Ferrite Filters

An alchemy of sparks, copper wire and earth

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maxstu
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Ferrite Filters

Post by maxstu »

Reckon there is a few good & knowlegdeable members l can rely on to answer this one...
Raymarine C120 marine chartplotter is interferring with a ST4000 depth sounder. I tested this by running each piece of equipment solo and then together, with same results every time. Depth finder loses reading for about 20 seconds when plottter is running. Yet absolutely fine without plotter running.
Could it be their respective cables running to fuse system overlaying or nearby each other causing the problem? Ive read the C120 chartplotter is very (electronically) noisy and a ferrite fuse may solve this issue?
What options do l have to resolve interference?
Regards
Stuart
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Mocki
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Re: Ferrite Filters

Post by Mocki »

Ferrite rings need at least 3 turns of the cable around and through to be effective, the snap on filter type also need you to feed through at least twice to have a decent effect

You need to establish if it’s harmonic , cable borne or air borne

Double shielding will help, copper tape wrapped around the cables helps , and of course don’t run cables paralleled
Steve
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maxstu
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Re: Ferrite Filters

Post by maxstu »

Mocki wrote:Ferrite rings need at least 3 turns of the cable around and through to be effective, the snap on filter type also need you to feed through at least twice to have a decent effect

You need to establish if it’s harmonic , cable borne or air borne

Double shielding will help, copper tape wrapped around the cables helps , and of course don’t run cables paralleled

Good one Steve and thanks.
Recalling to when l fed cables through headlining, l suspect both equipment cables ended side by side before going to their appropriate fuses in the control system. Will remove headlining next week and have a peep.
Copper tape? Never heard of that! Will tinfoil do instead :D
Thanks
Stuart
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Re: Ferrite Filters

Post by Mocki »

Steve
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Re: Ferrite Filters

Post by itchyfeet »

I have 20K of EMC test equipment at work ( and thats a cheap one) and I spend alot of time trying to solve EMC issues. Its not easy even with the proper kit to analyse you can see the noise but reducing it is a bit of a black art. Often if you reduce it in one area you just move the energy elsewhere.
Without out any kit you are pissing in the wind IMO.
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Re: Ferrite Filters

Post by itchyfeet »

Mocki wrote:
Double shielding will help, copper tape wrapped around the cables helps , and of course don’t run cables paralleled


its true separation and shielding of cables may help but only if they are not already shielded cables and it depends on frequency.

you can also buy metal braided sleeve which is more expensive than tape but will give better coverage.
https://uk.rs-online.com/web/p/cable-sleeves/8372441/" onclick="window.open(this.href);return false;

If you look at bead ferrites they quote attenuation at 25Mhz and 100 that's because they don't work well at frequencies lower than this so it may help but not with low frequncy noise which tends to be conducted.

Are these mains based kit or DC based and what are the cables? power of data?
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Re: Ferrite Filters

Post by maxstu »

Cheers both,
Will post again tomorrow :ok
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Re: Ferrite Filters

Post by maxstu »

itchyfeet wrote: Without out any kit you are pissing in the wind IMO.
Yes l tend to spend a lot of time doing above :D
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Re: Ferrite Filters

Post by bigbadbob76 »

I've not seen that particular problem before but have had VHFs and sounders block the plotter before.
Worth checking if the plotter is causing a supply voltage drop to the sounder, and checking that you have no dirty connections to both items. salty sea air causes no end of connection problems as I'm sure you know.
Keeping the sounder transducer cabling well away from the plotter wiring will help.
Do you have an AIS transponder connected to, or built into, the plotter? if so it's transmissions could interfere with the sounder. check the antenna wiring for the AIS if you have it.
Does it only happen as you power up the plotter or is it every so often while the plotter is on?

And just maybe you have an NMEA connection between the sounder and the plotter, try unplugging it if you do as it can cause an earth loop.
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Re: Ferrite Filters

Post by maxstu »

[quote="itchyfeet"]

Are these mains based kit or DC based and what are the cables? power of data?

Answer is..Not sure. Its my sisters yacht. Im good with deck items. Warps lines halyards sails and rigging etc. No good with electronics. I was hoping this would a plug and play upgrade. I had to upgrade power line for plotter. It was an over the counter item. NOS Raymarine so appropriate

12volt power for plotter connected to radar overlay and data for transducer l should imagine.
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Re: Ferrite Filters

Post by maxstu »

bigbadbob76 wrote:I've not seen that particular problem before but have had VHFs and sounders block the plotter before.
Worth checking if the plotter is causing a supply voltage drop to the sounder, and checking that you have no dirty connections to both items. salty sea air causes no end of connection problems as I'm sure you know.
Keeping the sounder transducer cabling well away from the plotter wiring will help.
Do you have an AIS transponder connected to, or built into, the plotter? if so it's transmissions could interfere with the sounder. check the antenna wiring for the AIS if you have it.
Does it only happen as you power up the plotter or is it every so often while the plotter is on?

