I flew, this afternoon. The weather wasn't particularly great but I wanted to test my new EFIS module (electronic AI, for backup purposes), the conditions were good enough though, for my abilities.
As per normal, I had the PCAS unit running. On the return to Shoreham (from the SFD area) it picked up several transponding a/c, most of which I was then able to locate visually, based on its information. I suspect that without it I may have not seen many of them (due to not knowing where / when to look). The local visibilty was variable but generally poor at the time.
One part of the flight concerned me though. After leaving Shm, on an Eastern track (for SFD), an a/c passed me about 100ft (barely) below on a reciprocal heading. The PCAS picked up nothing (before or after), suggesting that the other a/c was not transponding. It was a reasonably sized 4 seater a/c.
I find it a bit irritating that such an a/c which could probably have been able to squark mode "C" did not do so???