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Radio Interference
#1
Has anyone had success eliminating the RF Interference problem?  I have a factory built XEL with an antenna in the tail boom. I'm using an Icom A6 and a seinheisser headset.  I get significant feedback when I power on.  so much so that I cannot use the radio.  

Any Help would be appreciated.  

Dave
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#2
https://www.dropbox.com/sh/vsiomcb1f1i7y...QkKZa?dl=0

Above is link to a long explanation of what I plan to do on my XEL. I am attacking the RF interference problem on 3 fronts (not worth doing unless it's overdone!!)

The credit must go to Oskar Stielau and the late Eddy Thompson (links to their research are listed in above article) who did all the original investigations. You may also wish to do a search under "RF interference" on the forum.

Have components ordered and shall attempt the cure next week when I get home!! Will post result when I can.  Let me know if there's any problems seeing the article I have in Dropbox.
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#3
Dave, I have the same problem as you. I have the ICOM A-24 and the Sirio antenna that Andy is using mounted in the same place as Andy's.
For those of you that don't have a dropbox account here is the info Andy spoke about....

Methods on XEL1144 in Reducing VHF radio RF interferenceInstalled on XEL1144 is a panel mounted Flightline 760 VHF radio connected to a no-ground-plane Airband antenna located on the Tail Boom. Because XEL1144 operates out of a tower controlled airfield, clear communication with the tower is imperative. As with other XE operators using panel mounted or handheld VHF radios, I have experienced a fair degree of RF interference on reception and especially on transmissions when the engine is at operating RPM. XEL1144 is powered by a MZ202 2-stroke engine. On this engine, the interference comes mainly from the ignition system. This is mostly due to the RF given off from the CDI ignition system of the MZ202. A second source of noise could be from the alternator (charging) system. Furthermore, the VHF radio suffers from considerable noise when transmitter is keyed. This may be due to poor antenna matching; lack of a ground plane in fiberglass aircraft to absorb the reflected RF energy; and due to ground loop phenomenom. My methods of reducing the interference is based on findings of Oskar Stielau (http://www.fennkayaks.co.nz/MZ202.doc)and the late Eddy Thompson. http://forum.mosquito-helicopter.info/sh...rferenceTo provide an all-emcompassing method of minimizing the noises, 3 steps were taken: IGNITION NOISE: --- a) The Left & Right CDI’s are enclosed in a metal box to absorb any stray radiations b) The 2 Coils are wrapped in adhesive copper foil tapes c) The Sparkplug leads from the coils-to-sparkplugs are enclosed in metal braided shielding d) Resistant type Sparkplugs are used ELECTRICAL SUPPLY NOISE: a. An inline power noise active suppression filter (Axxess AX-ANR1000) is installed between the Master Switch and the input to the Fuse Box to attempt to ensure a noiseless +12V power supply to the entire aircraft.
2Methods on XEL1144 in Reducing VHF radio RF interferenceThe filter is designed to actively cleanse noises generated by sources such as generators, alternators and inducted radio frequencies from the positive voltage line. GROUND LOOP NOISE : reference : http://www.mglavionics.com/EMI_suppresso...ncies.pdfb. A ferrite specifically aimed at the airband VHF frequency range is employed by wrapping the wires supplying power and data to the SUB-D connector attached to the VHF radio in order to stop the RF power reflected back to the transmitter. Lastly, sacrificing range for usability, a 10db inline attenuator is placed in the co-axial cable connecting the radio to the antenna. The input gain is reduced, which effectively reduces the noise the receiver sees. The trade-off is reduction of the effective radiated power at the antenna when in the transmit mode, cutting down the effective range of the VHF radio.
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#4
I never could get decent comms with my 301, 6 CDI's instead of two. Tried all the above fixes, finally accepted the very short range of my radio. I know others have achieved better results. Am currently installing a 285, hope it doesn't prove as difficult.
Skeeter
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#5
Dave:   Sorry didn't notice you mentioned you have a handheld VHF. John U. once mentioned that he folds the Rubber Ducky antenna back on itself and secure with strong rubber band. This effectively cuts the range of the handheld VHF. Give that a try.      Big Grin Andy
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#6
I still only use a handheld myself. To eliminate the noise issue I just place the unit in my shirt or jacket in front of my body which seems to shield the noise from the engine quite well. I haven't folded the antenna in some time. Folding seems to significantly reduce the range of the handheld.
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#7
I spoke with Dwight and we may have uncovered the issue in my case. I have a siro antenna that is mounted in the tailboom. I ran the antenna wire through the existing hole in the fuselage which is where all my wiring to the engine is. Dwight suggested that I drill a new hole on the other side and run the antenna wire by itself while making sure to keep the wires as far from the engine as possible. I'll give this a try and then update.
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#8
I have my antenna wire marked with green tape so that it shows up in the pic. It is in the tail and comes out below the fuel tank, runs behind the fuel filter and thru the same rubber grommet as the starter solenoid. The radio is mounted on the right side in the cab. I still have the interference. I also have the coils wrapped with copper tape.
Coils are wrapped with copper tape.


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#9
Hi all,

I've found that the digital MGL's creates a lot of 250kHz interferences. The ICOM handheld radio is not shielded agains this waves. The origin are the internal switching power supplies from each Instrument. You can easely testing it by switching off the intruments and you will discover a big drop of interferences. Only by turning off the display's back lights you will see that you have less interferences!

I have modified my instruments by adding filters (coil and capacitor) at the internal power supply.

Mike
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#10
Mike: sent you PM
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