And just maybe you have an NMEA connection between the sounder and the plotter, try unplugging it if you do as it can cause an earth loop.


Hi Bob,
Good to hear from you.
Hopefully will visit yacht next week as its on the hard at present for anodes and antifoul.
Reading through your excellent response to my mayday l will take it step by step.
I believe AIS is built in but not operational. Depth works perfectly. Then power up chartplotter and depth loses reading for about 20-30 seconds and repeats this error every few minutes or so. Power down plotter and depth stabilises. Transducer is clean as a whistle and tested.
Firstly cable routing. The plotter is independently sited above wheel binnacle. Whereas smaller nav equip wind, depth and long/lat are above main hatch. Yet all cables end up above roof lining in main salon before heading to fuse panel on port side.
Will start there first.
Many thanks
Stuart
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Re: Ferrite Filters

Post by bigbadbob76 »

Hi Stu.
Glad to help if I can.
Unfortunately it's a bit of a crystal ball problem.

maxstu wrote: plotter connected to radar overlay and data for transducer l should imagine.

If plotter IS connected to radar and Sounder (they often are) you could well have an earth loop problem, try disconnecting the plotter from everything else and re-connecting one at a time.

maxstu wrote:depth loses reading for about 20-30 seconds and repeats this error every few minutes or so....I believe AIS is built in but not operational.

This every few minutes period makes me think AIS. ;-)
If AIS is transmitting but has no antenna attached or has a dodgy antenna or poor earthing this will definitely cause problems. assuming it's a class B AIS, which it usually is on a yacht, it will transmit at 2W every 3 minutes when stationary and every 30s when moving. worth checking that AIS transmissions ARE disabled.
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maxstu
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Re: Ferrite Filters

Post by maxstu »

bigbadbob76 wrote:Hi Stu.
Glad to help if I can.
Unfortunately it's a bit of a crystal ball problem.

maxstu wrote: plotter connected to radar overlay and data for transducer l should imagine.

If plotter IS connected to radar and Sounder (they often are) you could well have an earth loop problem, try disconnecting the plotter from everything else and re-connecting one at a time.

maxstu wrote:depth loses reading for about 20-30 seconds and repeats this error every few minutes or so....I believe AIS is built in but not operational.

This every few minutes period makes me think AIS. ;-)
If AIS is transmitting but has no antenna attached or has a dodgy antenna or poor earthing this will definitely cause problems. assuming it's a class B AIS, which it usually is on a yacht, it will transmit at 2W every 3 minutes when stationary and every 30s when moving. worth checking that AIS transmissions ARE disabled.
Great suggestions Bob, No antenna for AIS. Surely must be class B as only 10 metre yacht
Will delve into Plotter settings and take a look.
Thank
Stuart
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Re: Ferrite Filters

Post by bigbadbob76 »

Just had a look at the specs for the plotter. raymarine C120 is an older unit that doesn't have built in AIS.
C120W is a newer unit. is this the one you have?
specs say-
"AIS Suppport- Support for class B AIS- Supports silent mode"
You want to find silent mode and turn it on. ;-)
Or remove power from external AIS transponder. it is not built in but may be connected to the plotter and controlled by it.

from the manual-
10.7 AIS silent mode
AIS silent mode enables you to disable AIS transmissions
AIS silent mode enables you to disable the transmitting functions
of your AIS equipment. This is useful when you do not want to
transmit your vessel’s AIS data to other AIS receivers, but still wish
to receive data from other vessels.
Note: Not all AIS equipment supports silent mode. For more
information, refer to the documentation that accompanies your
AIS unit.
Enabling and disabling AIS silent mode
In the chart or radar application:
1. Press the MENU button.
2. Using the trackpad, highlight the AIS Layer Setup menu item,
then press the trackpad right to select it.
3. Using the trackpad, highlight the Silent Mode option, then press
the trackpad right to select it.
4. Using the trackpad, select the ON option to enable silent mode,
or OFF to disable it.



I've been trying to think why else a plotter would interfere with a sounder every few minutes and I'm struggling, hmmm....
The other way around I could understand as the sounder has a high output power.
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