Radio Interference (RFI)

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I am a Radio Ham (K7EZ) and really enjoy quiet reception from my Cummins dielsel while mobiling. I re-located the antenna recently and noticed a new noise on RX when the engine is running. There is a TSB out for RFI and I just called my local dealer only to find out the filter cost $395! WOW! I think the filter is for the 24 valve ISB as it goes in series with the fuel pump/fuel pump module.

Has anyone else got suggestions, I can't run my antenna on the rear bumper where it used to be because I tow a 5th wheel.



'73 and Keep on Rammin

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'98 12V 3500 Dually Std Cab, Auto, 3. 54, Banks Stinger Plus, Sun Coast TC. BD valve body, BD Pressureloc

 

[Archive]

Hi Roger. de kf7is. I guess I lucked-out because, I have no noise at all (at least on 40 mtrs... . I havn't tried the other bands. I'm using an Icom 735 and a hustler 40 mtr resonator mounted in the passanger side rear-most stake-hole. I will check-out the vhf rig tomorrow. BTW, the icom just rests on the rear seat. 73

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Jim... ... KF7IS
'99 Cummins w/Dodge QC, SB, 5sp, 4X4 Loaded, 265/75 BFGs on 16/8 AR 5 Spoke Chrome Wheels, Xenon Flares,Chrome Stepbar, Rhino Guard, Amethyst Pearl... just git'in started

 

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I too have a 12-valve (97) and have a Yaesu FT-2500 mounted on the dash. The antenna is mounted on the driver's fender using a bracket that slips between hood and fender. The antenna is a Larsen 1/2 wave tuned for about 150 MHz, to cover both ham and fire frequencies.
I have no noise on RX, but the truck sometimes makes a strange noise on TX! The brake warning light comes on also during TX.
I believe I have cable radiation due to a loose connection, since I did not solder the braid to the PL-259 connector on the cable.
Does your noise vary in pitch with engine speed? If so check the alternator, it may need suppression.
KD7GZQ

 

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I use a FT-100 and the noise is on 40 meters. It is about 10 db of steady white noise when the engine is running no variation on speed. I use a screwdriver ant and it was quiet on all bands when mounted on the rear bumper. Seems that moving it closer to the engine compartment/cab makes it pick up the noise.

I was shocked at the RFI filter price from DC. What is in that box? a couple of caps and perhaps a choke, gimme a break.

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'98 12V 3500 Dually Std Cab, Auto, 3. 54, Banks Stinger Plus, Sun Coast TC. BD valve body, BD Pressureloc

 

[Archive]

40 meters is about 7 MHz. It is quite likely that is the clock frequency of a micro-computer. The only micro-computer in a 12-valve truck is in the PCM. It would be interesting to make a small loop antenna for a 40m radio and hold the loop near the PCM to see if the noise gets louder as you approach the PCM. A spectrum analyzer works best but those are expensive.
If indeed it is the PCM, you could try bypassing the power pins with 0. 1uF. You can probably add 100pF to every logic pin without hurting its performance.
Let me know what you find.
KD7GZQ

 

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Thanks for the thread on Rx noise. I am not a HAM, but pulled an old CB out of retirement and was quite surprised at the noise I heard when I fired it up in the RAM. I was thinking "wow this CB is trashed, no spark plugs and it still sounds awful"...

I'll try the antenna on the rear bumper (if I can find the CB at the bottom of the trash can) :< )

 

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I Run an Alinco DX70 HF at 100 watts into a four position Dawia coax switch, into four Hamstik antennas:10, 17, 20, 40 meters, and carry 6 and 15 meter hamsticks in the bed of the truck. I also have a Yaesu Ft 8000R, 2m-440 rig, at 50 watts, with a mag mount antenna. I use the 20 amp power point plug and have absolutely no noise at all. Both transceivers are grounded to a bolt under the drivers seat. My Elmer has an identical rig in his new Dodge Cummins diesel and also has no noise. Try the power point connection for your power source, or go directly to one of your batteries. (0ne may be quieter). Ground everything!! Hope this helps. Sam KF6GUW- Amateur extra

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1999 Dodge Laramie SLT QC, 24V Cummins turbo diesel ISB, 2WD, auto trans, 3. 55 rear end- LSD, long bed, HD towing and camper pkg,K&N air filter, Boost and Pyro gauge combo, CD player, trip computer,electric seats, bright white paint, chrome diamond plate tool box, resonator removed, turbo silencer ring removed, all options except leather seats, Full UHF-VHF and HF transceiver equipped (KF6GUW) "I love the smell of diesel in the morning. "
Hemet, California

 

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I have a direct ground and also #10 for both + and - direct to batt # 2. I notice that DC bonded to the bed to chassis for ground nicely. I had to do it myself for old chebbie truck. I am beginning to think I need to bond the cab better. Can't find a place where it has a good connection to the chassis. I also know that bonding the hood will help.

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'98 12V 3500 Dually Std Cab, Auto, 3. 54, Banks Stinger Plus, Sun Coast TC. BD valve body, BD Pressureloc