A Lightweight 4 Element Delta Loop for 11m
Here’s a nice project to build a 4 element Delta loop for the 11m band. It’s super lightweight and very compact, using a boom length of only 5m. The criteria was to design an antenna that could potentially be used as a very high performance portable unit. Being on a standard boom length of 5m [Most aluminium lengths are 5m as a default from the mill] means the boom can be retained as a single section without cutting if desired.
As an option, it could also be used in a fixed location. However, the design is not optimised for high-wind areas and the 1.5 inch 10 gauge boom is pretty well ‘maxed out‘ at 5m so we’d advise against a permanent installation unless your QTH is kind to you with the weather. You [could] though fit a small boom-end guy to prevent or at least reduce the amount of sag, or potentially install a slightly larger cross section boom.
When it’s ‘homebrew‘ there’s no right or wrong – it tends to be what’s available!
This was one design that does not use our ‘top-wire‘ support like seen in other designs. As the requirement was for an antenna was was predominantly portable, we used single sections of ‘Flexweave‘ for all 4 elements.
All Elements – Top Wires:
We used a 14 AWG ‘Flexweave‘ style of stranded copper wire for all the elements which is PVC coated. The total diameter including the PVC is about 4mm. It’s very strong but easily handles QRO. Using this wire for the ‘Driven Element’ is ideal as it is very capable of 2kw+. Using bare wire is not recommended as the velocity factor of the wire is different. The PVC coating changes the v/f of the wire and as such, the lengths shown here will not be correct.
Note: – there is NO top wire support. Each wire has a single copper tube terminal on each end soldered to the Flexweave. This makes for easy installation.
Fancy a crack at building this baby? – Here’s the data you need below
You [may] not require a gamma match. Try it out first and see what your SWR bandwidth and curve is. If you do need one, then here’s your data.
Here’s an update to the driven element. Instead of using a ‘threaded’ 3/8th inch stud to mount the gamma match, we use an M8 bolt which is mounted to a separate nylon mounting section. The bolt sits in a 12.5mm PTFE insert so handles very high power as ‘QRO’ can melt nylon. A small length of ‘Flexweave‘ then goes back to the rear of the SO239 socket.
I found a good supplier of quality SO239 sockets which has PTFE insulation. Check out Barenco’s site here. This enables us to use an external higher quality SO239 [or any other good quality coax socket].
The M6 socket [Allen] cap head bolt with the yellow soldered crimp connector is the earth and is connected to boom/chassis earth. This subsequently links to main element tube. This gives a great result all-round.