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Author Topic: 80 meter noise level  (Read 2714 times)
NT6U
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Posts: 68




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« on: December 18, 2011, 07:42:36 AM »

  I have a s-10+ noise level on 80/75 meters constant day and night.  I have not been on 80 for a long time 2007 or so and don't recall the noise floor this high, however 2 months ago I installed inverted V, peak above roof 15 feet, above ground level 40 feet. Good signal rpts. if I could hear "them".  I had the noise thought it may be from something in my house, so I installed a DX engineering Thunderbolt 8040, a 55 foot vertical way in the back yard, The noise is worse.  I know verticals are noisier than dipoles yet I was hoping being 60 to 70 feet from the house might help.   There are 2  ground rods and 50 radials, not all perfect but long radials for the vertical.   40 meter dipole at 45 feet is fine for noise.  H.F. yagi 10-15-20 meter excellent reception noise floor as well.  I live in Corona Calif. near the 15 fwy and the 60 if location matters.  Any help would be appreciated.  By the way my wife hates the vertical in the backyard, beware future buyers. Shocked
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W4VR
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« Reply #1 on: December 18, 2011, 08:26:11 AM »

if it sounds like eggs frying when you listen to it in the AM mode it's probably power line interference.
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NT6U
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Posts: 68




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« Reply #2 on: December 18, 2011, 08:36:07 AM »

It sounds more like a barbers shears. LOUD Sad
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K8AXW
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« Reply #3 on: December 18, 2011, 08:36:20 AM »

Having a noise level this high on just one band is very strange and while there might be a difference in noise levels between a vertical and any other kind of antenna, the difference shouldn't be enough to warrant installing a different antenna style in order to use a band.  

Solving problems like yours usually start with shutting down everything in your house except the circuit feeding your rig and seeing if the noise goes away.  Before getting anyone else involved it's always best to eliminate your own house as the problem.

If you have a different rig that you can put on the 80m band, try that and see if there's a difference.  If you don't, perhaps you can get a fellow ham to bring his rig over and see if there's a difference.  This will eliminate the possibility that there is something wrong with the rig.

After that I'd try to get help from other hams in the area and see if any have equipment that can help you find the source of noise.  

Several years ago a ham two streets down and I both had a problem with noise but it went from 3.5MHz to 30MHz.  We identified it as power line noise and reported it.  While it took quite a while the power company finally identified the problem and corrected it.

The last time I had an interference problem it was very local and the power company came and shut of power to all the houses fed from our common pole pig.  Long story short, it was a doorbell transformer in a neighbor's house.  However, once again, the interference was all over the HF spectrum.  Not just one band.
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WB6BYU
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Posts: 13010




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« Reply #4 on: December 18, 2011, 09:28:07 AM »

The noise might be picked up from the antenna, or, if you have common mode
currents on the feedline, along the feedline itself acting as part of the antenna.
Since the feedline runs closer to the electronic noise makers inside the house
than the antenna, this actually is a fairly common problem, and one that can
often be solved by installing an effective balun.  It is possible to have it on
some bands and not others because the amount of common mode current
depends on the feedline length in wavelengths, along with many other
factors.

One thing you might try is to disconnect the feedline at the base of the
vertical and see if the noise level drops as much as you would expect.  If
not, you may be picking up noise on the coax.

Certainly a good first step is to run the rig from a battery and shut off the
house power at the main breaker.  If that makes a difference, then you can
kill the circuits one at a time to narrow it down.  There are lots of noise
sources in the modern house - battery chargers, computers, TV sets (even
when off, if they can be turned on by remote control), heater controllers,
computer networks and routers, switched mode power supplies, CFL lamps,
etc.  If you can narrow it down to part of your house, then a hand-held
receiver, or a small pickup loop on the end of a coax to your rig, might help
to sniff out where the noise is strongest.

If it is external to the house, then take the rig mobile with a loop antenna
(or whatever you can manage) and see if you can find where the noise is
strongest.


