Radio Interference Issue Solved

[antennaclimber]

Finally figured out an RF hash/noise interference signal that was wiping out my 11 meter and HF radios. Definitely RF related, sometimes it's there and other times its not. The M1008 and M1009 are having the same issue. I'm wondering "How on earth does a mechanical diesel engine make so much RF noise?"

On the M1008: Changed alternator, added capacitor to the alternator B+ line, added ground straps to the hood, fenders, engine and fire wall. No success with the noise suppression radios are almost deaf.Finally noticed that the noise came and went during the glow plug warm up time, hmmm, unplugged GP card. No success, noise still there. Then I noticed that it came and went when the low coolant light was on, unplugged low coolant circuit board and the noise went away, radios were working well! Cleaned the contacts on the board reinstalled it and the noise was still there.

So for now the board will remain out so the radios will be able to receive. Now on to the M1009 to see if it is the same source of RF interference.

 

[Sharecropper]

Finally figured out an RF hash/noise interference signal that was wiping out my 11 meter and HF radios. Definitely RF related, sometimes it's there and other times its not. The M1008 and M1009 are having the same issue. I'm wondering "How on earth does a mechanical diesel engine make so much RF noise?"

On the M1008: Changed alternator, added capacitor to the alternator B+ line, added ground straps to the hood, fenders, engine and fire wall. No success with the noise suppression radios are almost deaf.Finally noticed that the noise came and went during the glow plug warm up time, hmmm, unplugged GP card. No success, noise still there. Then I noticed that it came and went when the low coolant light was on, unplugged low coolant circuit board and the noise went away, radios were working well! Cleaned the contacts on the board reinstalled it and the noise was still there.

So for now the board will remain out so the radios will be able to receive. Now on to the M1009 to see if it is the same source of RF interference.

Is that low coolant circuit (idiot light) really necessary if a cab water temperature gauge is installed? Like yourself I plan on multiple radios in the future and would like to eliminate all RF noise.

Thanks for the discovery.

 

[antennaclimber]

I would say that a temp gauge is much better than an idiot light.

Keeping an eye on any temps above the normal operating range is a good way to make sure the cooling system is functioning properly. As you are well know, gauges are your friend to help solve minor issues before they become bigger ones.

 

[Sharecropper]

I would say that a temp gauge is much better than an idiot light.

Keeping an eye on any temps above the normal operating range is a good way to make sure the cooling system is functioning properly. As you are well know, gauges are your friend to help solve minor issues before they become bigger ones.

Thanks. Can you post the procedure for eliminating the low coolant circuit? I'm not sure I know where that circuit board is located.

 

[antennaclimber]

Thanks. Can you post the procedure for eliminating the low coolant circuit? I'm not sure I know where that circuit board is located.

I just pulled the card out to ensure that the noise was emanating from the card. As time permits, I may change out a few of the parts and see if that helps any.

My card was up near the parking brake mechanism to the left of the fuse block. It's in a black plastic holder.

 

[MarcusOReallyus]

I'm interested in hearing what you find, AC. I'm trying to think what that board could be doing that would make a lot of noise. I would think it would be a pretty simple circuit. Voltage doubler, maybe?

 

[Farmitall]

Good find!

Now try putting some snap on ferrite beads on the wires going to the card and see if it suppresses the noise. Add as many as it takes.

Thats the problem with 11m radios, they are AM/SSB and prone to both atmospheric and man made noise. FM tranceivers are much less and in most instances, immune.

 

[antennaclimber]

I'm interested in hearing what you find, AC. I'm trying to think what that board could be doing that would make a lot of noise. I would think it would be a pretty simple circuit. Voltage doubler, maybe?

No sure what that board does. I will look into it as time permits.

Its spring and everyone wants tower and antenna work done. We are still finishing up jobs from last year!

 

[MarcusOReallyus]

Get up there and get that 5G installed!