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RF Interference and the MZ202 Engine

Hi all,

I received the below e-mail from Lance Lehto regarding the fix I incorporated on my XEL to reduce/eliminate radio interference (hiss) from my Microair 760 radio. I decided this topic was one that all Mosquito owners who install aircraft radios in their machines probably would want to read. Some of the references in this post were buried in another thread titled "MZ202 ignition wiring update". All too often on this site, we embed secondary topics in threads and no one knows these topics are there. Anyway I've made this a frontline thread with reference to the main thread where it first appeared.

Here is the Ignition Wiring Update site location:;posts=44



Sent: Sunday, May 04, 2008 7:56 PM

Hi eddie,
      I am having a tough time getting my handheld radio to work with the xe.  I would like to know exactly what equip. you used to get the good results you report.  Has anyone else got a working radio on the mosquito that is different from yours?
Thank you for your time,
Lance Lehto

My radio is a Microair 760 panel mount radio with 4 watts output power. I installed a 13Db attenuator on the output connector, in-line with the antenna. The input gain is reduced, which effectively reduces the noise the receiver  sees. This eliminated the (hiss) side tone which could not be controlled with the radio squelsh control. The trade-off is reduction of the effective radiated power at the antenna when in the transmit mode. This is not a problem when the radio is used within several miles, but would be a problem if used long distances such as talking to, for example regional air controlers or any other long distance transmissions/receptions. I think you could achieve the same result with your lower power handheld (probably rated at around 2 watts) radio by installing attenuator(s) with lower Db ratings.
Attenuators are available at Radio Shack, and they are 3Db. You can connect multiple attenuators in line to achieve the result to best suit you. You will have to also buy connector adapters to get to the BNC or TNC connectors that your radio probably has. Play with the Radio Shack adapters to get a combination that gets you where you need to be, as one adapter probably won't get you there. At least, that was what I found in my case.
Hope you find success, as I did with this approach.
On the Mosquito Website, Oskar went through a systematic shielding exercise in an attempt to reduce noise on his handheld. He achieved a reasonable result, effectively reducing(but not totally eliminating) the noise to an acceptable level. His effort was a massive shielding effort where he had to dissect harnessed(s) and shield boxes, etc, etc, etc.
Click here to read Oskar's detailed report on his radio interference testing/resolution:
After reading his detailed analysis and report of all he had done, I decided to do some shielding in my noise reduction was achieved. After thinking this over, I thought of the attenuator approach as a possible solution with acceptable trade-off. It worked, and is a simple solution to implement. The cost is less than $10, and can be undone by simple removal of the screw-on attenuators. 
I hope this will work for others as well as it has for me.
Hopefully, Lance and Oskar are OK with me posting their info without me asking first.

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