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Author Topic: Too much noise!  (Read 1184 times)
N3WWN
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Posts: 9


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« on: May 31, 2001, 04:04:18 PM »

Hi!

I've been attempting to use 6m with grey line propagation and have a lot of trouble with, what I think is, local noise.  

My last contact was in Florida (I'm in Pennsylvania).  I received an RS report of 52 and a compliment on my terrific audio, much to my suprise!

I sent an RS reports of 37 (if i recall correctly).  The noise floor was around S5 to S7 most of the time.  Normally, if the noise is low, an S7 signal is great, but when the noise floor is up, it's barely enough to copy a signal.

For instance, last night, the noise floor stayed between S9 and S9+10 for the entire duration of probably grey line propagation.   So much for working a few fellow hams last night.

To sum up, my question is this:  What can I/should I do about the noise at my QTH?  

Should I use a noise cancelling antenna such as a MFJ-1026 or similar (need one that covers 6m)?

Is a phaser the same as a noise cancelling antenna?

Thanks for taking the time to read this and I appreciate any replies!

73,

-Rich
 N3WWN
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WA2AEH
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Posts: 21




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« Reply #1 on: May 31, 2001, 04:55:29 PM »

Maybe I'm not fully informed but, I never heard of anyone working grey line on 6 meters.  I would like someone to verify this for me if possible.  I thought grey line was useful from 160 meters to 20 meters.

As to the noise, at 6 meter frequencies, it should not be a factor.  I would check your antenna for loose elements or loose coax connectors.  I would imagine noise at 50 mhz would have to be very close to your antenna.

K2WH
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K6LO
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Posts: 226




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« Reply #2 on: May 31, 2001, 05:53:46 PM »

Sounds like you have some local electrical noise.  If it is on the primary, the your local utility is responsible for eliminating it.  If it proves elusive, try an ANC-4 or perhaps even the MFJ.  I have occassional secondary noise on 160 at my QTH, and my ANC-4 completely eliminates it.

Quick tip: If your 6 meter radio has AM receive capability, then check AM under the noise condition. If you hear a pronounced hum demodulated, then it is electrical, rather than some odd broad RF source.

Good luck - I know it is annoying.

73 - Luke
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RobertKoernerExAE7G
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Posts: 1435




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« Reply #3 on: May 31, 2001, 05:57:43 PM »

Since your rig has 10, 12 and 15 meters in it, see if the noise is present on ten meters.  If it is, see if someone in the club you belong to has 10 meter mobile rig so that you can drive around your area trying to find the source of the noise; you could use a CB rig also -- one with the old VU meters.  When you get near the source, short the antenna to reduce the signal.

If you have a rotating TV antenna, you should be getting visable interference on channel 2-6.  You can DF with the TV antenna.

Also, unplug your computer and monitor to see if you are generating the interference.  Disconnect any RF devices connected to your computer.

If the interference is in your house, open the breakers in your breaker box, one at a time.

Good luck

Bob
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WB2WIK
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Posts: 20611




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« Reply #4 on: May 31, 2001, 07:01:09 PM »

I think gray line is not really the correct term here.  Gray line effect is for ionospheric propagation, which Pennsylvania to Florida is obviously not!  PA to FL would normally be Sporadic-E, although could be achieved using meteor scatter, tropospheric forward scatter and other methods -- none of which have anything to do with the gray line.

However, the noise problem is another subject.  Great suggestions here, so far!  You might take them one step further by operating your rig from a car battery temporarily, while you pull the MAIN breaker from the service panel of your house, and see what effect that has on the noise.  If it has "no" effect, then the noise is probably not generated in your own home, but elsewhere.  

But you might be surprised to find the noise level drop several "S" units!  If so, the noise is locally generated (something or various things in your home), and you can try to isolate it by turning on and off circuit breakers, etc.  This process can take several hours, but WOW is it worth it when you finally find out what's making all the noise!

73 de Steve WB2WIK/6
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KL7IPV
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Posts: 984




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« Reply #5 on: June 01, 2001, 01:21:48 AM »

One thing not mentioned but was a topic here this week is lamps and light slide switches. If you have a touch lamp or a dimmer switch on your lights, see if you can deactivate them first. They are real noise generators. Also, you didn't say; but are you using a switching power supply?  They also generate noise.  If you can answer "No" to all those you are back to the suggestions of pulling breaker switches to isolate the trouble. Good luck.
Frank
KL7IPV
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N3WWN
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Posts: 9


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« Reply #6 on: June 01, 2001, 11:27:00 AM »

Perhaps it's not grey line *shrug*

I figured it was since the band was opening right along the grey line just after sunset for me.  

Most of the docs I have read about grey line simply state that is is very efficient for long distance communications.

If anyone has more grey line info, I'd appreciate learning more about it.

As far as the noise is concerned, my QTH is located in a very noisy area, unfortunately.  When the noise is low, there is no problem pulling out weak signals, but when the noise is high here, it effects 2m, 6m, and family radio service.  All of these on different radios, and all but 6m are battery powered.

Thanks for the reply and 73!

-Rich
 N3WWN
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N3WWN
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Posts: 9


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« Reply #7 on: June 01, 2001, 11:30:27 AM »

Oh, and I forgot to mention:

Thanks for all the great tips on possible noise sources...I'll try to locate them as soon as I can.  

