I have an Alpine AM/FM/CD unit in my truck. On the AM, and ONLY on the AM,
I get static. Now, I am old enough to remember when a small capacitor on
the generator (they used to be called generators) caused this problem. It
is not as loud as the old type hum, but goes up and down with RPM. It is
also worse when I have my truck rack on the truck. At low RPM, I can hear
the radio, but at high RPM, I just get static. FM works with NO static at
any time. Anyone here had the same problem? Any quick fixes or magic
bullets?

Steve

Probable bum antenna or bad alternator.

Remove the fan belt and see if the noise goes away.

Also leaky plug wires can also cause mischief. Usually visible at night.

--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
they come up with this striped stuff.
"SteveB" wrote in message
news:_XLGc.11018$nc.6501@fed1read03...
I have an Alpine AM/FM/CD unit in my truck. On the AM, and ONLY on the
AM,
I get static. Now, I am old enough to remember when a small capacitor on
the generator (they used to be called generators) caused this problem. It
is not as loud as the old type hum, but goes up and down with RPM. It is
also worse when I have my truck rack on the truck. At low RPM, I can hear
the radio, but at high RPM, I just get static. FM works with NO static at
any time. Anyone here had the same problem? Any quick fixes or magic
bullets?

Steve

"SteveB" wrote in message
news:_XLGc.11018$nc.6501@fed1read03...
I have an Alpine AM/FM/CD unit in my truck. On the AM, and ONLY on the
AM,
I get static. Now, I am old enough to remember when a small capacitor on
the generator (they used to be called generators) caused this problem. It
is not as loud as the old type hum, but goes up and down with RPM. It is
also worse when I have my truck rack on the truck. At low RPM, I can hear
the radio, but at high RPM, I just get static. FM works with NO static at
any time. Anyone here had the same problem? Any quick fixes or magic
bullets?

Steve



An alternator will cause a continuous whine to be heard through the
speakers, varying with RPM. A capacitor across the +ve output terminal and
ground can sometimes cure this. The greatest cause of interference on AM
bands in my experience is poor grounding of the aerial to the vehicle body,
a non-continuous aerial co-ax cable, or a problem with the radio itself.
The static type interference is usually from the ignition system or other
motor that runs continuously, such as a fuel pump.

HTH

Anthony
Remove eight from email to reply.

Is the tip of your antenna intact? If you have a sharp end, you can get
noise. The solution I've heard is to put a tennis ball on the end (or
something similar). I haven't tried this...

Steve Smith

SteveB wrote:

I have an Alpine AM/FM/CD unit in my truck. On the AM, and ONLY on the AM,
I get static. Now, I am old enough to remember when a small capacitor on
the generator (they used to be called generators) caused this problem. It
is not as loud as the old type hum, but goes up and down with RPM. It is
also worse when I have my truck rack on the truck. At low RPM, I can hear
the radio, but at high RPM, I just get static. FM works with NO static at
any time. Anyone here had the same problem? Any quick fixes or magic
bullets?

Steve

"SteveB" wrote in message news:_XLGc.11018$nc.6501@fed1read03...
I have an Alpine AM/FM/CD unit in my truck. On the AM, and ONLY on the AM,
I get static. Now, I am old enough to remember when a small capacitor on
the generator (they used to be called generators) caused this problem. It
is not as loud as the old type hum, but goes up and down with RPM. It is
also worse when I have my truck rack on the truck. At low RPM, I can hear
the radio, but at high RPM, I just get static. FM works with NO static at
any time. Anyone here had the same problem? Any quick fixes or magic
bullets?

If it were coming in the DC lines, it would be there in the FM also.
FM being noise limiting by virtue if the modulation system itself,
(Noise pulses clipped and eliminated, only frequency variations
causing an output) static is clipped and eliminated before the audio
stages. If it were coming in the DC, you'd hear it on FM also. This
leaves the antenna, and the problem of deciding where it's being
generated. Antenna cable, as has been mentioned, is a place to start,
But where it's being generated and how to eliminate it can be
frustrating. Putting the rack on may be causing some blanking of the
antenna, cutting the signal input, and making the static seem worse.
Any ground cables that are loose or corroded can cause it, they're not
the cause, but don't eliminate the static as they should. A bad
ground shield on the antenna plug can be another, anything that goes
to ground can allow the static to be radiated rather than grounded if
the connection is not good, and at low voltages, the degree of which
it has to be bad can be very small. Check anything that's supposed to
be grounded, but no guarantees there either. Chasing static is pretty
much of a crap shoot.

If the sound is more a tick tick sound rather than a humming type static,
the problem is the ign. system. Fresh wires and plugs may fix or relieve
the problem a bit but it will probably still be there. If the sound is a
humming type then the alternator is probably at fault and attaching a
condensor to the output of the alternator at the alternator should decrease
that a lot.
AM radio is a lot more suceptible to noise as it is an amplitude modulated
system and thus any noise tends to sound like the signal.

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works every time it is tried!

I have an Alpine AM/FM/CD unit in my truck. On the AM, and ONLY on the AM,
I get static. Now, I am old enough to remember when a small capacitor on
the generator (they used to be called generators) caused this problem. It
is not as loud as the old type hum, but goes up and down with RPM. It is
also worse when I have my truck rack on the truck. At low RPM, I can hear
the radio, but at high RPM, I just get static. FM works with NO static at
any time. Anyone here had the same problem? Any quick fixes or magic
bullets?

Steve


As already mentioned - there should be a capacitor (from the factory)
somewhere around the distributor (don't know what kind of vehicle you
have) or the ignition block feeding the spark plug wires. The cap may
have bad connections itself, or simply need replaced. It won't hurt
to add a few caps here and there (like on the heater fan motor, etc),
but also look for a little scraper type deal from the inner fender or
the firewall which is supposed to "scratch" the underside of the hood
everytime it's closed - makes the hood part of the rest of the body
metal. It may be a flexible copper wire braid strap bolted to both,
but look for it, clean it up and make sure it's tight.
HTH
Ken.

"Bob May" wrote in message
...
If the sound is more a tick tick sound rather than a humming type static,
the problem is the ign. system. Fresh wires and plugs may fix or relieve
the problem a bit but it will probably still be there. If the sound is a
humming type then the alternator is probably at fault and attaching a
condensor to the output of the alternator at the alternator should
decrease
that a lot.
AM radio is a lot more suceptible to noise as it is an amplitude modulated
system and thus any noise tends to sound like the signal.

--
Bob May

Yup. Definitely a tick tick rather than a melodious hum. Will look at the
wires at night. Been a good while since a tune up, too. Since it could use
a tune up, am going go have that done, and then see if it persists. I take
the rack on and off, but would like to have it work at all times.

Steve

SteveB wrote:

I have an Alpine AM/FM/CD unit in my truck. On the AM, and ONLY on the AM,
I get static. Now, I am old enough to remember when a small capacitor on
the generator (they used to be called generators) caused this problem. It
is not as loud as the old type hum, but goes up and down with RPM. It is
also worse when I have my truck rack on the truck. At low RPM, I can hear
the radio, but at high RPM, I just get static. FM works with NO static at
any time. Anyone here had the same problem? Any quick fixes or magic
bullets?

Steve


Might be time to have the points changed and the CAP across them replaced.
These drive the HV coil that fluxes and generates HV for the plugs.

Traditional trouble maker - the cap drys out. Or gets burnt out.

Martin

--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder