Shorepower and RFI

[rachapman]

In various places, Calais being the most recent, when we connect to the shore power post the radio goes crazy. So much noise on AM that its unusable. No access to TMS!
The RFI is present when the shorepower lead is connected at the post but not the boat, but disappears when the lead is connected to boat but not the post.

The shorepower connects to a RCD, then spurs around the boat.

So it seems the lead is acting as an aerial?

Any ideas regarding how to reduce the RFI?

 

[Gunfleet]

ferrite rings is the place to start. http://www.maplin.co.uk/free_uk_delivery/Ferrite_Rings_29788/Ferrite_Rings_29788.htm
dead cheap too.

 

[rachapman]

So are we talking about making a loop through a ferrite ring at the 'post' end of the lead?

 

[rachapman]

Just looked at the Maplins site. Can't tell you how much I appreciate such a cheap solution! Seems to me the cost of the tape to swathe it all in will be the most expensive part.

 

[Gunfleet]

You'll probably be able to find marinized ones for £10 each if you look round the chandleries.

 

[pollygonforty]

subsequent question on RFI Ihave ongoing problem with short wave radio reception when fridge compressor kicks in radio becomes totally inaudible ,Any solutions?

 

[Gunfleet]

Ferrite beads? Explanation on

http://en.wikipedia.org/wiki/Ferrite_bead

http://www.bytemark.com/products/ferbead.htm

purchase at http://www.rapidonline.com/searchresults.aspx?style=0&kw=ferrite

you can easily construct a little meter to track down the source. There's a description of how on

http://www.ifwtech.co.uk/g3sek/clip-on/clip-on.htm

 

[Guest]

The simple solution is to turn off the fridge. Ferrites work for power line noise and noise picked up by the power lines, but they do not help transmitted noise. Since you are radiating a great deal of energy it is good practice to shut down all non-essential systems. To give an example. If the boat next door to you in an marina is noisy you can hear their systems even with no common power connection.

The ferrites are used mainly to protect sensitive systems like modems/instruments from the Tx power. Our boat used to read 50 knots of wind whenever Tx on 4MHz.