I wasn't conducting a clinical observation of the Xaon PCAS. I was using it operationally, in a high-density traffic environment. All aircraft were squawking with a transponder. Nearly all operations were conducted at night, and radar was in use.
When I stated that much of the traffic wasn't reporting, it was because much of the traffic was unmanned, and much didn't use voice capability. Many of the aircraft used other means of communication which will not be discussed here, but which was available to ATC, but not to me (also for reasons that need not be discussed). The area was a combat zone, not a war zone, which has no impact nor bearing on the ability of the PCAS to do it's job.
The PCAS was used in numerous aircraft in numerous locations and conditions, with substantial traffic, in an environment very conducive to observation of it's function. Specialized equipment was available to see areas where traffic was identified by the PCAS, and verify that the traffic was indeed there or not there, and that equipment was operated by very experienced specialists who were amazingly good at what they did.
Now as I said, I didn't undertake the mission to test the PCAS. It was installed as an expedient field-procurement, and while it did have numerous false warnings, I did give positive hits which were immensely useful. I operated in an area where numerous threats existed. From a pilot's perspective, in my opinion, the biggest threat wasn't ground fire or other concerns, but the potential for a mid-air. I was interested in anything which provided additional traffic information, regardless of the source. With numerous resources available, the PCAS was but one reference.
The Xaon unit displayed numerous false targets, sometimes proving to be a distraction. In some cases where I could verify a false indication, it proved little more than a distraction. In other cases the distraction interrupted other activities while I verified what was being received, and it caused problems. I did have the PCAS alert to traffic which wasn't reported by ATC, which had been assigned to our airspace block by other entities, without any communication to local control or to us...and a certain amount of traffic in those areas operates autonomously. For these and other reasons, I was always well aware of the traffic information, and always included the information in my scan, and took it seriously. It had many false hits, but also provided useful information that sometimes wasn't available from other sources.
In general, the PCAS did provide some useful information, but also distractions, and did display a fairly high false-positive rate with failures. Transponder strength was addressed, as well as positioning, and onboard equipment was considered, and tested.
While I appreciate that you've had different experiences, you have no reason to discount my own. Certainly anyone considering spending the money to put one of these in their Cessna 172 shouldn't consider any available report. Perhaps you've had a good experience and feel threatened if a report of poor performance devalues the money you've invested. Perhaps you're personally invested in your PCAS. I have no idea. Perhaps you even sell them. No matter. That you don't like the fact that the units were observed to perform underpar means little. The units did perform fairly poorly, and this is fairly noted. By all means, publish your good report, and let others who read both decide for themselves.
TAS - try a Google search, or perhaps you need a little help.
Okay. Googled it. Nothing of value returned...unless you want to talk about "The American Spectator," "The Absolute Sound," "Texas Accessibility Systems," "Tactical Archery Systems," "TAS Turkish Restaurant," "The Animated Series," Tasmania Ferry Services," "Tata Administrative Services," "Tasmania," "Turbine Air Systems," "The American Statistician," or any number of other things that were returned.
I get it. You don't want to answer the question, and would prefer to be difficult. Good enough.