Hi Ramy
One of us is misunderstanding the Flarm operation. Assuming 2 aircraft each with a PowerFlarm and a transponder all powered on they should talk to each other in Flarm language. The PCAS function will be ignored and not displayed. Turn one of the PowerFlarms off and the other will detect the transponder from the plane without the operating PowerFlarm. It will do this in PCAS mode. Then reverse this by switching on the off PowerFlarm and switching off the on PowerFlarm. This will allow you to check the PCAS performance of both PowerFlarms.
So you do need 2 aircraft plus 2 PowerFlarms to perform these tests but because of the criticality of the positional of the antennas I think most people after installing PowerFlarms will want to do these tests with a partner aircraft to check performance.
Dave