A couple of months ago, the SOTABeams Facebook page Posted a link to a new item they had just finished making. A simple pair of lightweight dipole traps for portable use to help with running multiple bands and the band changing efforts. I had built a link dipole last year and this works well, but if the mountain you are on is a little bushy or difficult to setup on, the efforts required to change bands with the links on the dipole can be a real effort (at times) maybe I’m just LAZY!..
So I ordered some, they were pretty reasonably priced (around $25aus delivered), and a week or so later arrived in the PO Box. I got the 20w versions as I will be using them for SOTA only. they also sell a 100w version for a little more. They recommend you buy paint on electrical tape (to weather proof them, i didn’t order any, but this can be purchased from Altronics if you are in Australia)
It took me a while to find the time to make them up, but i had a free day (Anzac day i recall) and spent some time making them up.
They are pretty simple to construct, about 15 mins per trap taking my time, just follow the instructions that are on the SotaBeam website as well as the Excel spreadsheet for working out the details Here and choose the Frequency you wish the traps to work at. This corresponds to the amount of winds on the Toroid core and the configuration of the Capacitors. All explained at the website and in the Instructions.
I made my traps to operate on 14Mhz, choose one 100pF capacitor, and 17 turns on the core.
Once I had built up the traps, it was time to test them, the design smartly includes a simple link and some test pads. (those big square pads in the photos on the right hand side of the PCB), you connect your analyser to those pads and measure the frequency response of the traps.
That required me to also build up a simple test lead for my analyser. It was a very DIY afternoon of tinkering.
Once you are happy with the performance, you simple bridge the bottom test pad to the smaller pad adjacent to it and its a trap for your antenna. Now all I need to do is find time to connect them to a real antenna and test them in the field.. a job for another day.