[AMRadio] RE:Telephone Wiring RFI Treatment

W4AWM at aol.com W4AWM at aol.com
Sun Dec 17 14:39:23 EST 2006

Hi Mike,

The hum on your phone line is most likely caused by a ground somewhere in the 
system.  If you have revently installed wiring, there should be a test jack 
where the lines come in from outside.  Disconnect the plastic plyg from this 
jack which isolates your inside telephone wiring.  Plug a separate phone into 
this jack and listen.  If the hum is there, the problem is outside your home and 
you shoule call the phone company for service. 

If it disappears, the problem is inside your house.  If you are paying for 
inside wiring service which you shoule be able to detirmnine from your bill, the 
phone company service will fix it for free. If you are not paying for 
service, you will have to find it yourself or pay the price to the phone company to 
find the problem for you which is not exactly cheap.

If you want to find it yourself, oner thing to check is the wall outlets.  
Remove them from the wall and determine if there is a greenish blue oxide on the 
connector. This sometimes happens when the connector gets damp from 
condensation or a leak in the insulation somewhere. If you find this problem, do not 
bother trying to clean the connector. The problem will return soon.  It is 
better to just replace it with a new one.

As far as RFI, there is a very good filter sold by an outfit that advertises 
in QST.  They are expensive and you will probably need one for each phone, bit 
my experience is that they will solve most problems.  

You can also go the ferrite bead route on the leads behind the wall or try 
with one of the larger ferrite units that snaps apart and you then wrap several 
turns of the cable from the wall to the phone around it and snap it closed. 
This also work in some instances and are far cheaper that the filters I first 

Good luck and let us know what you find.

73 and Top of the Season to you,

John,  W4AWM

More information about the AMRadio mailing list

This page last updated 17 Dec 2017.