DF'ing a noise source.

[Ed/KB1HYS]

Ok, I've been having problems with something in the nieghborhood creating an S-9 + buzz.  not from my house, I've taken a drive around with the radio in the truck up at the top of the am band between stations and found the strongest location.

I have a scanner that will pick up the aviation band (VHF AM)  with a whip antenna.  I've been trying to use the whip as a "pointer" but I seem to be doing something wrong.

I thought a vertical whip had a null off the tip, so that I would hear a sig then a null then the sig again as I swept past the noise source. 

There is a BNC connection for an external antenna on the back of the scanner, should I build a loop or some kind of 2m yagi?

[K1JJ]

Ed,

I have the same set up as you. First I drive around using the AM BC band and then use an aircraft AM receiver when close by. I built a little 4 el Yagi for the job.   I wud make it a 3el if I did it again to fit better into the vehicle..

I once DFed to a spot one mile away  -with 3 phase wires that looked like a concentration camp and walked the area with the Yagi to find the offending insulators. The problem was getting the power company off their ass. They finally dismantled the camp - it went out of biz, so all set.

The Yagi is the way to go. You can stand 40' from the pole and acutally hear the noise rise and fall as you point from the pole bottom to top.   Vert and horiz rotation helps too.

BTW, make sure the Yagi is tuned close to the freq you are receiving (or vice versa) or you will have a rotatable dipole instead. (Tune both parasitic els and driven el)   Using a standard Yagi software program will be close enuff. 

T

[KB2WIG]

E
Try using a paper clip 'jammed' into the bnc. If too much signal, you can clip/break off part of the clip. Use your hand to obtain the famous "shaded paper clip" antenna.  Your mileage may vary.

klc

[KD6VXI]

Ok, I've been having problems with something in the nieghborhood creating an S-9 + buzz.  not from my house, I've taken a drive around with the radio in the truck up at the top of the am band between stations and found the strongest location.

Myself and a bunch of other amateurs in the area have found that the 'digital ballasts' the farmers use on their marijuana crops WREAK HAVOC EVERYWHERE.

I can't listen from the AM broadcash band to 6 meters at my house.  My neighbor has a bunch of the digital ballasts   .99 pf I can see why they are getting away from magnetics!

What's REALLY funny is this:  My Yeasu gets TRASHED.  I can plug a DECENT CB radio (SSB Cobra 148), and I get NO NOISE.....  Would this tend to be AC coupled?  The Cobra is known for being one of the best with DC filtering.....

BUT, a nice trashy waveform that takes out from near DC to daylight is typically these digital grow light ballasts.

--Shane

[k4kyv]

What we really need is for the FeeCee to get off their ass, formulate some realistic Part 15 interference standards, and enforce them.

Why should hams be so paranoid about talking 10 minutes and 15 seconds between ID's or running occasional voice peaks a few watts over the limit, if the FeeCee won't even do anything about widespread harmful interference from unlicensed sources?

Don't even get me started. 

[K5UJ]

FCC has been so unbelievably underfunded and in my opinion not by accident because you see, they regulate an industry both communications and manufacturing where a lot of money is made and ahem, certain administrations over the past 30 or 40 years have not been all that wild about regulation of industry when that industry is raking in mountains of cash.   
We have the best government regulation money can buy.

But, one quick RF noise point--if your prob. is due to street lights (the sodium vapor ones are particularly prone to RFI) i.e. the noise starts up at dusk and suddenly vanishes when the lights go off, then your AM airband rx won't help because that's one noise that kills the low HF and 160 but does not extend up into VHF. 

Rob

[Ed/KB1HYS]

I can hear it during the day (I was out driving around this morning).  I can hear it on the Airband too during the day so I know I'm close.

If it wasn't so dang cold now...

[KA2QFX]

Ed,
   If you're into building an accurate DFing loop here's one I built. It's very sharp and works well enough to define noise sources within a few feet of each other.

The design parameters are very flexible, but this one tunes from b'dcst band to about 4MHz.  It's 13 turns of wire with a 1000pF variable cap in series, about 14" on each side.  The coupling loop to the receiver is two turns of #20 AWG magnet wire but any wire would do. This two turn loop feeds the low side of a small 4:1 bifilar balun on a type 47 ferrite bead. The high side goes to the BNC for the receiver.  The balun is critical or the pattern will be so screwed up as to be useless.

I've no comment on whose responsible or what to do once you find the source but wish you good luck.

[N0WVA]

What we really need is for the FeeCee to get off their ass, formulate some realistic Part 15 interference standards, and enforce them.

Why should hams be so paranoid about talking 10 minutes and 15 seconds between ID's or running occasional voice peaks a few watts over the limit, if the FeeCee won't even do anything about widespread harmful interference from unlicensed sources?

Don't even get me started. 

Currently FCC's job is to totally trash the spectrum for analog users, then shove digital down everyones throats as salvation. I dont expect them to do much about powerline noise when they fully endorse such widespread jamming as IBOC.

[N0WVA]

Ive found powerline interference by using a pocket SW receiver. By walking the powerline and shortening the antenna till I cant hear the noise, then the closer I get, the noise starts to break through. Ive also used an AM receiver with a good loopstick and have found that one needs to position himself back away from the powerline if possible to triangulate. Sometimes thelines radiate all over the place and the farther you get from them, the easier it is to get a "null" in the right direction.

[Pete, WA2CWA]

I suspect some people believe the FCC works on the "action by osmosis" principle. If you find the source, document as much as you can, record the interference, and file a complaint with the FCC.
Further info is here:
http://www.fcc.gov/eb/AmaCmpl.html
Here are some FCC actions in 2009 in regards to interference complaints:
http://www.fcc.gov/eb/AmateurActions/Welcome.html