BATC Forum

I've been working on this on and off as the weather permits. Its a 5 element LFA yagi for 70-71MHz. As described here:https://www.g0ksc.co.uk/70mhz-lfa-yagis ... m-lfa.html and chosen as the boom will just fit inside my radio truck (camper).
I built it exactly as per the published dimensions and the first pic shows the match - optimised for the DX end of 70. Justin (LFA boss) suggested slight shortening of the parasitic elements which I do today, second photo shows the end result. Best of both worlds?? Quoted gain 11dBi so I won't need my 300 watt amp for a while
Last pic shows it up in the air. 3-D printed 'knurled' captive nuts means that only an allen key is needed for on-site assembly.
Next project - 4 element for 6m, also on a boom that will fit inside the R/T-camper Also of possible interest is a tri-band MOXON (6,4 and 2) based on a design in SPRAT 2018 (autumn) which uses coaxial traps and might be handy for scanning around. I've built it from overflow tubing and glassfibre electricians rods (4mm diameter) for flat-packing. Various bits of 3-D printed bits help with holding it all together.

Gareth, G4XAT

That looks interesting Gareth. It would be worth adding a link to this post at https://wiki.batc.org.uk/71_MHz#Antennas

I made the 4m cubical quad seen in Radcom earlier this year. The support tubes are 25mm conduit using intersection boxes. I recalulated for 71 MHz. The telescopic diagonal tubes are worth the extra effort because the square of wire cut to the calculated length doesn't account for bridging the tube diameters at each corner. And you can take up the slack. I recycled the boom and pole from our former TV aerial. After much phaffing about I found a narrow bandwidth low VSWR match at 71MHz.

I hope we're allowed out on Easter weekend for ATV activity days.

Stay safe and well

David M0YDH

Its good to experiment MMANA-GAL (now that I've found I can enter the wires in a GUI of sorts) is great for testing out stuff. I've also completed a full-wave dipole for 2m (talkback) that's better than a 7/8th mounted above it, and an interesting this called a zig-zag. This delivers nearly all-round gain (6dBd) and although vertically mounted is horizontally polarized.
Pics attached. The zig-zag really needs shorter elements which I'm giving thought to. The electricians rods made for easy assembly as the ends are threaded and did the 90 degree joins nice and simple. Just a shade too long with insulated wire, might try with ECC instead.
This is the zig-zag 'thing'..... And this shows the 7/8th above the full-wave, full wave gave 2 S points UP on GB3VHF compared to the 7/8 (both vertical polarization and beacon horizontal AFAIK)
Plot of the full-wave.... My favorite TX spot is by private arrangement so I should be able to 'go out'. Subject to farmer being happy with it.

FIngers crossed

Gareth