[RFI] ignition noise

WA3GIN @ Arlington County, VA wa3gin at erols.com
Mon Apr 24 12:46:08 EDT 2006

Also,  consider paths that transfer the unwanted signals throughout the 
vehicle. For example the brake lights. In one truck I had the screw 
driver antenna was mounted on the rear drivers side corner of the truck. 
When on 40 meters the stereo speakers in the truck would suffer 
significant RFI, even when turned off. The source of the interference 
was the brake lamp wires.  I bypassed them to ground and ran a dedicated 
ground from the negative side of the brake lamp to the frame rail.  
Problem solved.

RFI removal in an RV is just that much more challenging.  Many of those 
Chevy big block engines were installed with HIGH energy ignition 
systems. In the dark you can see the corona around the spark wires. Make 
sure the RFI you are hearing isn't coming from pick-up from the radio's 
12 volt supply wire that may be accepting an induced voltage from the 
near-by spark wires. One way to help locate the source would be to 
disconnect your antenna and install a dummy load at the coax end of the 
antenna connection. If that isn't easy to do, the install the dummy load 
at the radio. You may want to consider shielding your 12vdc supply lines 
or taking the 12vdc from house battery rather than the engine battery. 
Also, go direct to the battery, not off the house battery fuse block.  
You want a very low impedance connection, as high impedance means a 
welcoming environment for RFI.

I'd be very careful about using shielded spark wires in the P-30 truck 
chassis of your RV.  The temperatures by that engine with how the 
exhaust system is run are very high, reaching extreme operating 
conditions (perhaps one of the reasons the exhaust manifolds on those 
454s crack so often).

The "Ultimate" solution is to get your home station connected to the 
Internet. Then with a Verizon or Sprint EVDO wireless data connection 
you can operate your home station via the Internet. You'll have the 
advantage of a full-sized antenna, no spark noise from your RV or other 
vehicles on the highway. You can take your lap top with you anywhere and 
operate you home station, keeping local schedules, etc. It sure beats 
spending hours underneath the RV running bonding straps, haha.

Good Luck,
28 ft 1979 Southwind Owner and Internet Remote since 1999

D. Kemp wrote:

>Make sure all body parts are grounded to the frame;
>hood, doors, engine block (should already have a
>braided ground strap), body (bond sections together),
>and especially the exhaust pipe. The exhaust can act
>as an antenna if it's not grounded to the frame.
>Disassemble and clean and reassemble all ground

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