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  #1 (permalink)  
Old 02-17-2017, 9:26 AM
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Default Ferrite Filters

Does one of these anywhere on a CB wiring help with spark plug noise? If not, is there anything? This happens to be on a motorcycle so not much out there in the way of anything to begin with these days for two wheelers.

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Old 02-17-2017, 11:08 AM
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Try running the radio off a separate battery (not connected to anything on the vehicle, just the radio) and see if that makes the noise go away. If so, a filter like https://www.amazon.com/WORKMAN-NF-40...dp/B00IJZWWWM/ is your best bet, not a ferrite choke.

If that doesn't make the noise go away, it's coming in through the antenna, and the only fix is to eliminate the noise at the source. Do not put filters on the antenna. A filter on the antenna will reduce noise and signal level equally, and you'll be worse off than doing nothing. The proper fix will depend on exactly what is causing the noise.
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Old 02-17-2017, 3:34 PM
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Well since the radio is on a motorcycle it's very hard to get separate power with another battery and still go down the road. I'm almost positive it's spark plug noise. I'll still look at your suggestion though. But what little I know I suspect the true solution is to try different plugs or plug wires. Was hoping a collar like that would solve it but there is never an easy fix. Thanks.
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Old 02-17-2017, 3:47 PM
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Quote:
Originally Posted by jonwienke View Post
Try running the radio off a separate battery (not connected to anything on the vehicle, just the radio) and see if that makes the noise go away. If so, a filter like https://www.amazon.com/WORKMAN-NF-40...dp/B00IJZWWWM/ is your best bet, not a ferrite choke.

If that doesn't make the noise go away, it's coming in through the antenna, and the only fix is to eliminate the noise at the source. Do not put filters on the antenna. A filter on the antenna will reduce noise and signal level equally, and you'll be worse off than doing nothing. The proper fix will depend on exactly what is causing the noise.
Hmmm, looking at your suggestion, it looks like that goes in between the battery and radio. Is that correct? That might be well worth it to do anyway. The bikes I have CBs on both have what they call canbus systems that are very picky about any outside electrical noise from what I understand. Difference being my noise is audio and the canbus doesn't like any kind of extra electrical load. So not at all sure how it would all play out. It's all so confusing to me. What I have works. I'm just getting like static that's too repetitive to be random pulses of any kind.
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Old 02-17-2017, 8:39 PM
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ferrite chokes won't work on spark noise

its being picked up by the antenna and coax

that's why FM is superior to am radio

radios with noise blankers tend to help but you likely will get better results using resistor plugs and shielded plug wires

aircraft radios are also am so they are prone to spark plug noise as well

they use ignition shielding braid over plug wires to reduce noise
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Old 02-17-2017, 9:06 PM
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Quote:
Originally Posted by hogcowboy View Post
Hmmm, looking at your suggestion, it looks like that goes in between the battery and radio. Is that correct?
That is correct. It filters the DC power going to the radio.

The easiest way to test would be to borrow a spare battery and connect it to the radio. The bike doesn't necessarily have to be moving, just running. If the noise goes away with the alternate power source connected, then the filter will help. if not, you'll have to look elsewhere, and solving things will be more difficult.
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Old 02-18-2017, 5:18 PM
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cowbay,
It can take some sleuthing. The noise can be EMI, electromagnetic interference, that is traveling in the electrical system of the bike, in the wires. Or it can be RFI, radio frequency interference, in which case it is being broadcast through the air around the bike.

EMI you can filter out, one way or another. RFI you can't filter out, you have to find out what the source is, and change something in the source.

With cars using spark plugs, changing from "performance" spark plug cables and plugs, to "resistor" cables and plugs can eliminate a lot of noise at the source, IF the problem is the wires and plugs. No real difference in performance, that's all been standard equipment for ages now.

It might be worth asking a dealer (since there are so many helmet radios, etc. out now) or a mobile radio shop if they could just listen to the noise on your radio, and recognize what it is.
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Old 02-18-2017, 5:33 PM
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I suspect plugs because it does change with RPMs up to a point where it just seems to be constant. Or at such a rate I can't tell the difference. I think the first thing I'm going to try is a change of plugs since they are easy enough to change and try ones that have resistors or whatever the R rated once are. Changing the plug wires isn't as easy. That's looks like a fuel tank lift which I've never done. I was so hoping some little widget would help. No free lunch once again. Never fails with me.
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Old 02-18-2017, 6:30 PM
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Have you even tried the snap around ferrite 'filters' on your spark plug wires?

Look for information on shielding spark plugs on the Corvette.
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Old 02-18-2017, 6:38 PM
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Quote:
Originally Posted by cmdrwill View Post
Have you even tried the snap around ferrite 'filters' on your spark plug wires?

