SMA is threaded, and slightly larger. This has a push fit system with a clamping arrangement very much like the fastfit F-connectors. Outside diameter of the female connector is 3.2mm (+/- 0.1mm), SMA would be around 6mm.
The discone I have will hopefully raise the signal somewhat higher than the background noise. Will try tonight if there is a pass as I've just run a new aircored cable down from the roof for this specific job.