Ignition noise in mobile operation - RFI Forum at eHam.net

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eHam.net Forum : RFI : Ignition noise in mobile operation

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Ignition noise in mobile operation	Reply
by KD5YDY on October 21, 2003	Mail this to a friend!
Occasionally our radio club runs a public service project involving ham radio communications. We are put in as riders in somebodyelse's car and are supposed to operate mobile (via cig lighter or other connection and a mag mount). I won't run 50 watts through a cig lighter so take along my OPTIMA Blue Top for 12v DC. Unfortunately, I pick up ignition noise with this setup. Is there a way I can suppress engine noise in a less than optimal, temporary mobile setting? Would ferrite beads on the cables help eliminate interfering engine noise? Open to any solutions that doesn't require modification to vehicle.

RE: Ignition noise in mobile operation	Reply
by WB2WIK on October 22, 2003	Mail this to a friend!
What band are you talking about? Do you actually get ignition noise on VHF-FM signals? Or do you mean HF-SSB? Ignition noise has to be pretty radical to make it past an FM detector... WB2WIK/6

RE: Ignition noise in mobile operation	Reply
by KD5YDY on October 22, 2003	Mail this to a friend!
I've experienced it on all bands (HF is worst) but the ones we use most are 2m and 440 band. It's a buzzing background noise that increases in pitch as the vehicle accelerates and decreases as the vehicle slows down. It sounds exactly like what I used to hear when I ran an unfiltered cable from cig lighter to HT or when my rig was near a power generator in an RV. My system is not connected to the vehicles electrical or battery system in any way. Should I be grounding my rig to the vehicle chassis? There must be something I'm not doing right. KD5YDY

RE: Ignition noise in mobile operation	Reply
by FRANKM12 on October 29, 2003	Mail this to a friend!
KD5YDY, I haven't heard about this one since people ran copper plug wires. You don't have copper plug wires do you? Try cleaning your battery posts. 73 frank KG4VLQ

RE: Ignition noise in mobile operation	Reply
by AC2RC on November 7, 2003	Mail this to a friend!
Grounding the radio and battery to the vehicle might help, that's what I do with my HF rig.

RE: Ignition noise in mobile operation	Reply
by K1CJS on March 16, 2004	Mail this to a friend!
That noise could be something other than ignition noise. It could also be alternator whine or possibly fuel pump noise. As far as your rig being isolated from the vehicle, what kind of antenna are you using? A magmount is capacitively coupled to the vehicle. Any antenna will pick up RF interference if it is close enough to the source. Anyway, my guess is alternator whine. As far as getting rid of it, there is not too much you can do without getting into the vehicle electrical system. The best thing is to use fully shielded co-ax and locate the antenna on the roof as far from the alternator as you can. It is also possible the alternator could be close to failure. If the brushes are worn, the alternator will start to cause excessive RF noise. Good luck and 73!

RE: Ignition noise in mobile operation	Reply
by K1CJS on March 16, 2004	Mail this to a friend!
That noise could be something other than ignition noise. It could also be alternator whine or possibly fuel pump noise. As far as your rig being isolated from the vehicle, what kind of antenna are you using? A magmount is capacitively coupled to the vehicle. Any antenna will pick up RF interference if it is close enough to the source. Anyway, my guess is alternator whine. As far as getting rid of it, there is not too much you can do without getting into the vehicle electrical system. The best thing is to use fully shielded co-ax and locate the antenna on the roof as far from the alternator as you can. It is also possible the alternator could be close to failure. If the brushes are worn, the alternator will start to cause excessive RF noise. Good luck and 73!

RE: Ignition noise in mobile operation	Reply
by N5TU on April 1, 2004	Mail this to a friend!
It would be almost (never say never) impossible to make a setup that could be moved from vehicle to vehicle and be immune to interference. Your best bet is to be careful of antenna placement. Choose an area that is quiet by moving your mag mount and being aware of possible noise sources. The rear decklid is a good place but stay away from the exhaust as it could radiated ignition noise from the engine. Stay away from the rear window as there are usually noisy vehicle modules there that could be an issue. Modules are hidden through out the car, in the pillars, under the seats, in the fuel tank etc that can interfere with radios. The one thing you can do is make a brute force filter for you DC input to the radio. This will filter out all noise coming into the radio through the power line, which can be especially noisy if you get it from the cigarette lighter. You can ensure clean power but antenna placement is going to be the only solution (be it somewhat limited) for your radiated interference. N5TU

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