Pages: [1]   Go Down

Author Topic: 125kHz Noise finding  (Read 1935 times)

AE8RS

  • Member
  • Posts: 59
125kHz Noise finding
« on: January 02, 2019, 01:05:44 PM »

We're experiencing some RF interference at work and I thought it might be a fun exercise in tracking down noise. The only problem is it's interfering with 125kHz RFID tags, so things start to get a bit unwieldy. Does anyone have clever antennas that fit inside that one could use to do some direction finding?
Logged

WB4SPT

  • Member
  • Posts: 917
RE: 125kHz Noise finding
« Reply #1 on: January 02, 2019, 01:38:13 PM »

I would predict a ferrite loopstick in your future.   ;D

Winding and tuning a coil of wire on a ferrite with high perm;  maybe a 1 foot rod of mix 76 or 78?  
Bi-directional pattern of course.  
« Last Edit: January 02, 2019, 01:41:13 PM by WB4SPT »
Logged

KD0REQ

  • Member
  • Posts: 2644
RE: 125kHz Noise finding
« Reply #2 on: January 02, 2019, 02:27:03 PM »

I guess a parabolic antenna is out :-D

unless you mount a ferrite rod inside an old satellite TV dish on a slide to hopefully shield the back pickup
Logged

NC5P

  • Member
  • Posts: 66
RE: 125kHz Noise finding
« Reply #3 on: January 03, 2019, 05:40:48 PM »

Conducted emissions below 150 kHz are not limited under Part 15.  That is prime territory for switching power supplies and lighting drivers to operate.  Most noise problems at that frequency are conducted, at least that's how it gets out of the offending equipment.  The result can then either go directly into your equipment via the power cord or couple inductively or electrically through the air from AC wiring.  That makes it difficult to track down like VHF radiation using antennas because it can seem to come from every direction.  Start by disconnecting anything with a switching power supply, including led or fluorescent light fixtures.  Use circuit breakers if need be to turn things off.  Then re-connect things until the noise comes back.  If there is still noise than it may be coming from outside the building.  If you are in an industrial setting you will need to coordinate this when shutting things off will not impact work schedules, like weekends or late. 
Logged
Pages: [1]   Go Up