GMCforum: GMCnet » AM radio reception, any ideas how to improve?

Home » Public Forums » GMCnet » AM radio reception, any ideas how to improve?

Show: Today's Messages :: Polls :: Message Navigator

AM radio reception, any ideas how to improve? [message #337721]

Tue, 09 October 2018 08:41

Scott Nutter

Messages: 782
Registered: January 2015
Location: Houston/San Diego

Karma: 4

Senior Member

With the ignition on I get fairly good AM reception.
With the engine started my reception is terrible.

I believe I have resister type plugs and run Springfield plug wires.
But, my FM reception is good.......

Any ideas on how to improve my AM reception(besides going to satellite radio)!
Thanks, Scott.

Scott Nutter 1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final drive, Quad bags, Dave Lenzi super duty mid axle disc brakes, tankless water heater, everything Lenzi. Alex Ferrera installed MSD Atomic EFI Houston, Texas

Report message to a moderator

Re: AM radio reception, any ideas how to improve? [message #337723 is a reply to message #337721]

Tue, 09 October 2018 09:39

RF_Burns

Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

If your AM reception is good with the engine OFF and poor when the engine is running, you have whats called "Site Noise" Its akin to you standing by a big diesel engine talking to someone and hearing them with no problem. Then the Diesel starts and you can no longer hear them. Something in the your coache's engine (likely ignition) is creating RF noise and drowning out the AM signal. Could also be the heater fan etc. FM does not get bothered by such RF noise as much as AM band.

The only way to fix it is find the source of the noise and suppress it.

There use to be a small trimmer capacitor for tuning the vehicle antenna on AM, but I haven't seen those in years.

I spent a lot of time in my career tracking down site noise interference on public safety radio systems. There is a lot more sources of RF noise now than in the past.

Good luck on your quest for the source.

Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

Report message to a moderator

Re: AM radio reception, any ideas how to improve? [message #337725 is a reply to message #337721]

Tue, 09 October 2018 09:57

Scott Nutter

Messages: 782
Registered: January 2015
Location: Houston/San Diego

Karma: 4

Senior Member

Thanks Bruce,
Sounds like a lot of work. Any chance that a magnetic base antenna mounted further aft would help at all? Or is there just too much interference coming through the power leads? Or would running a power lead from the house batteries bypass the engine interference?
Scott.

Scott Nutter 1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final drive, Quad bags, Dave Lenzi super duty mid axle disc brakes, tankless water heater, everything Lenzi. Alex Ferrera installed MSD Atomic EFI Houston, Texas

Report message to a moderator

Re: [GMCnet] AM radio reception, any ideas how to improve? [message #337729 is a reply to message #337725]

Tue, 09 October 2018 10:39

Richard Denney

Messages: 920
Registered: April 2010

Karma: 9

Senior Member

Depends on the noise, but probably none of those things will do much.

A clean ground is necessary, but if the noise is from RF emissions from
devices, then the problem isn’t the power line. Moving the antenna may
help, but the long lead may receive more noise.

AM is a noise magnet—any RF at all will affect it, especially with the
broadbanded antennas we have to use (the AM band covers over an octave of
spectrum—filtering tightly would kill much of the band). You have to
identify the source.

Is it a ticking sound? That can be a leaky spark plug wire or the
distributor. Is it an RPM-related whine? That could be the alternator. Does
the generator affect it? That could be the generator, or the converter. As
Bruce said, it could be any electric motor that runs with the ignition.

If the noise is gone when the ignition is on but the engine is not running,
it’s probably not one of those electric motors. If it’s noisy only when the
engine is running, try jumping the engine block to the aluminum body (the
edge of the hatch will do)—if the noise changes, then maybe it’s the ground
between the engine and the chassis, or between the chassis and the body.
Don’t run another ground—that could make it worse. Clean up and verify the
correct grounds.

