Noise buildup throughout the day, gone at night. any ideas?

[tchr01]

I seem to be the noise captain around here! I'm getting this steady pattern of noise that seems to build louder and louder during the day up to S9, and then around when the sun starts to go down it dissipates. At night its totally gone.

I went out in the yard with my shortwave tuned to 27.135, and the antenna extended. As soon as I got near my antenna (feed line and right under it), the same noise appears as it does on my CB. Same pattern, same sound. When I move maybe 20ft away from my antenna mast (its up on a shed), the noise is gone. When I move near my house, the noise is gone. I even checked out my electric service meter and exterior GFCI outlets.. Is my antenna just a magnet for RFI?

Uniden 980SSB
100ft RG8X
Inverted Vee Dipole 1/2 wave about 21ft up on an aluminum/fiberglass painters pole type mast (great SWR)

Thanks!!

Wednesday at 9-24 AM.mp3

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[brandon7861]

I definitely hear a power line type noise in there. When insulators or grounding hardware begin to arc, it is usually intermittent depending on humidity and dew point. When the sun is up, the moisture on the arcing part can evaporate and that allows arcing. When it is moist, the arc problem goes away. At night, the temp probably drops enough to reach the dew point which wets the arc path and stops it.

Even though you have a great SWR and the problem is probably with the grid hardware, I would still check to make sure the coax is not part of the antenna as vertical elements pick up this noise better. An easy way to do that is to add a 1/4 wavelength jumper to change the coax length. If the SWR changes, the coax is acting as part of the antenna and could be what is picking up most of the noise. Is there a balun at the antenna?

Power line noise is a tough one to deal with. If you call to have the electric company come investigate, try to pick a warm dry day with low humidity to ensure the problem is there for them to find.

 

[tchr01]

I definitely hear a power line type noise in there. When insulators or grounding hardware begin to arc, it is usually intermittent depending on humidity and dew point. When the sun is up, the moisture on the arcing part can evaporate and that allows arcing. When it is moist, the arc problem goes away. At night, the temp probably drops enough to reach the dew point which wets the arc path and stops it.

Even though you have a great SWR and the problem is probably with the grid hardware, I would still check to make sure the coax is not part of the antenna as vertical elements pick up this noise better. An easy way to do that is to add a 1/4 wavelength jumper to change the coax length. If the SWR changes, the coax is acting as part of the antenna and could be what is picking up most of the noise. Is there a balun at the antenna?

Power line noise is a tough one to deal with. If you call to have the electric company come investigate, try to pick a warm dry day with low humidity to ensure the problem is there for them to find.

Ah ok this is interesting. It is raining right now and the issue has been much less today. Still there now I can hear it but its def not hit near s9 today. Just under S5 when it comes up.

No balun, just a center PVC insulator. I have wire attached to the outside of the connector that runs down next to the coax to a rod below the antenna. Trying and dissipate some of the noise.

Would trying to air-wind a choke balun help here? And at what point of the feedline? I think its 5 turns at 4.25inch radius for 27mhz... thanks for the suggestions!

 

[brandon7861]

Ah ok this is interesting. It is raining right now and the issue has been much less today. Still there now I can hear it but its def not hit near s9 today. Just under S5 when it comes up.

No balun, just a center PVC insulator. I have wire attached to the outside of the connector that runs down next to the coax to a rod below the antenna. Trying and dissipate some of the noise.

Would trying to air-wind a choke balun help here? And at what point of the feedline? I think its 5 turns at 4.25inch radius for 27mhz... thanks for the suggestions!

I would put the balun right at the antenna if possible. Having it there not only stops the transmitted signal from getting onto the shield, but it also stops signals the coax shield picks up from finding its way up to the open end and into the coax. That wire running down likely adds to the imbalance. Try the choke balun right at the antenna and remove the wire hanging down. You want both sides of the dipole to be the same electrically. If you want the coax shield at ground potential, ground the radio. I can almost guarantee that making these changes will affect the SWR. You should not let that deter you from making the proper adjustments. Once you have the antenna system balanced and no RF on the shield, then retune the antenna by evenly adjusting the element lengths.

I doubt this will eliminate the noise but it would probably reduce it. Removing the imbalanced aspects from the antenna will also clean up the antenna's RF pattern and improve signals.

