Ultralight aircraft radio noise - minimizing engine noise in your ultralight radio and  intercom systems.

Most strobe driver units are designed with filtering and internal shielding to keep radio interference to a minimum, however occasionally noise will be heard over the radio or intercom This noise is almost always caused by the way the systems have been installed.

One must remember that noise does not always come from the power that is being supplied to your equipment. Especially if the radio has it's own power source (battery ) and the strobe is powered by the aircraft battery. Installations vary greatly from aircraft to aircraft. Do both systems share the same power source?

Is there an external antenna? How close is the antenna, radio, wires, etc. to the strobe driver box and wiring? If both systems are not sharing the same power, then where is the common thread? In most, if not all cases the problem is GROUNDING.

The ground path is very, very important. The strobe circuit draws high current through the ground circuit. The radio, intercom, head set and mike circuits use that same ground so it is important that there is NO voltage drop between where all these grounds are connected. In other words lets say the strobe driver is getting negative battery or ground from a bus near the battery that is also grounded to the metal frame of the aircraft.

The ground plane for the radio antenna is connected to the aircraft frame further back near the tail and the radios are grounded near the cockpit to a screw in the frame. This array of connections can be a source of noise. The following list is intended to help in eliminating noise.

1. Power for the strobe system should be on the first fuse of the power bus. In other words the closest fuse to the battery.

2. The strobe driver's metal case should be solidly connected with a ground strap or 16 ga. wire to the aircraft ground system.

3. The audio ground and aircraft ground should be commonly connected only at ONE SINGLE POINT. Ground all the audio equipment; radio, mike, antenna, headphones, intercom, etc. to an "audio ground bus" (16 ga. or larger wire). Then connect that bus at one end only to the aircraft central grounding point, preferably near the point the battery is grounded.

4. Do not run audio related wires next to power supply wires.

5. Shielded wire is not normally necessary, however, if it is being used ground that shield at only ONE end. Usually the end closest to the source.

This list has been derived from the fixes that have worked for others. If you find something new please let us know and yours will be added to help someone else.
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