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Harpoonman
| | Posted on Tuesday, August 21, 2001 - 3:31 pm: | 
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Here are a couple of different tech questions for you all. I am hoping that someone here might be familiar with two kinds of interference that I have been getting over my Cobra 2000 station.
I am running the Cobra to an IMAX 2000 antenna mounted about 25 feet above the ground (at the antenna's base). The antenna base is 6-7 feet above the roof line of my house (asphalt shingle). I am using about 108 feet of the thicker coax (I can never seem to remember the coax number!) and the SWR is good all across the band. I transmit rather well with this set up and the station's receive is usually excellent.
Now, let me describe for you the two types of interference that I've been getting, below. I'd like to figure some way to either filter this stuff out or find its source, if possible, to correct the problem. Here goes.
Interference # 1 (The Cat):
This interference produces a nasty "squalling" sound when the radio is on SSB. The noise generally starts off low and sort of "creeps" onto the channel, gradually increasing in volume and intensity over a period of 30-60 seconds until virtually all but the closest stations cannot be easily heard. This interference will persist from a minute or so to several minutes, but it is most definitely not a continuous, on-going thing. At its peak, the noise sounds like some old cat that's having its tail stepped on! Horrible! After a while, the noise will gradually creep on out. It will invariably return later, but there seems to be no regular time of occurrance or interval between occurrances.
I have also noticed that The Cat is not broad-banded and when I scan the channels I can almost always hear it on one or two or three different channels in the regular 40 channel CB spectrum. This noise seems to slowly "slide" up (and maybe down) the band over time. Also, The Cat sounds different when picking it up on AM. On AM, the noise sounds more like static or some type of electrical interference. When The Cat is present and howling on, say, channel 36 LSB, you can hear it on that channel in the AM mode, but you won't hear it on channel 36 USB, or on any of the nearby channels at all. As it dissipates on that channel, it usually moves up to 36 USB, then eventually on to channel 37 LSB. Sometimes, it seems to go from the upper channels and side bands to the lower channels and side bands (in other words it doesn't seem to always move across the band in the same direction). Sometimes, it will skip a bunch of channels.
My theory on The Cat is that it is a natural, atmosperically-generated RF noise perhaps caused by particles striking layers of the upper atmosphere. If this is the case, then I realize that there may be little I can do to get rid of it. Otherwise, I suppose it could be man-made and someone is deliberately generating this noise, somehow, just to irritate CBers (although this seems unlikely and little silly). Others here in the Baltimore area have heard it, too, but no one seems to have an authoritative explanation on it. And it seems to drive me more batty than others. It is so loud and obnoxious that I often have to turn the volume nearly all the way off! Any ideas out there??
Interference # 2 (Buzz-Buzz):
This sounds like the electrical interference generated by an arc somewhere. It tends to start more abruptly than The Cat, but it, too, usually lasts only a short time and recurrs frequently and rather randomly. It also ends very abruptly, like a switch being thrown. This interference is broad-banded. I can pick it up from channel 1 to 40 at the same time and it sounds pretty much the same whether I'm on SSB or AM. It, too, is very loud and makes hearing more than the nearest stations quite difficult!
My take on Buzz-Buzz is that it is caused by an electrical arc, perhaps in a step-down transformer somewhere in my neighborhood. But, I haven't been able to pinpoint the source. It does not appear to be coming from somewhere in my house (such as the air-conditioning compressor or blower fan). What do you all think?
Is there any way to filter these interferences out? Would better grounding the antenna system or the radio itself help? Any suggestions? I feel confident that someone here on Copper Talk knows what these bothersome noises are!
Thanks for your patience and your help, too!
Adam |
Harpoonman
| | Posted on Friday, August 31, 2001 - 8:06 pm: |
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OK, I realize that I am long-winded much of the time, but no one here on the Forum is even the least bit interested in the interferences I have described above?? No one here has any ideas of what could be causing such interference, especially The Cat, or has any suggestions on how to correct it?
Aw..come on!
Adam |
Anonymous
| | Posted on Saturday, September 01, 2001 - 4:06 am: |
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Adam what kind of power supply are you running? Do you have anything like a computer close by your radio? My base setup pickes up all kinds of junk QRM from my computer and any running electrical motor be it a drill or circular saw. Try putting some chokes on your coax, power supply power cord, each wire of your radio's power cord, and if your really feeling zesty put one on your mic as well. Hopefully this will filter out or absorb your weird noises.
