Meschore Continues

It's been a busy few weeks, including getting to grips with Meshcore and its various elements.

Luckily, there's a repeater within line-of-sight - just - of me and this helps develop the interest. Slowly, more repeaters are appearing across Anglesey and, come summer, this may well pick up significantly.

Attention in the past couple of weeks has turned to antennas. At home, a window-placed test 8.5dBi collinear from Paradar has proved to work perfectly well, although it doesn't really offer any advantage over what the stock stubby antenna was delivering. Not really planning to stay at this property much longer, I've resisted putting this antenna outside and stuck it in the loft instead. It does OK there.

With one unit tied up in the loft, I decided to buy a Heltec V3 with GPS and a 3-D printed case, so that I could shove it in a rucksack and take up the mountains - or just a hill overlooking the Irish Sea on Anglesey. The weather being so wet, though, I haven't managed to get out to do this!

Instead, I've been testing the handheld unit out on my daily walk around the local reservoir, which is surrounded by a relatively narrow strip of conifer trees, which of course have pretty dense branches and needles - very effective and blocking microwaves!

 

The only place I could get a signal from the handheld's stubby antenna to my home was from an old railway embankment across a lake that has a relatively clear line-of-sight path (orange and turquoise positions, both at ~2km). From any position on the dam, which has a path through 250m of conifers and also lies behind a low hill on which they grow (pink and white positions), I couldn't get a signal back home with the stubby. 

Line-of-sight (terrain) map for the dam. LoS is only in the clear areas, free of dark lines (the upper end of the lake isn't correct, because it fails to properly take into account the effect of the trees).

 

I felt I could do better than this, despite the very low power involved (22dBm, or 160mW). 

So I built a simple 1/4 wave vertical with four sloping radials, based on a N-type panel mount socket with a SMA connector on the other side. I simply soldered the radiator into the centre of the N-type and attached the radials to the panel mount holes. With a bit of trimming, I got a nice matching curve with about 1.25:1 SWR. I fixed the whole thing to a timber stick using a 15mm PVC pipe clip, into which the N-type screw thread mount fits snugly.

The Heltec v3 attached to its stick-mounted vertical.

 

So, looking more of a nerd than ever, off I went for a walk with the handheld, but now connected to the new vertical antenna. I was only going to send one test 'advert' signal from the most challenging position - the nearest point on the dam, at 1.8km exactly and through all those trees and a low hill. Would it get through?

Satisfyingly, it very much did! It's no surprise to anyone who has used stock stubby antennas that they are very poor and something to be discarded as soon as possible. And so it is at 868MHz. 

Success! Signal heard back home from the dam.

 

Of course, a PVC tube collinear is more convenient and robust to carry around that a spidery vertical for mountain hiking, for example. But it's also not an impossible antenna to carry in your hand or sticking up from the backback.

Very satisfying experiment, costing no more than the price of a N-type-to-SMA panel mount connector.

Incidentally, at the moment, you can save yourself well over £20 if you buy the same ~6dBi collinear from McGill Microwave Systems rather than the popular Paradar outlet.