I've heard of Dave. Funny you should mention Leconfield. I'm ex-REME, a little after you by the sounds of it, and was a vehicle mechanic/auto electrician in Hangar 2 workshops would be around 1992-93.
Yes a beam is the same as a yagi, just another way of referring to it. As I said, the Moxon don't buy one home brew one. All you need to do is to get some PVC tubing, a couple of joiner pieces and two T pieces from B&Q. Make them into a H with each long leg being 3.71m long and the bar between them 1.44m. That'll support the wire. Depending on how ghetto you want to be get a dipole centre too, one of these puppies. If you're not fussy about how it looks you can just solder the driven elements directly to the coax centre and braid.
So this is what we're going to be building.
THESE MEASUREMENTS ARE ALL FOR BARE WIRE. If using insulated wire reduce the lengths by around 5%.
So the reflector you need to cut a length of wire 5.269m plus say another 10cm to allow for tuning.
The driven elements you need two lengths 2.42m. You'll also want a couple of lengths of string say 15cm long to use for "C".
Make up your "H" with the PVC.
Attach the dipole centre to the middle of one of the long legs.
Attach one of the 2.42m driven elements to each side and secure to that leg.
At the far end of each of those driven elements loop a small amount of the cable back on itself and secure loosly with a cable tie just tight enough so it grips but you can still slide the cable through if you tug it.
Attach the reflector element to the other long leg. Again loop a short bit of the cable back on itself, about an inch or so and again secure with a cable tie.
Use the string through the loops on the ends of each side of the driven elements and its corresponding end of the reflector element and tie it so it's tight enough that when you lift the antenna
the unsupported wire doesn't droop. The space between the folded back ends should be about 9cm.
Congratulations you've just built a Moxon beam.
To attach the coax you'll need it to come out at right angles to the driven element for a couple of feet so just tape it to the 4ft bar that connects the two long legs.
If it needs tuning (don't bother if it's below 1.6:1) then just undo a little of the loop on the driven element if the SWR is higher on Ch1 than 40, fold back a little more if Ch40 is higher than Ch1. Once done then tighten up the cable ties and re-tension the string.
The direction the antenna
will be listening and transmitting is in line with the 4ft bar in the direction of the dipole centre so broadside to the driven element.