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Author Topic: Power Line Noise problem: K9AY Loop vs 500 ft Beverage- is one less susceptible?  (Read 3459 times)
W3HKK
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« on: February 08, 2013, 08:06:31 AM »

Im dealing with 59+20 power line noise.  Long term.  Im working with the utility, but would like to know  if anyone has  compared the above two antennas and can tell me what difference they have noticed in power line noise rejection between them??? By how many dB/ S units?

Thanks
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W0BTU
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« Reply #1 on: February 08, 2013, 02:39:57 PM »

Depends on the band; but generally, a Beverage has a better pattern and therefore should be superior.
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K2DC
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« Reply #2 on: February 09, 2013, 03:36:38 AM »

I agree with BTU, except if the noise source is very close.  If it's in the near field of the beverage, the pattern hasn't formed yet and you never know.

73,

Don, K2DC
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W3HKK
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« Reply #3 on: February 09, 2013, 04:07:38 AM »

K9AY claims a  20-30 db F/B, and its steerable.  So putting the null on the source of the PLN ought to do something.   I have the direction identified.

Also, with a  K9AY they recommend 15 db preamplification to make output equal to a Beverage.  My receiver has two stages of preamplification ( an   IC-7600) so  couldnt I do without the external preamp?
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N6AJR
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« Reply #4 on: February 09, 2013, 04:50:36 PM »

Pixel Techonoligies has a loop fo about 400 bucks complete, just add coax and a mount. it too is steerable so you put the noise in the null are of the rx loop.
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KC4MOP
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« Reply #5 on: February 09, 2013, 05:29:17 PM »

Pixel Techonoligies has a loop fo about 400 bucks complete, just add coax and a mount. it too is steerable so you put the noise in the null are of the rx loop.

I love my Pixel loop too. The loop will do a nice job. But that large signal you have in your radio is really close. I / We assume you checked everything in your house?? Switching power supplies, LED lighting, Plasma TV's. Cable TV modems.
Noise that close will blank out even a super receiver. To "help the utility" you can drive around with even a car radio tuned to the end of the expanded band and it will help locate your noise. We do not know how much investigation you have done, so far. Can you tell us more about your noise?
Fred
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W3HKK
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« Reply #6 on: February 09, 2013, 07:33:55 PM »

I  used my 6M yagi  and  xcvr on AM mode to  graph a major lobe  at about 255 degrees.  Last summer a friend and i drove around the two streets  I suspected and found a power pole with major noise using his  AM radio with a loop to walk right up to the offending pole.  My car radio on AM identified the next pole to the north.  So we  have a good idea  that the problem is hardware on one of those two poles.  But after notifying the local utility, nothing was done.

Ive again notified them and will follow up again next week before  notifying the FCC. 

I also have a phased 40 meter array ( a pair of ground planes beaming ENE and WSW) that show more noise when  beaming WSW.

So we now have a good idea about where it is.

The RFI peaks on 160m at 20/9, is  loud on 80m at S 7 and  is annoying on 40m at S5-7, then diminishes as you go up in frequency.

All my antennas are  inverted L's or  ground planes, which are  more suceptible to  PLN that a dipole or yagi would be.

Clearly something is  arcing as there are spikes across my bandscope, likely due to a bad insulator, broken  ground wire or loose hardware at or near the poles in question.

Up until two years ago I had a beautiful quiet QTH and working 160m and 80m was fun.
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W0BTU
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« Reply #7 on: February 09, 2013, 07:47:35 PM »

Actually, maybe you ought to have both the K9AY and the Beverage(s). As has often been said, you can't have too many receive antennas. At different times, and under different conditions, each antenna will take turns being the best one.
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W0BTU
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« Reply #8 on: February 09, 2013, 07:51:17 PM »

My car radio on AM identified the next pole to the north.  So we  have a good idea  that the problem is hardware on one of those two poles. 

I used to give offending power poles a good rap with a ten pound hand sledge. Sometimes, that would make the noise change or even go away for awhile.
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KC4MOP
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« Reply #9 on: February 10, 2013, 04:40:26 AM »

My car radio on AM identified the next pole to the north.  So we  have a good idea  that the problem is hardware on one of those two poles. 

