Monday, 24 October 2016

Ultimate 3S Beacon - Almost Complete

As well as charging batteries, and reading more Mark Twain, ive also done a little more work on the Ultimate 3S today,

Having built the main unit, the synthesiser, and most of the GPS unit, I pondered slowly along today with the Low Pass Filters. One small thing I noticed, which I may mention to Hans for a possible future improvement, is that there is no easy way to see what band a filter is built for! The underside of the PCB is all groundplane, and so I have marked the band on mine using a Sharpie pen, but from the component side theres no place to mark. Im not sure what the solution would be, perhaps an extra 1 or 2mm along the side of the board to give a writing space? or perhaps scratch boxes on the silkscreen for each band to mark?

Anyway, the first job way to fit the capacitors. These filters use a tried and tested design detailed on the G-QRP club website and in SPRAT, being 7-pole filters.

Some way of holding the tiny PCB steady is essential! Below is the 10m LPF having its capacitors soldered in place.

One problem with this build, which is fully appreciated and warned about by Hans in the paperwork, is getting the header pins aligned properly! My solution to this problem is to slip the pins into a piece of Veroboard prior to soldering

A bit of Veroboard helps align the header pins when soldering
After this came the task of winding the toroids. L2, the middle one, went just fine, 24 turns. But somehow the other two I managed to get the wrong 'handedness' to them - meaning the wires were on the wrong side of the toroid from the holes! Both had to be unwound and done again! And then, on one of them, I managed to get the turns crossed over and knotted!

But, after unwinding as far as the crossed section and rewinding, followed by some hard work getting the damn thing soldered back in, I finally have the 40m filter complete. A bit of hot-melt glue was used to secure the toroids in place.

The above photo shows my 'almost' complete Ultimate 3S Beacon, ready for 40m operation. The last task will be to make up a header plug to connect power, and to connect the RF out to a coax socket. I should have a coax tailed socket of some sort that will work for this. Another header cable, this time 4-way ribbon, will be made up to connect the GPS unit.

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