Following my purchase of the Sotabeams WSPRlite WSPR beacon a few weeks ago I have just built the optional Low Pass Filter (LPF) kit for operation on 40/80/160m which I will primarily use for 40m. You can see my review of the WSPRlite unit on our club’s website.
The first stage of the build is to wind the inductors - I haven’t wound a toroid before so my first attempts were a little daunting but the instructions from Sotabeams included a link to a website at Genesis Radio offering some simple guidance which seemed to work well. It’s a bit fiddly and with some toroids needing 30 or more turns so you do need to keep count! I stripped the enamel coating ready for soldering by scraping the required length with a sharp scalpel. Once complete these were soldered into place on the board and continuity tested both in isolation and in series using the solder pads for their neighbouring capacitors as handy test points as per instructions.
Soldering the tiny capacitors into place was straightforward, as were the header pins, coax tail and SMA socket.
Next step is to test the LPF in operation, maybe you’ll spot my (clean, filtered) 200mW WSPR transmissions soon :)
Please see the photos attached.