[RFI] 97 Chevy Tahoe noise problem

[Michael Neverdosky]

It sounds to me like the fuel injector pulses.
You can check with the dealer for factory fixes. You can also shield the
wires to the fuel injectors and the computer.

michael N6CHV

Scott Neader KA9FOX wrote:
> 
> Hey guys!  I have an ICOM IC706-MKiiG installed in my 1997 Chevy Tahoe,
> with a Hi-Q-Antennas 3/80 mounted to the towing hitch.  System works very
> well, except some nasty engine noise.  I have put up with the noise thus
> far by using the excellent Noise Blanker on the IC-706.  However, there is
> a penalty for using the Noise Blanker... loud signals that are within
> 10-25Khz of the frequency cause a lot racket.  So, I'd like to fix the
> problem, if possible.
> 
> To help determine the source of the noise, I hooked up a separate battery
> to my rig, so that it had no connections to the car power, and the noise
> did not change at all.  Also, I would not describe it as "clean audio
> whine".  More of a low rumbly sound that increases in pitch with engine
> speed.  In other words, I don't think it's the alternator.
> 
> I have created a 60 second WAV file of the noise... it is about 1.2mb.  The
> file is here:  http://www.qth.com/ka9fox/noise.wav.  This file was created
> with the radio being powered by the external battery, with the radio tuned
> to about 14.200.  As I remember it, the noise seems to be heard equally on
> all bands, but if it is important to analyze the noise as it relates to
> frequency, let me know.
> 
> What you are hearing on this sound file is:
> 
> -- 00 seconds to 05 seconds:  engine off and the key turned off.
> 
> -- 05 seconds to 10 seconds:  engine off, but with the key turned on.  I'm
> told that fuel pump noise would appear here, if that were the problem.
> 
> -- 12 seconds to 13 seconds:  car is started.
> 
> -- 13 seconds to 23 seconds:  engine idle speed.  Noise is about S7 (NB
> disabled).
> 
> -- 23 seconds to 52 seconds:  engine being revved up, then back to idle, a
> few times.
> 
> -- 52 seconds to end of sound clip:  car is turned off.
> 
> I have not made any attempts to cure the noise yet.  Some have suggested
> installing a Radio Shack 12v filter near the battery.  Others have
> suggested RFI surpressing spark plug cables, such as those from
> http://www.magnecor.com.  And others have suggested bonding all the body
> parts together with copper straps.  I'm pretty handy with a computer, but
> when it comes to cars... well, it's not my bag.  So, my question is...
> before I put in the big effort to implement these suggestions.. .are any of
> them likely to help this particular noise problem?  Anyone out there have a
> Chevy truck in the 1997 era that have had similar noise problems, that have
> been solved?  If so, what seemed to do the trick?
> 
> Thanks in advance!
>