After a number of failed attempts (with HMC799, OPA859), here is a reasonably fast One Inch Photodetector using OPA818, a FDS015 photodiode, and 1.2 kOhm transimpedance. Bandwidth is above 400 MHz, with the dark-noise and frequency-response in reasonable agreement with TIASim predictions.
With the detector blocked there's quite a lot of electrical feed-through with just the spectrum-analyzer TG-output on (see blue data points, especially above 1 GHz). I tried to correct for this roughly, shown as the orange data points.
Slow pace today due to both tired legs and slow greenish terrain. The controls were grouped into two groups with a slightly boring 'tunnel' run between the areas. OK until #4, but not the greatest direction towards #5, and then after wading through the swamp and green area towards #10 I decided from within the control-circle to go check that the yellow swamp on the right really is there... (#10 was probably the hardest control on this map). Good weather around +18 C.