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Author Topic: Nasty RFI Spectrum Pattern  (Read 2947 times)
KG6Q
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Posts: 58




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« on: August 30, 2014, 11:13:39 AM »

Using HRD's DM780 waterfall as a cheap ham's spectrum analyzer, I see the below RFI pattern on all HF bands through 6m with my Yaesu FT-897d mode set to AM. The signal strength ranges from S6 to about +5db on 30 and 40m. This RFI practically eliminates QSOs except for strong JT65 signals that can cut through this noise  Huh



It appears to be narrow-band modulation spikes at a 60Hz rate. The RFI disappears when I disconnect my radio antenna.The narrow-band pattern leads me to believe it is NOT power-line arcing which I have had trouble with in past.

Any ideas how to track this down?
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WA2ISE
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Posts: 158




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« Reply #1 on: August 30, 2014, 02:06:02 PM »

Does it also get into the AM broadcast band?  If it does, you could use a portable AM transistor radio to sniff around the neighborhood.  If you can get a null by pointing the ferrite rod antenna towards the source, see if you can triangulate with more nulls at other locations in the neighborhood.  Problem is that if it's a bad powerline insulator arcing to ground, the lines can act line longwire antennas and confuse the triangulation.  I'd expect harmonics at 120Hz, as the voltage reaches a peak and a negative peak twice every 60Hz waveform.
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ZENKI
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Posts: 956




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« Reply #2 on: August 30, 2014, 06:15:58 PM »

Always turn everything off in your own house.

Unplug every walwart and  especially things like cell phone, ipad and any other gadget chargers.

PC's and amplified  speakers and their associated power supplies are well known QRM sources.

Also check your routers and associated power supplies, Linksys power supplies are notorious QRM generators. None of their power supplies are EMC compliant.
Incredible that such a large company as them could get away with breaking EMC laws.

LED lighting is another source of QRM. LED downlighting and light dimmer can be horrific jammers. Cheap fluorescent electronic starters and ballasts can cause massive problems. The cheap junk that comes in from china is the main source of this crud.

Car battery chargers and inverter switchmode chargers and alarm float chargers are another source of annoying birdies

Looking at that spectrum display I would say its a switchmode power supply from a cell phone or cheap TV. The carrier levels look very strong.

Anyway clean your house first making sure the source is not insider before working on the neighbors houses.
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