50 Ohm coax feed is the correct arrangement.