Working with s7 -s9 noise

Started by N1KTJ, May 07, 2016, 05:56:50 am

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Am going to post this discussion on multiple forums in hope to get more thinking about this

How does a beginner work with s7 to s9 constant HF noise levels?  Living in an apartment that is what I see always. 
There is no way to put up a large antenna outside, and even if I had that there is no guaranty that transmission/reception would work. 

My only break through has been jt65 and some CW.  Hoping this can be discussed more to reduce hobby frustration for beginners on the HF bands.

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May 07, 2016, 06:55:13 pm #2 Last Edit: May 07, 2016, 07:05:41 pm by Quietguy
Quote from: N1KTJ on May 07, 2016, 05:56:50 amHow does a beginner work with s7 to s9 constant HF noise levels?  Living in an apartment that is what I see always. 

Have you tried to find out where the noise is coming from?  Maybe a significant amount is coming from inside your own apartment.  Shut down everything electrical you have control over and see if the noise level changes.  If it does, try to isolate the various sources.  Lamp dimmers and switch mode power supplies (like the lightweight wall warts) are notorious for generating noise.  We have one dimmer in a bedroom wall switch box that makes HF almost unusable across the hall but the noise goes away when turned off.  If noise is coming in from outside on 120 volt power lines you can install line filters to help knock it down.  It's a process of elimination but sometimes you can make significant improvements just within your own stuff even though you can't get rid of it all.

Edit to add:  Other common sources to check are 120 volt LED replacements for standard light bulbs and all types of fluorescent lights - both older style tubes and the newer compact fluorescent energy savers.  These all use power supplies that can be incredibly noisy.



Great advise Wally. I should have taken the time to formulate a better answer, but a magnetic loop is the first thing I thought about, assuming the source of the noise could not be found. "Wall warts" are notorious noise makers. Houses are full of cheap RF producing electronics these days..



The mag loop is a good suggestion Gil.  I need to dig my mag loop out of the box in the basement and try it.  When I throw the main breaker on my house the S-8 noise drops to S-1, but turning on individual breakers I've identified about 6 breakers that bring the noise floor up to beyond S-6.  It seems like I've got about 20 things to fix.  I swear, if a contest ever comes along that I care about, I'm throwing the main breaker and running off a car battery and the family will just have to deal with it.  Fortunately for the family, I don't care about contests.


Quote from: cockpitbob on May 08, 2016, 12:18:29 ambut turning on individual breakers I've identified about 6 breakers that bring the noise floor up to beyond S-6.  It seems like I've got about 20 things to fix.

Bob, don't overlook the breaker itself.  I had a situation once where a flat garage roof leaked at a parapet and water ran inside the wall into a sub-panel.  The leak went unnoticed and over time corroded the terminals on several breakers.  I didn't catch it until the kitchen stove breaker tripped from overheating caused by arcing at the bad contact.  Replacing the breakers took care of a lot of my noise and re-roofing protected the new breakers.


Jim Boswell

Bob, what does your ground system look like? Apartments can be real difficult. Are you only running one band? If you are only running one band you might try a stub line on your ground. Back when I first got my novice, I could only use 15meters. The antennas needed for the 40,80 bands were just too big. Sounds like you started right, double checking power first. 73'S  KA5SIW


Hi Jim,
I have a shack desk in the basement with 2 ground rods just on the other side of the wall and everything solidly grounded to them.  The antenna is a 180' random wire and tuner.  I also operate out of an upstairs room with just an end fed half wave antenna.  Both locations have the same high noise levels on most bands:  40=S9, 20=S8, 15=S7.  When I throw the house's main breaker and run on a battery the noise goes down to whatever the atmosphere's noise floor is.


I have s9+ noise all the time. I throw the breaker and it goes to s9.

This past winter a limb ripped the line of the house and i fired up the radio and got s1-s2.

So it's not my neighbors since they have power but something between the line and the breaker.


All equipment turned off. Running radio on car battery. Still s7 to s9 noise. Constant.

Could be neighbor equipment. Guessing.

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If you can't find and cure the noise source(s), magnetic loop may help, should help, but are not easy to make eh! Another option is to buy a noise canceller. These can be very effective, some fiddling to get right, but work very well. There are two good makers of them, do a web search for it and read reviews. But I think costs some hundreds (200?) dollars.


Loops don't have to be expensive, I bought this one and love it, I have worked all across the US with it on 20 and 40 meters.