Radio / intercom noise

[Gearhead]

Hey Y'all,

 

I've had a persistent problem with engine rpm-related noise in the radio and intercom, both thru the speakers and headsets. I've posted here and there on the subject. I had the noise improve a little when I improved the grounding on the bike. But it was still significant.

 

Well, I just pretty much fixed it. The factory has 3 noise-reducing capacitors installed: two in the radio noise filter (one for system hot, the other for battery back-up (hot all the time)), and the third near the voltage regulator. Each cap goes from hot to ground and bleeds off noise (AC signal) but doesn't short out the DC power. They say caps dry out and don't work as well as they age. Well, mine are 22 years old!

 

So I went to Radio Shack and bought two 2200 microfarad caps and one 4400. I then bought two more 2200's after I nearly blew one up and ruined them by wiring them in backward and then yanked them out when I heard the gurgling - live and learn :-) I put the 4400 near the regulator and the 2200's at the radio near the existing noise filter, and wired them as I said, from hot to ground. The noise is nearly gone - not completely, but I wonder if the remaining noise could be normal as it's very small. Certain things increase it, as they did before, but on a lower level:

• Setting the Headphone Attenuator on the handlebar at Max gives a little noise that almost goes away if I set it on the big dot just below Max.
  
• The Auto Volume circuit introduces noise. If I have it all the way down it goes away, and it increases steadily as I turn this feature more sensitive.
  
• There's a slight hiss in the system even with the engine off - just par for the course I guess.
  
• If I crank the Auto Volume and the Headphone Attenuator both up to Max, the noise is still less than what I had before with much more conservative settings.
  
• As long as music is playing, I cannot hear the noise at all. In totally quiet times and with the knobs set to contain the noise, I still can't hear it unless I'm REALLY trying.
  

I'm very pleased, been waiting 3 years to do this! The caps are about 5 bucks each, whether you fry them or not! Very good solution. Thanks to GeorgeS for suggesting it!

 

Jeremy

[GeorgeS]

Glad to hear it worked !! Also, going thru all the main ground connections is a good thing to do, for many other reasons.

 

One other thought. If the remaining static, or noise is in the high frequency range of the Audio Spectrum. Then, changing Earphones, that have Less responce to the higher frequencies, might help some. But, as to which brand, I would not know.