I asked the question below and it is posted now. Here is a great response recieved. Might help.

I started to read Dan Williams article, “Broadband Over Power Lines”, from April’s Model Aviation with great interest. In the article, Dan mentions interference from metal-to-metal noise from linkages. I want to present this topic at a technical / detailed level at a club meeting and would like to understand it fully. Can anyone either fill me in or provide where to find?

John 373786

Given that 99% of interference emanates from within our own models, I'll provide the following explanation-

There are two primary sources of interference, ignition and metal to metal. Ignition noise (relates to gas engines of course) is broad spectrum RFI radiated from the ignition system when the plug fires. This is a no brainer. Nothing more need be said about this form.

The second form is a result of two similar, or worse yet, dissimilar metals abrading. This source is caused by Thermo Electric emc’s. When there is a difference in temperature between two dissimilar metals, a current flows. The friction and vibration provide for that temperature difference. These currents can be quite large depending upon the frequency, or rather the magnitude of make/break contact of the two metals. The magnitude of the make/break is provided by the vibration of the models engine.

The currents generate and radiate RFI in a similar manner the ignition circuitry. Due to slight differences in the metalurgy of same type metals, these currents also flow in similar metals but at a lesser magnitude.

Interference from other sources such as automated machinery, remote controlled cranes, etc. are very rare. These are the items that make use of frequencies between ours. Unless you’re flying from the parking lot of one these facilities or construction sites, the likely hood of be interfered with is negligible.

You stand more of a chance being shot down by your buddy at the field switching on by accident.

There’s a third source of interference we experience as a result of conductive emi, and associated anomalies due to high transient currents and supply distribution within the model. This however is controllable through methods such as separating batteries for servo and receiver. This type of emi interference has little to do with this topic, though.