Why does Harald Blue work and the smart phone apps don't?
Bjarke (our inventor) wants to address using a smartphone for contact tracing is not effective. In the graph below, various phones have been measured for their radios signal strength at 2m. The smart phone app can report you as infected when it reports 'RSSI > -65', and in the article it is clear that this all depends on which smart phone you have... possibly infected ... or not.
This comes from a technical article that also points out that it depends on the phone's orientation and placement on your body. For example if you have the phone in the back pocket versus front pocket, you can add/subtract 15 to the number in the graph above, moving the target from anything between -50 to -80. The result is you could be 5m away and seen as infected and holding hands and not seeing as infected....
Harald Blue has a set BLE energy across all units, set and calibrated during production. Therefore, the distance results are consistent, as long as everyone wears their units on a lanyard or clipped to their chest pocket.