Mike,
This article will give you more info than I can ever type out?
Only difference is I used SMA jacks instead cable pieces and slightly longer probes since I did not needed it to be too narrow band. I used a 1-1/4pipe cap I had on hand from a plumbing project and instead a PC board I used a piece of hobby brass sheet 0.02 inches thick I bought at the local craft store a while back. It is not that critical as long as the cap isn't too big.
John
John Cunliffe W7ZQ