Most designs are based around the 1N34A Germanium diode, Clifton Laboratories has an interesting article comparing the following 3 diodes as alternatives;
1N5711 Schottky signal diode
1N270 Germanium signal diode
1N4148 Silicon signal diode
The 1N270 came out tops with the 1N4148 being the least desirable of the trio.
So why build a RF probe? Besides being handy for a number uses, the primary purpose for which I needed an RF probe is for detecting RF output from the finals of my TS820S when neutralising
the new output tubes.