Look for information on shielding spark plugs on the Corvette.
Well that was actually what I was wondering about. I didn't and the reason I made the thread. I just had no idea if it would be worth trying or not. Or if it did work, for how long. Would the excess heat in the area cause it to stop working if it did work to start with. So the answer to the question is no, I haven't actually tried it. Are you saying it might actually work? The cost of the things might be worth a try I guess.
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Old 02-18-2017, 9:00 PM
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Speaking of plug wires, if you have solid-core wires (or wires with Litz wire cores) they last a very long time. If you have or switch to resistor wires, you may find a new wire has a resistance (end to end) of 500 ohms. As it ages, that can go up to 5000 then 50000 ohms. Somewhere between those two, it is time for new wires. (Old wires never quite die, they just work poorly.) So pulling the fuel tank and replacing the wires, or at least finding out more specifics about them, might not be a bad idea. If they are resistor wires, they may already be shot.
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Old 02-19-2017, 6:06 AM
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Quote:
Originally Posted by Rred View Post
Speaking of plug wires, if you have solid-core wires (or wires with Litz wire cores) they last a very long time. If you have or switch to resistor wires, you may find a new wire has a resistance (end to end) of 500 ohms. As it ages, that can go up to 5000 then 50000 ohms. Somewhere between those two, it is time for new wires. (Old wires never quite die, they just work poorly.) So pulling the fuel tank and replacing the wires, or at least finding out more specifics about them, might not be a bad idea. If they are resistor wires, they may already be shot.
I think you are probably correct. May as well do it and eliminate that as a potential.
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Old 02-19-2017, 5:51 PM
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ferrite is for RF only

it will NOT work on 40kv DC spark

if you have spark plug noise, it was discovered when the very first am radio appeared in a car that resistor plug wires and resistor plugs got rid of the noise
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Old 02-20-2017, 4:21 AM
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Quote:
Originally Posted by MOTEX View Post
ferrite is for RF only

it will NOT work on 40kv DC spark

if you have spark plug noise, it was discovered when the very first am radio appeared in a car that resistor plug wires and resistor plugs got rid of the noise
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Old 02-20-2017, 11:06 AM
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Woa, hold your check mark there cowboy. The interference generated by the spark plug IS RF and the spark plug wires are antennas that radiate the RF and ferrite on the spark plug wires will have an effect on reducing the noise. It may not be practical but it will snuff out noise to the CB radio if done right.

First you have to look at the equipment making the noise. The rise and or fall time of the spark determines what range of frequencies with a 1 microsecond rise time making RF noise up to the 1MHz range, a 100 nanosecond rise time making up to 10MHz of noise, a 10 nanosecond rise time up to 100MHz and 1 nanosecond rise time up to 1GHz. The rise time of the motorcycle ignition system is at least at least a 38 nanosecond to reach the CB band to cause and radiate lots of noise there.

The intensity of the spark partially determines the level of interference and the length of exposed spark plug wires and how they are shielded by vehicle body parts have a huge impact on how far away the noise is picked up and what frequency range is most affected. Motorcycles usually have very short spark plug wires that favor higher frequencies above CB but they are out in the open with little to shield them.

The most common snap on ferrite cores out there are a #43 mix and clamping that over a spark plug wire equates to only 1 turn through the core providing very little choking effect at CB frequencies. Every time you run the wire through a ferrite core the inductance goes up by 4X, or about the same as using 4 snap on ferrites in series. I know from experience it takes at least 3 turns through a #43 mix ferrite clamp on to have a good effect at reducing RF noise in the VHF band (150MHz) but still does very little at CB frequencies.

If you were to get a ferrite clamp on with a more appropriate mix at CB frequencies like a #31, then installing about 20 of these over the spark plug wires would have a very noticeable effect on reducing the spark plug noise and possibly up to about 20dB of reduction, which is similar to store bought 1:1 balun chokes made for coax. Or wrapping about 4 or 5 turns of spark plug wire through one #31 mix ferrite would work about the same.

The problems are now, will all this ferrite fit on my spark plug wires and what is this going to do to the spark? There will be some degradation of the spark but probably no more than going to resistor type wiring or plugs. The resistor wires or plugs slow down the rise time of the spark and intensity among other things and contribute to reducing the radiated noise.

In the end if it is the spark plugs making all the noise in the CB, and there are resistor plugs or wires already in use and they are in good shape, the only real practical way to reduce the noise would be to shield the spark plug wires with hollow braid over the entire run of exposed wire. This works really well but in some cases the added capacitance of the ignition system output to ground will delay the spark enough to require adjusting the timing a little. Not a big deal and on the few vehicles I've done this on the engine performance did not appear to be affected.

Bottom line of my post here is spark plug noise is RF and ferrite will have an effect on reducing it if you can accommodate the ferrite. Hope the OP can run some tests and determine exactly what is causing the noise so the proper fix can be done.
prcguy

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Last edited by prcguy; 02-20-2017 at 11:15 AM..
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