Paul |
bruce
| | Posted on Saturday, September 01, 2001 - 11:16 am: |
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if you hear it only on ssb it might be a reciver problem but since you are hearing it on am too it could be a local computer. my 800 meg cel machine puts out a wide range of noise which i can hear on my driveway just a thought |
vernonott
| | Posted on Saturday, September 01, 2001 - 12:11 pm: |
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Harpoonman:You need to see if you get the same irritating noise on your mobile outside of your house and around your neighborhood.A couple of years ago I had a bad buzzing on my base .I climbed into my mobile and didn't have it there.I drove around the neighbor hood and about a mile away my mobile picked it up loud and clear from a power pole with four transformers on it.The power company was contacted and they found one of the transformers was failing.After it was changed out the buzz went away from my base.Probably the reason my mobile didn't pick it up was the difference between my base and mobile antennas.73's |
Bigbob
| | Posted on Tuesday, January 01, 2002 - 10:19 am: |
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Harpoonman,had a sound like both you describe the cat came from the tv surround sound monitor when it was on,the other was from an arc-welder one block away. |
Taz
| | Posted on Thursday, January 03, 2002 - 10:32 am: |
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i know some vcr's tv's and am/fm radios, coax problems like a tear in the side. definetly moniters do this. |
Biged
| | Posted on Friday, January 11, 2002 - 10:20 pm: |
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harpoonman,Sounds like what you need is an oxorcism.Just kidding.I worked for the cable co. for a few years and have experienced plenty of service calls that dealt with "Ingress".This is when a tv,vcr,computer speakers,stereo, or even a cb is overcome by another signal of or about the same frequencie.In other words,Some paging companies have a freq. that is standard but the same as a tv channel and if your coax has a pinhole in it or a bad connector os just plain worn out, the outer jacket maybe cracked, this would be a cause of ingress."egress" is just the opposite.That is when you are the unwanted noise generator.Here is a quick example that you can probably relate to if you run an antron 99.If your neighbors tv is being blown away every time you key up your mic,you are delivering egress out of your antenna and your neighbor is recieving ingress into his tv.To sum it all up,you may be dealing with something of this nature.Try turning off everything in your house one at a time when this happenes.If you know anybodt that works for a cable co. Maybe you can get them to let you use there RF meter.If you hook up a set of rabbit ears to this peice of equipment and dial in the frequencie that this problem exists on and walk around your house with it and use it as a field srength meter.It may just eventually lead you towards the source.If all else fails , try a diffrent radio.Hope this is some help.Good luck!! |
2ec837
| | Posted on Saturday, January 19, 2002 - 9:29 pm: |
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Has anyone been bothered by the "Russian Woodpecker" QRM? I live in the northeast and have this noise every morning.It is usally about S/9 and covering from 27.495 to 27.605. |
Ohiobiker
| | Posted on Saturday, January 19, 2002 - 11:09 pm: |
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THE RUSSIAN "WOODPECKER"?... OMG...NOW I HAVE HEARD IT ALL! YES WE HAVE IT HERE IN OHIO...I THINK ITS ON THE INDANGERED SPECIES LIST...IT COMES SEVERAL TIMES A DAY HERE AT MY QTH. I LIVE IN CENTRAL SOUTHERN OHIO, CARROLL COUNTY. IF I EVER SEE IT I WILL POISION THE LITTLE BASTARDS FOOD SOURCE! HAVE A GOOD ONE AND THANKS...MY FRIENDS AND I HAD NO NAME FOR THIS NOISE...WE DO NOW...THANKS AGAIN...WALT...aka...OHIOBIKER"575" |
2ec837
| | Posted on Monday, January 21, 2002 - 2:20 am: |
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I first heard the term "Russian Woodpecker" back in the late 70's. It was believed to be OTHR (over the horizon radar) coming from the ex-USSR. It was a common term in ham and shortwave magazines.I think it is kind of odd that it resurfaced after all this time,unless it has somthing to do with the aftermath of 9/11.If you do see it,PLEASE use a double dose of poison!!
73 Carmen 2EC837,TA4313,PE262 etc... |
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