I'm not sure how much it will help, but any improvement is, after all, an improvement.  I've talked to a few other local hams who have the same problem with this area's noise floor.

Thanks again!

-Rich
 N3WWN
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AC5UP
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Posts: 3893




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« Reply #8 on: June 01, 2001, 11:59:18 AM »

As a general FYI...

Six Meters is a fairly quiet band at my QTH as long as I stay below 51 MHz. We have a local Channel 2 that gets _real_ noisy at the high end of the band. As for power line noise & such, that's rarely a problem.

I recently pulled a salvaged 15 volt 4 amp linear power supply out of the garage, tweaked it down to 13.8 vdc and set up a spare transceiver with it for casual RX. I had a constant electric motor (impulse) type noise in the RX that was particularly strong on the lower bands. Played with the antenna, played with the location, but couldn't get rid of the noise. Then I fired up the rig with no antenna connected. Still there at a righteous S-8 in the AM broadcast band.

Lesson Learned: Not all regulated power supplies are clean enough for radio use, even if they look like a high-dollar piece with an oversized transformer and a 723 precision regulator chip driving a pair of 2N3055's. Nice, beefy, power supply, but noy-zee!
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Never change a password on a Friday                
WB6BYU
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Posts: 13336




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« Reply #9 on: June 01, 2001, 02:12:33 PM »

Make a directional loop antenna and connect it to your rig.  Use it
to sniff out the noise.  (Do the trick with the circuit breakers first to
see if it is being generated inside your house or outside.)  Use a
6m or 10m mobile rig to drive around the neighborhood if needed.
We just tracked down some noise affecting 40m and 2m (among
other bands) which was radiating along the power lines from a
source a couple blocks away.
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RobertKoernerExAE7G
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Posts: 1435




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« Reply #10 on: June 02, 2001, 04:23:06 AM »

Let us know what you try and what happened.

One of the best ham books I've come across is ON4UN's, "Low Band DXing".  It is a great antenna book, and it goes into grey line pretty good.  

I still here one of the people in 6 land that is mentioned as a pioneer 75 meter grey line DXing.

You'll probably find this site fascinating: http://solar.spacew.com/www/160gray.html

It shows The Grey Line in real time, and it shows world wide MUF.

This month's QST has a nice how to article on delta loop beams.

Have FUN
Bob
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N3WWN
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Posts: 9


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« Reply #11 on: June 04, 2001, 03:14:47 PM »

It seems most of my noise is between 50.0 and 51.5 MHz.

The noise is not seen on the 10m, 12m, or 15m with the same radio.

I bought a nice gell cell from a hamfest this weekend and disconnected my home built power supply and powered the radio off the battery alone.  There was no change in noise level before or after switching to battery only.

I have disconnected the tuner and the (pre)amp and ran the antenna directly into the radio...no change in noise level.

Changing to AM during periods of extreme interference has not produced any sort of hum or cylcic sounds that I can determine.  The change in sound is the same as changing from SSB to AM when the noise floor is very low.   Just static.

The only thing that has decreased my noise floor so far is to disconnect the antenna.  Even with my power supply connected, if the antenna is disconnected, there is no noise.  (No noticible needle movement above zero).

AE7G, you gave me a list for a "near-realtime greyline map."  That is the map I was looking at when I figured I was working greyline. *grin*

By looking at that map and sunset times, I was able to predict when the band was going to open and close to within about 10 or 15 minutes each day for 4 days.    

So, what I was thinking is that since the sun was setting on the D layer, which dissipates quickly, and that it would take slightly longer to set on the E layer, which dissipates a little slower than the D, along with the distances heard/worked, that E Skip was being generated at the grey line.  

I was calling this "greyline propagation" when it may actually be called something else.  Please excuse my ignorance. hi hi  
This is my first summer working anything besides 2m (due to monetary conditions and my first summer outside of a filing cabinet apartment building)

Thanks again for all the information, advice, and help!

73,

-Rich
 N3WWN
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RobertKoernerExAE7G
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Posts: 1435




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« Reply #12 on: June 06, 2001, 03:55:47 AM »

Hi Rich.
I only play around on HF.
When I've had HF noise problems, I was able to aim my antenna and find a direction for the noise.  The noise appeared on all bands.

With your gell cell, you should be able to run your rig mobil.  You can stick solid, stiff wire into your rig's antenna connector as a vert, or run stranded wire hung onto a coat hook as a vert in your car.  Make sure you cannot accidently xmit with an antenna like those.  that should get you out driving around to see if the noise gets stronger or weaker away from your house.

Another temp antenna is to use zip cord.  Tie a knot in it, trim it to go from the inside roof of your car to your rig; solder a PL259 onto it; unfold the other end after the knot so that you have a dipole and sling it in your car, with any excess haging out the windows, or taped to your roof.  Nice easy mobile directional set up that way.  Zip cord set up that way is supposed to be around 75 ohms; so, you can make a quick easy diople with it -- need to trim the lengths if you want to xmit.

The only time I've encountered mention of grey line propagation is for 40, 80 and 160.

Pretty good that you can predict 6 meter prop!  By looking at the MUF contours, you can see where 6 meters can carry your sigs to.

Have FUN
Bob
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