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Author Topic: Noise Levels  (Read 326 times)
WB2WIK
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Posts: 20542




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« on: July 09, 2004, 11:30:52 AM »

I agree the ladder line should not be coiled up.  If you don't want to cut it for some reason (although I can't think of any good ones), at least lay it out all over the place and don't coil it up.

Easiest method to determine if your noise is coming from other stuff inside your home is to operate your rig on a 12V battery temporarily (if it's capable of that) and pull the MAIN breaker to your house.  That will shut off everything except your rig, unless you use a UPS for your computer.  If so, bypass the UPS.

If that reduces the noise, turn OFF all the individual breakers, and turn the MAIN back ON.  Then, turn on one breaker at a time to see what impact it has on noise.  If the noise is coming from within your home, you'll find it soon enough this way.  If it's not, then at least you have that information to go on for additional noise hunts around the neighborhood.

Of course, it may just be real, honest wideband noise that's really there (generated mostly by the sun, but also from lightning activity and other tropospheric influences) -- but that shouldn't be S9 across all the bands.

WB2WIK/6
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N1ZHE
Member

Posts: 68




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« Reply #1 on: July 08, 2004, 11:56:08 PM »

I'm running a dipole cut for 80 meters. With a tuner I can work it all the way to 6 meters.

I'm using a 4:1 balun but I have an S9 noise level on all bands. This does not sound like power line noise, and BPL isn't being used or tested in my part of Maine.

The noise level is slowly getting worse as time goes by. I can only hear the strongest stations.

Any ideas how I can eliminate or minimize to noise?

David, N1ZHE
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X-WB1AUW
Member

Posts: 559




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« Reply #2 on: July 09, 2004, 12:18:45 AM »

Try unplugging your computer.

Disconnect your antenna, and see if the noise is still there.

Report back to us.

Bob
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N1ZHE
Member

Posts: 68




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« Reply #3 on: July 09, 2004, 12:22:35 AM »

I realize a bit more info is in order.

I have an Icom 706 MkIIG. There's a short coax jumper between the radio and my LDG AT-11MP Autotuner, then I have a 10 foot run of coax to the balun. Then 100 feet of 450 Ohm ladder line to the antenna.

Most of the ladder line is coiled up. The noise level was pretty bad before I coiled up the ladder line.

David, N1ZHE
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N1ZHE
Member

Posts: 68




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« Reply #4 on: July 09, 2004, 12:23:40 AM »

Thanks Bob. I'll try tomorrow as I must get up early for work.

David, N1ZHE
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N1ZHE
Member

Posts: 68




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« Reply #5 on: July 09, 2004, 05:08:58 AM »

A quick check (without disconnecting the computer) showed my S9 noise level dropped to S0 and no noise when I disconnected my antenna.

David, N1ZHE
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KZ1X
Member

Posts: 3227




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« Reply #6 on: July 09, 2004, 07:59:49 AM »

"Most of the ladder line is coiled up. The noise level was pretty bad before I coiled up the ladder line. "

Ladder line is only a transmission line while each conductor is spaced one line-width from each other.

Otherwise you have "something else" and in your case, coiled up, your ladder line appears more like either a short or an inductor, depending on frequency.

No wonder your noise level went down!
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KA5N
Member

Posts: 4380




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« Reply #7 on: July 09, 2004, 10:08:01 AM »

The ladder line should lead away from the antenna at a right angle and then to the balun.  Any surplus ladder line should be cut off and removed.  You cannot coil up ladder line.  
Also the bands have not been in good shape recently and there is a high noise level most of the time.
Good luck Allen
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KT8K
Member

Posts: 1490




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« Reply #8 on: July 09, 2004, 11:37:45 AM »

Still, S9 is a pretty high noise level, and if it is gradually getting worse I would suspect a combination of strong local RF, possibly on a completely different band, and something in the antenna system or nearby that is corroding.  Rust and other types of corrosion can rectify RF and generate tons of mixing products if you have a variety of strong signals present.  I have read accounts like yours where the cleaning or replacement of connectors, or even the removal of a rusting metal sun room or other nearby structure, could make a huge difference.  

If, on the other hand, you are in a very quiet, low-RF environment I would suggest running the radio off a battery temporarily and turning off the main breaker to the house.  If the noise goes away you can then start turning sections of the house back on, one room (or device) at a time.  People have reported high levels of electrical hash from electric blanket controllers, pool heaters, and all sorts of other electrical devices.  Something like that might be running in a neighbor's house or nearby business, too, and might be getting worse as some connector (a ground?) in their system corrodes.

Have you listened on an HT or AM/FM radio and found the noise there, too?  You can walk around with something like that and see if the noise gets stronger in any particular direction.  Sometimes street lamps can cause odd electrical noise as they burn out.  The ARRL has a good book on RFI that might help, and there have been other items on eHam that you can find through a search of the forums.
Good luck & good reception de kt8k - Tim
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K1CJS
Member

Posts: 5855




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« Reply #9 on: July 09, 2004, 09:02:40 PM »

Have you tried another antenna?  Just a 20 foot piece of wire will do.  (For receiving only!)  See if you've still got the noise on your rig.  If you do, there is a possibility a splice is going bad on a power line somewhere in your neighborhood.  If you can take your rig mobile, see if there is a hot spot anywhere around your house.

I'd try this after ruling out most other probabilities, though.
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