Pictured below is my Single Coil Toroidal Z-Match which follows a design by Lloyd Butler VK5BR .
This uses a T200-2 toroidal core and a couple of receiver type variable capacitors which allow a max input power of about 50 watts CW . This depending on the aerial in use i.e. short doublets may cause problems on lower bands but I used a 50ft doublet on 80m with no problems, though down on efficiency.
A hole was cut in the box lid to allow clearance for the capacitor vanes and a perspex cover added to keep dust out etc.
Vernier drives are great for this application but hard to get at the right price these days. Got these at Maplins years ago.
Hope to build a higher power version with air-cored inductor soon..
|Single coil toroidal Z-match (QRP)|