There seemed to be a bit of interest in the design when I posted photos on the reflector. However, some comments emailed to me said it didn’t look very solid or very well built. My previous attempt was a simple test. I’m now please I’ve built a version I’m going to use for SOTA and the 2m Backpackers:
I was checking out GB3NGI beacon in Northern Ireland, which came through as a just audible on the QQ and I couldn’t hear it at all on 7 element tonna so this is good news. Bear in mind that direction from my home QTH is going through the hill next door too!
The attributes appear to be as promised, I could make out the beacon through at least 60 degrees of rotation.
Thought I’d post in-case anyone is interested in a follow up…
Having used a version of the antenna on 23cms in the past, I have experienced the excellent performance that this antenna can give. My only concern about using a 2m version for SOTA would be how to break it down to carry it to the summit and how long it would take to assemble once you are there. Of course for the backpackers contest that is not an issue as you won’t be doing more than one summit in the day and the time required for unpacking and assembly, together with perhaps a slower ascent on account of the weight of the antenna can all be accounted for.
I’m pretty sure I saw your version on Flickr? I think that’s where it was. It looked very cool!
This is a bit of a beast. Every joint has been crushed in a vice and then drilled. A small bolt then goes through each joint to put it all together. This means the whole thing comes apart and can be latched together like a bunch of ‘sticks’ for carrying.
That makes 20 bolts at the joints. There are additional bolts (nylon) at the mounts and stuff. I’m hoping I can go round with a quick ratchet spanner and chuck it all together. Certainly not something for a 5 summit day out though!
My first version of this antenna involved wire and relied on the whole thing being under tension (like the 70cm version on Roger’s website, MW0IDX). But for the up-scaled size of the 2m version I was displeased with the structural strength and the tolerances seemed very low, the antenna often “sitting” as it pleased, slightly askew in all three planes. This may be down to my lack of accuracy when constructing the antenna though - some parts of the original design are absolutely critical.
This new version would withstand a hurricane - but at the cost of convenience.
Thanks for your wishes for the contests - I’ll keep you up to date as to progress. My feeling is that I won’t do very well and I’m just going into it for the fun - so anywhere up the league table will be a bonus.
When we were having SOTA Activity Days, I did wonder whether to make a 2m version out of copper micro-bore pipe with right angled and tee joints for use on a single summit. However things have moved on - the Activity Days have died a death and the summits that I am now interested in are too far away.
In construction terms, the main problem with my idea was that the only pipe that I could find was soft-drawn and came on a roll. Using the hard-drawn 15mm pipe would have been far too heavy. Even with your construction method, I don’t envy you the ascents you have planned… maybe you will be granted membership to the YYY Heavyload Activators Club.
It’s all good stuff Rob. It will be interesting to see how it works on 2m Backpackers where you should have plenty of horizontally polarised takers.
Interesting you couldn’t hear the beacon on a 7 ele Yagi. Theory states it should have the same gain as 5/6ele Yagi. Reports suggest this type of antenna will work better than a Yagi when mounted lower which is good for portable setups. The broad horizontal pattern should minimise beam twiddling too. But as we know the difference between theory and practice… yada, yada, yada.
If there are “a few” bolts to do up then can I suggest now you have plenty of spares with you. You’d be so annoyed if you dropped a nut or two into the heather and couldn’t assemble it after the effort put into construction. Also wing nuts maybe better than normal nuts. We have an M2 13lambda Yagi for 70cms contesting that is 9m long with a boom that splits into 6 sections. That means 5 joints to assemble each with 2x 50mm M4 bolts and wingnuts. It takes a silly amount of time to do them up especially once your fingers get a bit cold. It’s easy to drop the bits into the grass on our contest site and they’re gone for good then.
