To really test the setup I have here I tried testing a 2N2369A transistor. This is from an old bag of samples of the ST (SGS Thompson) version of the 2N2369A. I have had these samples in my parts stash for many years. I think I used these for crystal oscillator prototyping at work back in the early 1990s and so these are genuine 2N2369A parts and not modern clones/fakes. To get a sensible result from the scope up at 700MHz I had to set it to repetitive sampling and I tried testing at 10mA Ic and 10V Vce. The test jig showed the Ft was 715MHz. Note that my old 500MHz scope doesn't have to be accurate in absolute terms as it is just looking for the same AC voltage at the base and collector when at Ft. The Marconi 2388 1GHz RF probe has an input capacitance of about 2pF so it should be OK here when probing across a 10R resistor.
This really is stretching my lashup test setup to its limits but it does seem to agree fairly well with the 2N2369A datasheet as it states 675MHz Ft at 10V Vce and 10mA Ic. However, I think it is better (as in more traditional) to measure the 'gain' at a lower frequency and extrapolate the Ft using equations. This would put less stress on the accuracy of my test setup as long as care is taken with the measurements and the maths. I've never tried this though. I always just look at the datasheet for this stuff
