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Darwin:: AS you have already been advised, receiver noise has two sources, Radiated and conducted. Conducted noise is usually caused by poor ground connections between the engine and airframe, rusted and corroded connections, pitted points on the voltage regulator, generator brush bouncing and arcing (in need of an overhaul) and unshielded wiring in the engine compartment. The Older Ercoupes had a large noise filter on the generator output lead mounted on the firewall when the radios were installed at the factory. These filters are still available at various supply houses. The filters must be capable of passing all the current from the generator (about 35 Amps) and are about 2.5 inches square and an inch thick. If the noise is radiated, ie: picked up by the antenna of the radio, it is usually the result of poor antenna placement and grounding, poor spark plug wiring, bad or improperly installed coaxial cable, or maybe the radio itself is poorly designed to operate in the hostile environment of an operational aircraft. It is well within speculation, that the wiring in a 50 year old airplane is in poor shape. Check the bonding between the engine and airframe, it should be a braided strap, properly bonded my a screw to the block of the engine, and an unpainted surface on the firewall. check that the mounting of the grounded connection on the antenna lead at the antenna end is still intact and bonded to the airframe with a tight captive screw. Check to see that suppressor or shielded wiring to the spark plugs is intact and properly mounted. See that the spark plugs are the resistor type that is specified for you engine. In short: an inspection and repair of the wiring of your aircraft will remove a great deal of doubt as to where the problems are. At the time the Ercoupe was built, off the shelf aircraft radios did not possess the sensitivity, and noise limiting attributes found in today's modern aircraft radio, and attention to detail in the installation department will provide many rewards. I will have to give you some words of wisdom from an old College professor of mine who spouted this advice about the time your aircraft was going down the assembly line. "If you don't want to spend a lot of your time chasing radio noise, don't create it!" I hope this helps Wayne -- Mr. D. Wayne Woollard, CPBE AIM: DWWoollard ICQ: 124132836 "Why fly a Spam can when you can have fun and fly an Ercoupe?" ================================================================== TO UNSUBSCRIBE go to: http://ercoupers.com/lists.htm
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