I used to give offending power poles a good rap with a ten pound hand sledge. Sometimes, that would make the noise change or even go away for awhile.

Be careful using a sledge hammer....It may cause the hardware up there to fall on you. A lot of the USA grid is over 50 yrs old and ready to crumble at any time.
And W3HKK start a letter campaign to the FCC if the utility is dragging their heals. Unfortunately other countries do not have any systems in place to protect Ham ops from defective electrical grids.
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AA4HA
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« Reply #10 on: February 10, 2013, 06:52:45 AM »

Make sure your beverage is terminated with a good non-inductive resistor of sufficient power handling rating so it is not va-poo-rized every time a cloud burps out a flash of lighting. Getting a good ground at the end of that beverage is pretty important.

If you do not, then it is nothing more than just a low, random length chunk of wire attached to a 9:1 balun.

Beverages are not renowned as particularly quiet antennas. (I have several and I am quite pleased for the application they are in). There are some others like delta, flag or pennant antennas. Tom (W8JI) or Dallas Lankford have done quite a bit of work on the larger receive antennas and would be invaluable references (Google them).
« Last Edit: February 10, 2013, 06:59:06 AM by AA4HA » Logged

Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
K4SAV
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« Reply #11 on: February 10, 2013, 07:49:58 AM »

The Beverage will have a superior pattern and should have less noise unless the Beverage is pointed right at the source, in which case they will be about the same.  Neither antenna will help much if the noise is very close to you, however if you have already identified a direction that means it is probably not in your house.  The null of a K9AY may or may not be of help.  That null is generally not at zero degrees elevation angle.  It's usually at 25-30 degrees elevation and very narrow in the azimuth direction.  If it's a power pole some distance from your house it will be coming in at close to zero degrees elevation, and it's unlikely that you will get it to hit the null.

Noise of S9+20 dB should be very close to you and a bad noise source to boot.  It would be worthwhile trying to track it.  Maybe get some help from local hams that have some equipment.  With a noise source that big, you aren't going to be happy with trying to solve the problem with a better receiving antenna or a noise canceller.

Power line noise can travel a long distance however.  The worse case I have experienced was S9 noise on my 160M receiving array from a distance of 3 miles.  It has to be a big noise source to do that.  There is currently another source (S7-S8) in the same area.  I correlated it with what was being received at home.  I haven't located it exactly yet, because it is intermittent and tends to hide when I get close to it, and on top of that there are multiple small sources in the same area which aren't being heard at home.  Power company people will have no success at locating noise sources at those distances.

Small sources very close to you can create big S meter readings and those can be hard to find.  If it is at a large distance it has to be a big source and it will sound very big when you get near it.  I use the car AM radio to get in the area, then the MFJ-856 to isolate it to the pole, then a homemade ultrasonic detector to isolate it to the component on the pole.  The biggest problem I have when looking for noise sources is identifying which noise source is the one I am hearing on my radio.  I usually find many sources when I get close to them, but most of them I don't hear at home.  If they have any particular pattern that can be correlated with the noise at home, the job becomes much easier.  I can't inundate the power company with repair requests for everything I find.  They will start ignoring me if I do that.

Unless you get a person at the power company that has expertise in tracking these kind of problems, you may not have much success.  The average repairman will be looking for burn marks or smoke.  That is rare.

Jerry, K4SAV
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KB4QAA
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« Reply #12 on: February 10, 2013, 05:53:37 PM »

Don't forget to send a complaint letter to your State Utility Commission and/or State Corporation Commission.
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W1VT
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« Reply #13 on: February 11, 2013, 04:01:02 AM »

You can design or build and adjust a short beverage for a cleaner pattern than a long one.  There are preferred lengths for getting a good pattern--so I tweaked my half wavelength beverage for a good front/back--it dropped 6Y5WJ from loud to in the noise on 80M.   Grin
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W3HKK
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« Reply #14 on: February 11, 2013, 06:57:03 AM »

W1VT: Thats encouraging!  I can more easily do a half wave on 160 than a full wave.   Is your half wave beverage cut for 160 or 80m?    how did you tweak your half wave Beverage?  Shortening or lengthening it and uprooting the ground rod at one end each time you changed lengths? Or is there a simpler  more effective way? ie changing termination resistance?

Thanks.
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