AM Radio noise

[gcw206]

When I bought my 1969 280SL, it had an aftermarket stereo system installed.  Fortunately, the PO did not cut the dash, so it was not difficult to R/R the head unit and all of the assorted pieces.  I sourced a restored OE Becker Europa (w/iPod adapter), and a Hirschmann automatic antenna.  I also replaced the speakers (the holes were already cut) with 4 each Focal speakers, coupled to a small Alpine KTP 445U auxiliary amplifier.  The system works great on both FM and the iPod input channels, but on AM I notice a "ticking" sound that varies with the engine RPM.  (AM is fine with the engine off.)  I have installed resistor spark plugs, a condenser on the LT side of the coil, a Stinger SGN 21 antenna filter, and a Bandit Stereo Noise Filter on each of the hot leads to the Alpine amplifier, and to the Becker head unit.  The hood has the spring grounding device installed at the hood latch, the antenna is grounded, and the engine block and the transmission both have ground cables.  I have removed and cleaned the connections on all of the ground wires that I can think of.  On AM, I still get some ticking noise when the engine is running.  I realize that this is 50 YO technology, but I would still like a cleaner AM output.  What have I not done?

[scoot]

If you had have said that the interference was on the MP3 input I would tell you that you need a stereo cable between phone and head unit that had a filter.  But on AM?  I'm pretty stumped.  I assume you have no interference or ticking when the car is off and the radio is on....?

[gcw206]

Yes, that is right.  No engine no noise, then no ticking noise; and when the engine is running the tick increases with the engine speed (with all other electrical items are off, save the fuel pump).  Fairly "sure:" it is ignition related, and probably on the LT side?  This is driving me nuts.

[Benz Dr.]

I listen to Rush on FM and maybe you listen to a different Rush on AM which is likely where all that static and noise is coming from.

[Tyler S]

Is it a consitant ticking noise or is the pattern random? If its random it may be somthing mechanical that is making and breaking contact intermittently. This may be a longshot but try disconnecting the tachometer cable at the engine block near the distributer then retest. When my blaupunkt was installed in my car it would make weird ticks untill by chance I disconnected the cable and it stopped. I think the routing so close to the dist and ign wires has something to do with it. Transfering interference into the dash. A new cable did fix the issue.

[Rolf-Dieter ✝︎]

I never use my radio, after all it’s the 21st century ... I use my iPot and a nice blue color match Wireless JAM BOX ... no noises of any kind

Check it out ——> http://mashable.com/2012/10/31/jawbone-big-jambox/#Cpban65nrqqS

Dieter

[fosdicke]

Disconnect the Alt. Belt and try it .
A dirty ignition coil wire ,Distributor cap corrosion inside or out also could be causing the Static.

[gcw206]

I was told that all threads should be finished, so here goes....................
After weeks of trial and error, I finally came to the conclusion that AM reception with my stock factory Becker radio and Hirschmann antenna just was not going to work to my satisfaction.
Now, I route both AM and FM radio transmissions through my i Phone, and then into the Becker head.  Same stations, just a different delivery system. It works great!  Very clear and sharp!
Thanks for all of the assistance; this is truly a great site.