The problem is, I’ve never seen power supply noise or anything remotely close to 1 kW, which is why I suspect something is seriously amiss. My first thoughts turned to external influences. Where it’s going wrong is the hard part. A near-correct reading on his kettle indicates it’s not a stupid calibration value that’s crept in, and the burden has not fallen off.
Those are sensible numbers.
Those aren’t sensible. They indicate the c.t. cable, or the c.t. itself, is picking up something.
Now that’s ridiculous. It seems to be seeing an electric field on the kettle lead.
There should be no difference between the c.t. being unplugged, plugged in and not on a cable, and on a not energised cable. In practice, it’s hard to get away from electromagnetic fields, so you do expect a small increase when a c.t. is connected.
@Guff666 might want to update his sketch: In The emonPiCM I published a sketch for the emonTx V2 using emonLibCM and the native RFM69 radio message format. It’s relatively easy to change it to use the classic JeeLib message format - simply change #include <rfm69nTxLib.h> to #include <rfmTxLib.h> and most likely also change #define RFM69CW to #define RFM12B and I think it should work. I don’t think this will solve the present problem.