Date:	9-11-2010
Number of Hours:	3.00
Brief Description:	Radio interference
Today I played around with the transceiver and discovered a few things that I’ll have to address. First of all, whenever I pressed the PPT button, the EFIS display changed – I would get Cylinder head over- temperature alarms; which would disappear as soon as I released the PTT button. Since the GPS antenna for the EFIS is pretty close to the radio antenna, I thought maybe this was the problem, but I placed a large piece of aluminum foil over the GPS antenna, and keyed up the transmitter and the EFIS still went into CHT alarms. This should mean that the distance between the radio antenna to the GPS antenna for the EFIS is not the problem. I’ll have to install some more RF chokes (ferrite beads) to the incoming wires for the EFIS and make sure these wires are as far away from the antenna cable as possible. I may also have to install another shield around the antenna cable. Another thing I discovered is that I can hear electrical noise in the receiver from the EFIS. With the EFIS on, I can hear an electrical noise in the head set, and with the EFIS off, the electrical noise goes away. To correct this issue, I’ll have to install a large capacitor between the 12V and ground busses - something I probably should have done from the start. If that doesn’t fix the problem, I may have to install ferrite beads to the power connections to the transceiver as well.