Mag Filters For My 2200
In an effort to eliminate, or at least reduce, RFI, I purchased magneto filters from Lone Star Aviation. Unfortunately, after installation, the engine won’t start. If I remove the filter, I have ignition. I installed the filter in series as per the installation diagram. There really isn’t a wiring diagram, it’s an installation drawing. The filter is designed for Bendix mags so maybe this is not the correct application for the crude magneto on the 2200. Its capacitance is rated at .05 uf.
And yes, in my quest to combat RFI, I made shielded high tension leads, replaced the p leads with shielded wires with the shielding grounded on both ends, changed over to RG 400 antenna cable, cleaned the ground plane on the antenna (aluminum construction but painted under antenna mount).
Any experiences out there using a p lead filter? What about RFI; what have you done to reduce it.
PS. The interference is a sharp crackling noise that changes with engine RPM. It’s not an whine that you would hear from EMI; motors, alternator, strobes, etc...
Alex R -
I haven't tried a capacitive type filter on the p leads. I would earth the p lead shielding on only one end. Being earthed at both end could introduce a ground loop.
If you haven't done this already, try to determine if the interference is getting it the system via the antenna or via the wiring i.e noise on the earth circuit.
As always, I appreciate your prompt replies. Does it make a difference which side to remove the grounded shielding on the p lead - at the switch or mag?
Alex R -
\I don't think so. Which ever is easiest.
Any updates? I am experiencing similar EMI/RFI issues on my 3300L. I know many will cringe at me doing this but I adjusted the carb idle screw so I shut the down and disconnected the p-lead at the MAG. I still had the EMI. Based on the note above I’ll disconnect the coax at the radio and see if that has impact. I also plan to install shielded p-leads. I also only grounded the headset leads at the radio end to preclude a grounding loop. If nothing else works I’ll try grounding headset at both ends. Any other suggestions? Regards, John - N2AOO
When I bought the plane, the Garmin SL 40 was inop and I purchased a drop in replacement, Icom A210. I’ve read where some com radios are more susceptible to interference and thought that replacing the radio with the original Garmin would help - it didn’t. After all that was done, in my opinion, the lawn mower grade magnetos are the culprit. I’ve considered purchasing Rotec’s electronic ignition so that at least if the interference was so bad that it compromised communication, I can shut down the mag and use the electronic side. So I still fly with the RFI. Some days are worse, some better. The weaker the signal, the more pronounced the noise. I hesitate to fly into controlled airspace as a result of this and stick to uncontrolled fields. I wish I had better news.