thanks anyhow

btw why is the picture so blurry?

High power transmitters are banned pretty much everywhere I know of, you’d need a proper license to operate them, but that’s obviously not enough to detour me… I however don’t have an oscilloscope so I wouldn’t be able to troubleshoot / optimize the circuit even if I wanted to build one, but there are quite a few out there — you should keep looking!

You can make a variable capacitor at home, you should be able to reach at least 20pF with a piece of aluminium and some cardboard, or a book. Otherwise you can try building a proper one with aluminium sheet, nuts and bolts! – The other idea is to use two pieces of copper clad board, arranged in a way that you can rotate one of them to change the capacitance, you can actually use double sided copper clad to make a capacitor as well. These tiny trimmer caps are nothing but thin aluminium sheet with a dielectric, usually very similar to the plastic used on transparencies, etc. They’re actually very cheap to manufacture since the metal pieces are stamp-cut, but sometimes they’re not so easy to find specially if you live in a small town!

If I had a proper LCR meter capable of such low ranges I’d probably experiment a bit with those ideas, but keep in mind that almost anything adds capacitance when you go down to a few picofarads anyway… So it’s a tricky situation!

pity i dont have any trimmers so i wont be building this one any time soon im afraid