We used to use portable transistor radios, tuned between AM stations, to
find noise. Those are hard to find any more.

Rick “like detective work” Denney

On Tue, Oct 9, 2018 at 10:58 AM Scott Nutter wrote:

> Thanks Bruce,
> Sounds like a lot of work. Any chance that a magnetic base antenna mounted
> further aft would help at all? Or is there just too much interference
> coming through the power leads? Or would running a power lead from the
> house batteries bypass the engine interference?
> Scott.
> --
> Scott Nutter
> 1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final
> drive, Quad bags, tankless water heater, everything Lenzi. Alex Ferrera
> installed MSD Atomic EFI
> Houston, Texas
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Rick Denney
73 x-Glacier 230 "Jaws"
Off-list email to rick at rickdenney dot com
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

Report message to a moderator

Re: [GMCnet] AM radio reception, any ideas how to improve? [message #337730 is a reply to message #337729]

Tue, 09 October 2018 11:19

tphipps

Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL

Karma: 9

Senior Member

You might try wrapping the power lead around a ferrite core. Helps to absorb RF travelling on the power leads. Difficult to stop random noise on AM radios. FM is a different animal.

If the noise level changes with the engine increasing and decreasing in rpm, it is generally ignition related. A whine sound should be alternator. Good grounds are your friend.

Find stuff you like on FM. LOL

Tom

2012 Phoenix Cruiser model 2552 KA4CSG

Report message to a moderator

Re: AM radio reception, any ideas how to improve? [message #337731 is a reply to message #337721]

Tue, 09 October 2018 11:32

bwevers

Messages: 598
Registered: October 2010
Location: San Jose

Karma: 5

Senior Member

Another possibility is the ignition condenser, in the distributor is old and has lost its capacitance.

Bill Wevers GMC49ers, GMC Western States 1975 Glenbrook - Manny Powerdrive, OneTon 455 F Block, G heads San Jose

Report message to a moderator

Re: AM radio reception, any ideas how to improve? [message #337732 is a reply to message #337721]

Tue, 09 October 2018 11:37

bwevers

Messages: 598
Registered: October 2010
Location: San Jose

Karma: 5

Senior Member

Also, the GND shield on the coax from the antenna should be chassis GNDed.
Maybe the antenna lead has failed (the one that goes from the roof down the middle
of the windshield). There's a connection above the drivers compartment that might
be loose or corroded.

Bill Wevers GMC49ers, GMC Western States 1975 Glenbrook - Manny Powerdrive, OneTon 455 F Block, G heads San Jose

Report message to a moderator

Re: AM radio reception, any ideas how to improve? [message #337734 is a reply to message #337721]

Tue, 09 October 2018 12:12

GatsbysCruise

Messages: 261
Registered: January 2017
Location: Waukegan, Illinois

Karma: 3

Senior Member

I had a noise that was coming from alternator whine.
Engine off, radio good. Engine running, whine.

NOTE: This type of interference is being transmitted to your antenna, which
then sends this noise to the radio.

I was looking everywhere for an answer, even had the alternator checked out as recommended.
Found nothing wrong with the alternator.

Grounds checked good, and I even double grounded things.

I finally found a hint to the problem in a Ham magazine.
They were talking about harmonics, and noises created from the ALTERNATOR.

You need a filter to clean this noise up.
A tell tale that this might be the problem is when you rev the engine up, you hear the sound freq go up.
It is a high pitch sound, not low pitch like ignition noise.

The fix was to take some #10 wire and wind in a circle, about 1 to 1 1.5 inch diameter. About
10 turns should do it.

Now you need some #14, or #16 wire, and wrap around the coil you just made with #10 wire.
You will wrap, through the center of the coil, around the side, through the center,
around the coil, etc etc. You want to go around the loop. It doesn't have to be a tight
winding , but you are trying to stop this RF from emanating out of the coil.