But you are also fortunate to live in one of the few parts of the country where
there are a number of hams around who have hand-held 80m DF receivers.
They aren't perfect, especially when the noise is being propagated down
a power line rather than coming from a point source.  But if you get stumped
otherwise, contact Joe Moell K0OV through his web site at

http://www.homingin.com/

and he may be able to find someone nearby who can help you.
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NT6U
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Posts: 68




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« Reply #5 on: December 18, 2011, 10:05:02 AM »

Thanks so far.  I have multiple H.F. rigs.  I tried different rigs noise still there. Power is on independent sub panel to shack. I shut everything(the house) down noise is still there.  I will run one of the smaller rigs off a 12 volt battery source next,shutting all house circuits down, and see. 
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NT6U
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Posts: 68




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« Reply #6 on: December 18, 2011, 10:11:31 AM »

Further the vertical is fed through a current choke. Still noise with or without the choke.  I have the 80 mtr. dipole still attached to a six position antenna switch so I can switch all antennas very quickly, it is fed thru a 1 to 1 balun.  Both 80's  have noise just the vertical is noisier, of course.  What is a normal noise floor for 80 for most of you?  Maybe I expect to much??
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WB6BYU
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Posts: 13010




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« Reply #7 on: December 18, 2011, 11:15:16 AM »

S1 or S2.  Maybe higher when the band is open and there is a lot of thunderstorm
noise.  But I'm out in the country with the nearest neighbors 1/4 mile away.
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ZS5WC
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« Reply #8 on: December 18, 2011, 11:40:40 AM »

Sounds like a local noise, unless you have close neighbours.

Things to check: Plasma TV's , Switch mode supplies, Energy saver lamps, ADSL routers, Sattelite TV decoders, and the BIG culprit--cellphone chargers.
For some reason people never unplug them even if their phones are not on charge!.
Solar power inverters (not sine wave) also.

I have a handheld scanner that I use to find the noise--maybe you have a portable that you can use to find the noise?.

73 de William
ZS4L / ZS5WC
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K0ZN
Member

Posts: 1531




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« Reply #9 on: December 20, 2011, 06:05:13 PM »

Unfortunately, I have picked up a lot of experience chasing down power line noise.  A couple of hints:  1.) as you noted, CLEAR your own house first to make sure
the noise is not generated in your house. (The Power company RFI guys tend to be a little curt when they find YOU are the problem !)  2.) Drive around the area
using just the AM radio in the car to see if you can hear anything similar. 3.)  Put the HF rig in the car and use a short whip.... 6 m is probably too much....you want a "bad" antenna to reduce sensitivity; a 2 M  1/4 wave whip is often fine....drive around listening on the freq. where the noise is loudest and see if you can get a good guess where it is strongest.  4.) Use a VHF AM (I use a aircraft VHF band receiver tuned to 132 Mhz) and drive around using the 2 M whip. Often the VHF AM rig will get you very close to
the noise if it is power line noise.  If you want to make a 4 element Yagi for the VHF AM frequency, that helps too. Usually, with a combination of these you can get down to a pole or two.

If the noise is on a very narrow band of frequencies, odd favor it may be some type of consumer or homeowner electronic or consumer device generating it.

I know our power company "noise guy" pretty well....fortunately, he is a Ham ( VERY handy!).  He (the company) has commercial equipment for finding noise, one of which is
a 300 Mhz AM receiver and a 5 element yagi antenna. This set uip is VERY effective. I guess you could buy or build one.... converting a 220 Mhz rig to AM and get a yagi would also work well. The power co.
also has a ultra sonic detector.....it can hear buzzes and arc's you can't but if you get close to a noise it is not horribly uncommon to flat out HEAR the arc or buzzing.

There is a wild mirad of things related to power lines that get noisy.....  damaged lightning arrestors, excess slack in wires, corroded hardware, cracked insulators, dirty insulators, loose wires, loose or corroded ground wires!, current induced into phone or CATV lines below the power lines creating noise or arc's. Check ALL grounds of any and all types on the power lines, near by CATV, phone, etc. I have heard of loose U nails on ground wires running down wooden poles causing RFI.... trees touching power
lines can be an issue.

Chasing RFI from power lines is like any job:  if you have the right tools it is usually much easier to fix the problem. THere are some books on this subject: pick one up.

Frankly, you are probably better off with a line noise problem than a noise being generated by some device a neighbor owns, as the power company *should* feel and be more obligated to correct the problem. You never know how a neighbor will react or cooperate. In some cases, you may need to offer to pay to fix their problem!
That is not fun, but it is better than losing you hobby.  "Just the cost of doing business."

Good luck, you have my sympathy.

73,  K0ZN
« Last Edit: December 20, 2011, 06:14:10 PM by K0ZN » Logged
K4KMG
Member

Posts: 16




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« Reply #10 on: December 22, 2011, 10:47:36 AM »


I have a handheld scanner that I use to find the noise--maybe you have a portable that you can use to find the noise?.

73 de William
ZS4L / ZS5WC

Hi William. Would you mind explaining this further? (with the scanner) How it's done?

Thanks
73, Tom
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