Dave,
>From what you have said two mechanisms come to mind.
This could be tire static. As the rubber rolls along the road it develops a
charge which discharges and forms a static noise. This is unlikely with stock
tires as they are specified to have enough internal resistance so as to drain
off this charge as it forms.
A more likely culprit would be the Antilock Braking System (ABS) and its wheel
sensors. These sensors detect wheel motion and employ the ABS when the wheels
are not all rotating at the same speed.
There are 3 of these sensors: one on each of the front wheels and a third
monitoring the rear axle. These sensors receive siganling from the ABS module
so it could also be part of the problem.
Earl N5TU
To: <rfi@contesting.com>
Date: Fri, 21 Mar 2003 20:20:37 -0500
From: David Jordan <wa3gin@erols.com>
To: "rfi@contesting.com" <rfi@contesting.com>
Subject: [RFI] Unknown RFI from truck when in motion but in neutral
Message-ID: <3E7BBA65.4020702@erols.com>
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Hi Folks,
Found an interesting problem while listening to AM 630 all news station
here in WDC.
Getting loud clicking noise. Sounds very much like spark plug noise but
when coasting at 30mph and placing the engine in neutral such that the
engine RPM drops from 2500rpm to idle, the ticking noise remains at
speed. However, as the vehicle slows down the noise also slows down. I
can rev up the engine while it remains in neutral but the speed of the
noise doesn't change. Is there some type of speed or other monitoring
devices on the wheels of the 2001 Explorer that is sending RF signals to
the on-board computer? This one is got me scratching my head.
thoughts,
dave
wa3gin
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To: <rfi@contesting.com>
Date: Fri, 21 Mar 2003 22:22:17 -0800
From: Jim Smith <jimsmith@shaw.ca>
To: "rfi@contesting.com" <rfi@contesting.com>
Subject: Re: [RFI] Unknown RFI from truck when in motion but in neutral
Message-ID: <3E7C0119.2040800@shaw.ca>
References: <3E7BBA65.4020702@erols.com>
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Hmm.... I may be way off base here but I seem to recall from 35 years
ago that hams would squirt graphite powder into the interior of their
tires to eliminate noise produced by a mechanism that I no longer
recall. Maybe an urban myth. No doubt others can give better info.
FWIW de Jim Smith VE7FO
------------------------------
Earl Morse
EMC Engineering
Bldg 5, Cube 2E104
Phone: 313.323.7968
Fax: 313.390.5327
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