“It has to be a big thing to show on primary radars?”
Use military technology to detect primary radar pulse and send spoof echo?
And that spoof echo can spoof its distance farther away from actual position, and changing.
Peter wrote:
It was the carriage of a Mode S TXP on a model plane which this was about.
It has to be a big thing to show on primary radars? some will say that anything with less that 10lbs/ft2 wing load does not generate enough electrics to power a ModeS but you only need one 30 seconds blip for CAIT to generate a report 
I am reliably advised 150kt is not a problem for a model plane.
It was the carriage of a Mode S TXP on a model plane which this was about. ATC is not monitoring ADS-B so you could not get somebody into trouble with spoofing that (in Europe)
alioth wrote:
It won’t fool anyone because the distance and speed of a model plane will generally be too low
You can spoof ADS-B from the ground without having to do any flight. All you need is a rogue transmitter programmed to emulate a flight.
What happens if the guy keeps flying with your transponder ID ON while you & your aircraft are grounded? aircraft is stting in the hangar and you are shopping at Tesco, both can be substantiated with irrefutable proofs
That’s all true but in the situation you describe the CAA will suspend your license immediately, probably (according to my info) with a phone call made by The Man Himself, backed up by an email, and then you (i.e. me) have to sort out the mess.
Peter wrote:
but we don’t seem to hear of it happening.
Probably because it won’t fool anyone, and it’s too easy to get caught. It won’t fool anyone because the distance and speed of a model plane will generally be too low, and would (hopefully) be noted in the MOR that the aircraft appeared to be flying unusually slowly/go an unusually short distance.
Now let’s suppose someone does it with full scale, they fly to a field somewhere, reprogram their transponder (which is trivially easy to do) with your Mode-S id, then fly right through Stansted’s airspace or something. You get the nastygram from the CAA, look at your log book and…hold on, I wasn’t flying then. Shoreham can of course back you up because their logs show you weren’t flying.
If you were flying, you can say “Actually, I was flying through Wales (or wherever) on that date and time” and again, this can be confirmed. Other things too, like you don’t generally fly your TB out of random fields.
Depends. Climb if CAS not an issue, otherwise turn. Prob99 the other guy has not seen me 
In an extreme case turn away and do a 360 orbit.
I think there are good reasons why these systems are not spoofed. ILS is probably harder than it seems, due largely to the signal monitoring, and most vandals being thick as a plank. And spoofing ADS-B will be pointless because nobody – outside the US, perhaps – is using it for anything serious
It’s always been trivial to do windups by mounting a Mode S box, with the ID of somebody you don’t like, on a model plane… but we don’t seem to hear of it happening.
Peter wrote:
I always use my TAS605 for active avoidance, because even with 2 or 3 people looking out, most targets are never spotted visually, so if something is conflicting, one can’t just sit there and hope….
How that works? you fly opposite heading? or 90deg away?
I tend to rely on altitude data for avoidance, it’s easy to get +/-500ft or +/-1000ft vs target transponder altitude while keeping my heading and keep looking ahead
Same, I always managed to avoid conflict but I rarely managed to spot the guys visually by turning my head back, left/right but anyway I don’t care as long as what is ahead is clear (maybe only applicable as I fly at 150kts )
That may indeed be written but everybody around here is using it for avoidance maneuvers. Especially when one sees how many of the “velcro attached gizmos” report only distance and relative altitude, no bearing. I always use my TAS605 for active avoidance, because even with 2 or 3 people looking out, most targets are never spotted visually, so if something is conflicting, one can’t just sit there and hope….
