automan1223
09-18-2008, 07:14 PM
I have been doing some homework on the EMI / RFI problem on my powerplant and VHF radios. My yaesu radio with an aftermarket antenna was useable but could have used a lot of improvement.....Robert lent me his nice ICOM 24 and the emi / rfi noise I believe is coming from the ignition system was so bad the squelch was held wide open. No trick antenna was going to cure this. I am guessing the ICOM is a too sensitive radio. Even though the pro ignition wire set I have has additional metal shielding braid over all the wires the pop pop pop is too much and I feel it has gotten worse over the 200 hours I have flown....
I came across several articles that listed the usual places for interference. Step one is to use good shielded wires. A mfg name of good high performance ignition wire, Magnecor keeps coming up and I will be ordering some wire from them very soon. Like the story goes you get what you pay for.
www.magnecor.com
The second issue was having the distributor cap "flame sprayed" by a company that coats all sorts of things to EMI / RFI proof them. THe process plates a metal coating over the cap effectively isolating it to ground. I am guessing putting a metal coffee can over the distributor might have the same effect but would be unwieldy. Possibly a custom fiberglass or carbon fiber cover could be mfg'd and flame sprayed.
http://flamesprayinc.com/
I spoke with the owner of the establishment. Darrel called me back later today and was all too happy to talk with me about flame spraying, etc. Fact that he coats jet engine parts and is a FAA certified station helps. I did not have the courage to tell him this was for an experimental aircraft since I want to see what the results would be before I go getting a bunch of stuff coated. And given the chilly reception we get to other areas of our parts needs and other stuff....But I was amazed at how many applications there are for flame spraying, or thermal transfer process.
in another article I came across this tidbit about electric fuel pumps.
FUEL PUMPS
This has become a problem in many Ford vehicles. Ford's Technical Service Bulletin, TSB-93-15-6 covers this RFI problem.
They offer a fuel-pump filter that installs in the tank, right next to the in-tank fuel pump, which, if not covered by warranty,
is a real pain to install, and may not work if you have a non-metallic fuel tank. The part number for the filter is F1PZ-18B925-A and may cost up to $60.
A cheaper and much easier solution that some have had success with is to wind BOTH power wires going to the fuel pump around ferrite cores.
I think that this problem is not local to fords, but might just be that they used a lowest bidder that built a really cheap pump with no electrical considerations.
Knowning how many of us run electric pumps putting some effort into isolating and reducing the noise
Here is a link to a very good article I found and while it is a few years old I am sure many of the tactics can be used in our aircraft.
http://www.arrl.org/tis/info/pdf/001qex32.pdf
Lastly here is a link to some emi / RFI filters ......
http://www.specemc.com/docs/EMI_Power_Catalog.pdf
Jonathan
I came across several articles that listed the usual places for interference. Step one is to use good shielded wires. A mfg name of good high performance ignition wire, Magnecor keeps coming up and I will be ordering some wire from them very soon. Like the story goes you get what you pay for.
www.magnecor.com
The second issue was having the distributor cap "flame sprayed" by a company that coats all sorts of things to EMI / RFI proof them. THe process plates a metal coating over the cap effectively isolating it to ground. I am guessing putting a metal coffee can over the distributor might have the same effect but would be unwieldy. Possibly a custom fiberglass or carbon fiber cover could be mfg'd and flame sprayed.
http://flamesprayinc.com/
I spoke with the owner of the establishment. Darrel called me back later today and was all too happy to talk with me about flame spraying, etc. Fact that he coats jet engine parts and is a FAA certified station helps. I did not have the courage to tell him this was for an experimental aircraft since I want to see what the results would be before I go getting a bunch of stuff coated. And given the chilly reception we get to other areas of our parts needs and other stuff....But I was amazed at how many applications there are for flame spraying, or thermal transfer process.
in another article I came across this tidbit about electric fuel pumps.
FUEL PUMPS
This has become a problem in many Ford vehicles. Ford's Technical Service Bulletin, TSB-93-15-6 covers this RFI problem.
They offer a fuel-pump filter that installs in the tank, right next to the in-tank fuel pump, which, if not covered by warranty,
is a real pain to install, and may not work if you have a non-metallic fuel tank. The part number for the filter is F1PZ-18B925-A and may cost up to $60.
A cheaper and much easier solution that some have had success with is to wind BOTH power wires going to the fuel pump around ferrite cores.
I think that this problem is not local to fords, but might just be that they used a lowest bidder that built a really cheap pump with no electrical considerations.
Knowning how many of us run electric pumps putting some effort into isolating and reducing the noise
Here is a link to a very good article I found and while it is a few years old I am sure many of the tactics can be used in our aircraft.
http://www.arrl.org/tis/info/pdf/001qex32.pdf
Lastly here is a link to some emi / RFI filters ......
http://www.specemc.com/docs/EMI_Power_Catalog.pdf
Jonathan