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EMI / Radio Static
#1
HHHHHAPPY DANCE!!!

When flying the other day I could actually hear something other than static and I could talk on my MGL 760 dash mounted radio in flight to the airfield and to a fellow pilot flying a loose formation with me. Wow, without static and noise in the reception or transmission. That's an ohhhh hell yeh!!!   after years I finally stumbled on something that worked so to share on what I did......The disclaimer up front --  I did all the mods at once so I don't know if it was one thing or all of them combined.  Also I made my own wire harness so if yours is stock you will like have to do some cutting and soldering.

The what and how come - I read up on Electro Magnetic Interference (EMI) and found basically its either transmitted in the wire from its source or through the air and is picked up in the wires like an antenna or is like a big bubble of interference or combinations of all the above. On the MZ202 the alternator stator spinning around creates a magnetic field which is constantly collapsing making electricity and creating the EMI.

So first 1) thing I did was put shielding on every wire coming out of the engine. The ones coming from the magnets on the sides under the carb and behind the starter motor and the one going to the voltage regulator and because there easy on the spark plug leads.  I bought different sizes of shielding from Wick and you'll need shrink tubing to secure the ends.

The next 2)  was I put a good ground directly from the battery to the base of the starter mostly because I felt it wouldn't hurt to have a redundant ground. 

Next 3) I put a ground on the splitter gear box, (the how come redneck engineering), I figured the tail rotor blade and tail rotor driveshaft are spinning around generating static electricity and it doesn't have a good way of grounding it could be arching, making noise, this idea is based on what I've seen in the way of damage on the motor mount shims and also on my fuel pump mounting brackets. To me the damage looks like arch pitting so I wanted to mitigate it (pictures in the gallery).

The next 4) The cooling fan shroud is plastic in my reading I found that EMI transmits right through plastic so I figured the biggest source of the EMI is coming right off the bottom of the engine and would look like a big donut with me and the radio in the middle so I built what I consider a containment. I took the shroud cleaned it good with carb cleaner and then sprayed it with adhesive and coated it granulated copper - I did it three times adhesive and cooper dusted on then painted the whole thing with paint to hold it together. You could probably accomplish the same thing with some kind of paint that's high in metal content but I used what I had.

At any rate with the combination of the four things I was talking to the airfield about three miles out and air to air without static or feed back, confirmed by the other pilot.  I haven't explored the effective range yet just happy to be able to hear without static and talk to where ever I want to land     

pictures in marcher gallery under EMI  http://forum.mosquito-helicopter.info/ezgallery.php?su=user&cat=223&u=637

were I to prioritize I'd tackle this in the following order
1) ground the splitter gear box
2) the starter if you have a mind to
3) coat the inside of the fan shroud with some kind of conductive paint or like I did because its easy to do
4) check the progress of all the above
5) tackle the wire shielding - this being last because it requires disassembly and surgery

Hope it helps
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#2
Mike 
great info
I have a related question for you, I've mounted a compass on top of my instrument panel I checked the heading
in flight with my gps and the numbers are ok. When turning on the master switch the compass dial twitches I would like 
to put something under the top of the panel to block the mag field what do you think I should use

chuck
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#3
Chuck 
No sure what you would use you might try shielding the wires to the switch see if that would help,  I'm more along the lines of If the compass and GPS line up in flight let's go flying 
Mike
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#4
Thank you for the info Mike. I will try the same solution in the priority order you gave and test it after each point. Right now I have zero transmission and can receive (badly) only at idle.
What did you ground the splitter gear box too?
Richard
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#5
Thanks Mike
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#6
I am going down the steps as you recommended. Step 1 splitter box, no appreciable improvement, tomorrow step 2
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#7
(08-28-2016, 03:21 AM)Richard Italia Wrote: I am going down the steps as you recommended. Step 1 splitter box, no appreciable improvement, tomorrow step 2

Grounding the splitter I think will help mitigate the pitting of the spacers on the motor mount and maybe some on the EMI noise -- any help on the noise is a good thing -- feel like I should do like tv or radio lawyers adds  "results may vary"
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