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Author Topic: Excessive Noise  (Read 563 times)
KD0INK
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Posts: 5




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« on: December 03, 2009, 07:04:01 PM »

I am a new ham and would very much appreciate advice on excessive receiver noise.
I have a Yaesu FT-950 with a Hustler 5BTV ground mounted vertical antenna with plenty of radials.  The rig works fantastic during the daytime, but at night it is nearly unusable due to excessive S9+ noise in the receiver. It is so bad that I can rarely hear transmissions on 80 meters.  All bands are noisy with the exception of 10 and 160 meters.  The noise is constant static with no fluctuations, however it does begin fading a bit very late at night and into the early morning.  
I have eliminated the obvious possible offenders within the house and can only guess that electrical noise in the subdivision might be the source.
Any ideas, thoughts, or suggestions would be appreciated.
Thanks
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W5DXP
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« Reply #1 on: December 04, 2009, 06:04:12 AM »

At my previous QTH, my noise problem subsided when I went from a vertical antenna to a horizontal antenna. The vertical's noise was about 2 S-units higher than the horizontal's noise on 40m.
--
73, Cecil, w5dxp.com
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
DIPOLE
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Posts: 176




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« Reply #2 on: December 04, 2009, 07:01:07 AM »

The thing about verticals is that they "hear" equally well from all directions.  This means they are great for scanning the bands, but not so great at directional hearing. This is particularly an issue if there is an industrial noise source near your QTH.  But overall, high noise is sometimes a fact of life on the HF bands. HF noise varies with season, atmospheric conditions, sun spots, etc. You should try adding some attenuation if your rig allows such. I almost always attenuate until the general noise just does drop off the scope. This still allows me to hear signals above the noise level while at the same time lowering the listening fatigue factor.
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DIPOLE
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Posts: 176




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« Reply #3 on: December 04, 2009, 07:06:52 AM »

If you don't have a scope, just know that -6 or even -12db of attenuation is commonly required to reduce the noise to a tolerable level.  If you don't have an attenuation control, try reducing your RF gain.  Having the RF gain at maximum is not always the best setting, that's why there is a knob for it Smiley

- Barry
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WB5JEO
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« Reply #4 on: December 04, 2009, 11:03:04 AM »

A dramatic onset of noise at dark in an urban setting strongly suggests automatic lighting. It might be a street light or lights. And if it's a subdivision where one builder built a lot of the houses, they might well have used the same noisy photocell operated yard or porch lights on all of them. I mention that because it sounds like it starts fading at dawn, rather than just cutting off. And there also may be things like dusk to dawn lighting on a subdivision sign or elsewhere.

I think I'd first sit down before dusk and listen to it come on and see if it's all there, all at once full strength. Or if it comes in in stages, a little louder each stage as more lights come on. I'm hoping this is a new problem, that you operated there before without hearing it. That would mean it's likely one source that's starting to go bad, or maybe one noisy device that replaced another quiet one.

If you just started or just moved in, in other words, you've never operated there without the night noise, it could be bad, especially if it comes in gradually and fades out in steps. It could be a giant problem to find all the sources and a bigger problem to try to get them replaced.

Do the listening at dusk and see what you might expect. Either way, I'd set out at night with a portable AM radio or, even better, with a portable SW receiver. You can also rig your 950 to power up in the car (you won't be transmitting) and drive it around with a short piece of wire stuck into the coax connector. See if you can localize a noise source at the nearest street lamp. Then move to the next and the next. If it's really loud on the portable before you leave the house, reduce the antenna size until you localize it. If I found that a half dozen lights in each direction were noisy, meaning the noise peaked when I stood under each one, I'd figure they were all noisy. God knows how the city or whoever takes care of them is going to take that request. At least you've kind of got the FCC behind you there. Most of their enforcement filings for RFI are against power providers. But the first job is to see if that's the problem.

Obviously, if it turns out to be just one light, they should fix it. And if it turns out to be one neighbor's yard light, you might ought to offer to buy them a replacement, since you're the one who cares. The only thing that makes it sound like it might be neighbors' lights is that it sounds like it begins fading late at night and is gone by morning. That might be people turning off automatic lights when they go to bed.

Or it might be something else entirely, but you'll learn a lot walking around with the portable. I guess it's even possible that it's a transformer going bad and making noise when it comes under the heavy load in the evening. That's one of the easier ones to get fixed, since it's evidence of a fault and suggests the transformer's going to fail one day.
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DIPOLE
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« Reply #5 on: December 04, 2009, 05:33:00 PM »

Yeah, speaking of lights... I once had a noise problem that turned out to be the transformers on the low voltage lights in the kitchen area.  The XYL liked having her lights on, even though it made for rough listening on HF. I finally replaced them with 120v lighting to eliminate the transformers - noise eliminated.
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WE1X
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Posts: 326




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« Reply #6 on: December 04, 2009, 07:58:55 PM »

My neighbor has either a mercury or sodium vapor flood light. A couple of  years ago out of no where I got S7 to S9+ noise on all bands, complete bands. Came on at dusk and disappeared early morning. I finally tracked it down to his light. Apparently when the bulb is on its last legs the noise level goes through the roof. Was that way for about 3 months until it died. Nope, he wasn't in any hurry to change it.

Harry WE1X
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AI7RR
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Posts: 164




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« Reply #7 on: December 07, 2009, 04:03:03 PM »

The 80m band of late has been terrible (long) and you may be experiencing some of that. Lots of static and very low signal levels.

Do you have a plasma tv? Does one of your neighbors have a plasma tv?

Vertical antennas are very susceptible to power line noise. This time of year with lots of moisture in the air will often times cause that noise to increase.

A little more information regarding your situation may help the forum to evaluate your issues. Questions to answer include: New installation, radio or antenna? New to ham radio? New QTH? When did you notice the problem? Have you confirmed it's every day or every night or is it perhaps random? Is it isolated to only a portion of a band or across several bands? As mention before, can it be associated with public works activity (street lights, etc)?

73,,Roger
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AI7RR
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Posts: 164




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« Reply #8 on: December 07, 2009, 04:17:25 PM »

After re-reading your post, I see that you did offer quite a bit of the information I suggested. My apologies. That's my old age rearing it's ugly head, again.

73..Roger
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KJ4KET
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Posts: 73




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« Reply #9 on: December 08, 2009, 04:32:12 AM »

I sometimes get overwhelming electrical noise, over s9.  Fortunately, the noise is usually local in origin.  I have an MFJ noise limiting box (which I blew up once, but managed to fix).  It has a sensing antenna that feeds the noise out of phase with the main antenna signal.  It is able literally to zero out the local S9 noise completely.

However, often you hear a similar noise and think it's local, but it is not, and then this device doesn't really work.  However, I am glad I have it - in some situations it can truly be an amazing gadget.

There are also circuit diagrams on the net for those who would prefer to build a similar phasing device.

Regards

David
KJ4KET
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W8JI
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« Reply #10 on: December 08, 2009, 04:56:57 AM »

There are also circuit diagrams on the net for those who would prefer to build a similar phasing device.

Regards

David
KJ4KET

Some of the circuit diagrams on the net won't work at all. They don't rotate phase very much, if at all. The "QRN Squasher" is one example.

Tom
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