Acorn 6210MG/5210MG Wireless Camera Instability - Continuous Triggering

Fig 1:  A lot of nothing!

There have been a lot of theories floated about recently regarding the problems with Acorn wireless cameras released since last December with the new SIM900 GPRS Module.

The new GPRS module is supposed to have a higher output than the old M10 and although I don't have the means to measure this accurately I'm fairly certain I've worked out what's happening. When the camera is triggered and tries to send an image (doesn't matter if it's MMS or SMTP) the RF output from the wireless module is causing interference with the camera PCB and upsetting its functions. 

Continuous or self triggering:

The amount and type of interference varies from camera to camera.  In particular the interference will cause self triggering in both MMS and SMTP  modes, but as I said before. not in all cameras.

Continuous or self triggering is the most annoying and undesirable of the problems caused by this interference but remove the SIM card and the camera behaves normally.

I had tested several of these cameras and was not getting any self triggering. In fact they were working completely OK sending via SMTP during bench tests and I couldn't understand why so many users were reporting this problem. Then I realised