You will disconnect the Alternator positive and connect one end of the #10 wire to the alternator
positive. The other end of the #10 wire connects to the original Positive wire.

Connect BOTH ends of the wire that wraps around that coil to ground.

That will stop any RF that is transmitted from the Alternator positive cable.

You could try just wrapping a coil about 6 inches long, around the existing positive cable, (no coil on the pos
cable) just wrap the wire around the single positive cable, and grounding the wire that is wrapped around the Positive cable. I just followed
the suggestion to coil both cables.

This will only cure noise from the Alternator Pos cable. ( the high whine when engine running )

slc
Gatsbys' Cruiser
74 Glacier 260

GatsbysCruise. \ 74GMC260 Former Glacier Model style. \ Waukegan, Illinois \ Keep those MiniDiscs Spinning \ MY GREYHOUND IS FASTER THAN YOUR HONOR ROLL STUDENT \ WindowsXP-Win7-Win8.1-UBUNTU STUDIO - UBUNTU VOYAGER - Berzin Auto Center

[Updated on: Tue, 09 October 2018 12:19]

Report message to a moderator

Re: AM radio reception, any ideas how to improve? [message #337735 is a reply to message #337721]

Tue, 09 October 2018 13:52

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

The most common thing that causes that is a poor GROUND CONNECTION at the base of the antenna where it mounts at the roof. This is more common on a GMC because the antenna is mounted in aluminum rather than steel. Take it apart up there, clean up everything including the inside of the hole in the roof. Reassemble using anti-oxidation grease and see what you have. After finishing unplug the antenna at the radio and measure the resistance between the shield and the body of the coach. The body is NOT the instrument panel which is grounded to the engine. The resistance should be very near ZERO.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

Report message to a moderator

Re: [GMCnet] AM radio reception, any ideas how to improve? [message #337737 is a reply to message #337735]

Tue, 09 October 2018 16:02

James Hupy

Messages: 6806
Registered: May 2010

Karma: -62

Senior Member

Are you complaining about the poor performance of your AM radio receiver or
the program content of the AM radio station? In our area, your choice is
either Christian message or Mariachi or talk? radio on the AM band.

On Tue, Oct 9, 2018, 12:24 PM Ken Burton wrote:

> The most common thing that causes that is a poor GROUND CONNECTION at the
> base of the antenna where it mounts at the roof. This is more common on a
> GMC because the antenna is mounted in aluminum rather than steel. Take it
> apart up there, clean up everything including the inside of the hole in the
> roof. Reassemble using anti-oxidation grease and see what you have.
> After finishing unplug the antenna at the radio and measure the resistance
> between the shield and the body of the coach. The body is NOT the
> instrument panel which is grounded to the engine. The resistance should be
> very
> near ZERO.
>
>
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

Report message to a moderator

Re: [GMCnet] AM radio reception, any ideas how to improve? [message #337740 is a reply to message #337737]

Tue, 09 October 2018 18:12

mghamms

Messages: 466
Registered: March 2016
Location: Ware, Massachusetts

Karma: 2

Senior Member

google:
radio 12v line filter
It may help.

1977 Kingsley 455 as stock as it gets except lots of Ragusa parts

Report message to a moderator

Re: AM radio reception, any ideas how to improve? [message #337744 is a reply to message #337721]

Tue, 09 October 2018 22:19

Scott Nutter

Messages: 782
Registered: January 2015
Location: Houston/San Diego

Karma: 4

Senior Member

Ok, thanks all......
I will be calling 1-800-satelite radio.
All I really want to do is listen to Rush or Shawn while traveling. Preferably in English.....
Scott.

