Tim, thanks for your response.
I have been using a Zaon MRX PCAS for six years in a PA28 averaging 100hr per year mostly VFR but with some IMC. This device gives nearest transponder mode C/S within 5nm and +/- 1000 ft but no Azimuth. However one can keep an eye on range/ALT changing and figure out the threat. Radar or TCAS has to be interrogating, so the transponders reply and the Zaon device picks this up.
I have found it very useful. I read all the Airprox reports and time after time they say both aircraft equipped with mode c/s but
nobody was carrying a detector.
Sadly my detector has just gone u/s.
There are a lot of transponder equipped GA aircraft out there and it immediately feels uncomfortable not to have the device.
SE2+SD with this basic feature would be a very good idea and of course there would be the other traffic warnings from
ADSB and Flarm.
Some might think not having Azimuth is a serious drawback but I bet they have never used a range/ALT device over a
long time as I have.
I trust you are right about the long term but a SE2 would be ordered tomorrow if you said you would fix my problem and I
would not worry if you were going to collect an extra £ 30 per year from me just for the mode c/s traffic info!
Keep up the good work