Scott Nutter 1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final drive, Quad bags, Dave Lenzi super duty mid axle disc brakes, tankless water heater, everything Lenzi. Alex Ferrera installed MSD Atomic EFI Houston, Texas

Report message to a moderator

Re: [GMCnet] AM radio reception, any ideas how to improve? [message #337746 is a reply to message #337744]

Tue, 09 October 2018 22:22

Sammy Williams

Messages: 522
Registered: August 2010

Karma: -2

Senior Member

www.siriusxn.com :)

Sammy Williams

On Tue, Oct 9, 2018, 22:20 Scott Nutter wrote:

> Ok, thanks all......
> I will be calling 1-800-satelite radio.
> All I really want to do is listen to Rush or Shawn while traveling.
> Preferably in English.....
> Scott.
> --
> Scott Nutter
> 1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final
> drive, Quad bags, tankless water heater, everything Lenzi. Alex Ferrera
> installed MSD Atomic EFI
> Houston, Texas
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

Report message to a moderator

Re: [GMCnet] AM radio reception, any ideas how to improve? [message #337747 is a reply to message #337729]

Tue, 09 October 2018 22:22

Sammy Williams

Messages: 522
Registered: August 2010

Karma: -2

Senior Member

www.siriusxm.com autocorrect Greer
Sammy Williams

On Tue, Oct 9, 2018, 22:22 Sammy Williams wrote:

> www.siriusxn.com :)
>
> Sammy Williams
>
> On Tue, Oct 9, 2018, 22:20 Scott Nutter wrote:
>
>> Ok, thanks all......
>> I will be calling 1-800-satelite radio.
>> All I really want to do is listen to Rush or Shawn while traveling.
>> Preferably in English.....
>> Scott.
>> --
>> Scott Nutter
>> 1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21
>> final drive, Quad bags, tankless water heater, everything Lenzi. Alex
>> Ferrera
>> installed MSD Atomic EFI
>> Houston, Texas
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

Report message to a moderator

Re: AM radio reception, any ideas how to improve? [message #337749 is a reply to message #337744]

Tue, 09 October 2018 23:47

Bullitthead

Messages: 1411
Registered: November 2013

Karma: 5

Senior Member

Further diagnosis: Get a known good antenna and substitute it first to see if it makes a difference or completely corrects the problem. Then you will know if the problem is in the incoming signal or inside the radio itself, possibly riding in on the power supply and ground. If it makes a difference, do what Ken Burton posted...most likely cause. Did dozens of antenna replacements at the stereo shop due to the failed ground at the antenna base from corrosion and/or the plug end losing the ground (shield) connection.

Terry Kelpien ASE Master Technician 73 Glacier 260 Smithfield, Va.

Report message to a moderator

Re: AM radio reception, any ideas how to improve? [message #337754 is a reply to message #337721]

Wed, 10 October 2018 08:55

JohnL455

Messages: 4447
Registered: October 2006
Location: Woodstock, IL

Karma: 12

Senior Member

Please describe the noise or noises and how they change with engine RPM. My guess is corroded connections (green or white oxides). If water enters at top the coax can act as a "hose" and rot things at the radio end and in between. Deoxit D5 spray is your friend.

John Lebetski
Woodstock, IL
77 Eleganza II

Report message to a moderator

Re: AM radio reception, any ideas how to improve? [message #337768 is a reply to message #337721]

Wed, 10 October 2018 13:34

bwevers

Messages: 598
Registered: October 2010
Location: San Jose

Karma: 5

Senior Member

Another noise source in my rig is the power converter/charger
I can clearly hear 50KW stations from 150 miles away when
I unplug the Progressive Dynamics charger. The ignition
makes some AM noise with the motor running, but not much.

I have a Sony receiver and replaced the whip antenna in the roof.

Bill Wevers GMC49ers, GMC Western States 1975 Glenbrook - Manny Powerdrive, OneTon 455 F Block, G heads San Jose

Report message to a moderator

Previous Topic:	1973 Canyonlands Awning
Next Topic:	New Timer trip report

Goto Forum:

-=] Back to Top [=-

Current Time: Mon Mar 10 02:47:07 CDT 2025

Total time taken to generate the page: 0.00955 seconds