I do not know the size of the coil you should wind, but it is worth experimenting. But to prevent failure here from discouraging you, I'll add what I have discovered. In my mind, the size and number of turns of coax depends on what the impedance is looking down the common-mode path toward the radio. Remember, this path is an antenna and antennas have feed point impedances. For example, if that particular length of shielding offers a capacitive reactance looking away from the antenna and down the outer shield, inductance from a coiled up coax balun could cancel it and make things worse. This is not always the case, but it happens. It all depends on how long the coax is, if the radio is grounded, what the coax is near, etc. There is no formula to determine this. I believe this to be the reason there is no definitive instructions on "ugly baluns". There is also a fine line between enough winding and too much as eventually the inter-winding capacitance can create a resonance or completely overtake the inductance. Sometimes they work great, other times not so much.

If the more typical recommendations for winding the air choke don't work, simply grounding at the radio or changing the length of the coax might change things. What I have done in the past is to disconnect the antenna from the coax, but keep the coax hanging in the same spot. I then do an OSL calibration to the end of the coax with the VNA to set the reference plane. I then connect a crudely made, unshielded 50Ω termination (not the shielded one used for OSL calibration) and measure the impedance again. Any deviation from 50Ω represents the common-mode impedance being in parallel with the 50Ω (unshielded) load. If, after calculating out the 50Ω, what remains is capacitive, I change the length of coax so that the impedance is moderately inductive, then I add the choke balun windings at the antenna end until I get as close to 50Ω as I can signaling the shield is no longer part of the system. This is a long process, but I found it well worth my time.

Edit: radiation from the antenna can also couple to the coax shield, so it is a good idea to keep the feed coax as close to perpendicular with respect to the antenna as possible.

 

[tchr01]

I would put the balun right at the antenna if possible. Having it there not only stops the transmitted signal from getting onto the shield, but it also stops signals the coax shield picks up from finding its way up to the open end and into the coax. That wire running down likely adds to the imbalance. Try the choke balun right at the antenna and remove the wire hanging down. You want both sides of the dipole to be the same electrically. If you want the coax shield at ground potential, ground the radio. I can almost guarantee that making these changes will affect the SWR. You should not let that deter you from making the proper adjustments. Once you have the antenna system balanced and no RF on the shield, then retune the antenna by evenly adjusting the element lengths.

I doubt this will eliminate the noise but it would probably reduce it. Removing the imbalanced aspects from the antenna will also clean up the antenna's RF pattern and improve signals.

I do not know the size of the coil you should wind, but it is worth experimenting. But to prevent failure here from discouraging you, I'll add what I have discovered. In my mind, the size and number of turns of coax depends on what the impedance is looking down the common-mode path toward the radio. Remember, this path is an antenna and antennas have feed point impedances. For example, if that particular length of shielding offers a capacitive reactance looking away from the antenna and down the outer shield, inductance from a coiled up coax balun could cancel it and make things worse. This is not always the case, but it happens. It all depends on how long the coax is, if the radio is grounded, what the coax is near, etc. There is no formula to determine this. I believe this to be the reason there is no definitive instructions on "ugly baluns". There is also a fine line between enough winding and too much as eventually the inter-winding capacitance can create a resonance or completely overtake the inductance. Sometimes they work great, other times not so much.

If the more typical recommendations for winding the air choke don't work, simply grounding at the radio or changing the length of the coax might change things. What I have done in the past is to disconnect the antenna from the coax, but keep the coax hanging in the same spot. I then do an OSL calibration to the end of the coax with the VNA to set the reference plane. I then connect a crudely made, unshielded 50Ω termination (not the shielded one used for OSL calibration) and measure the impedance again. Any deviation from 50Ω represents the common-mode impedance being in parallel with the 50Ω (unshielded) load. If, after calculating out the 50Ω, what remains is capacitive, I change the length of coax so that the impedance is moderately inductive, then I add the choke balun windings at the antenna end until I get as close to 50Ω as I can signaling the shield is no longer part of the system. This is a long process, but I found it well worth my time.

Brilliant and practical stuff to try Thanks! Will test some things out.

 

[26OD004]

I'll add what I have discovered. In my mind, the size and number of turns of coax depends on what the impedance is looking down the common-mode path toward the radio. Remember, this path is an antenna and antennas have feed point impedances.

I just wanted to say thank you really, what I quoted above just gave me one of those "why didn't I think of that" moments. It's so obvious now you mention it but, I have never when thinking about feedlines considered the screen between shack and the RF choke/feedpoint to be an antenna itself and present it's own impedance to the bottom of the choke... but of course it is and does!!!

 

[tchr01]

Ok update. It stopped raining! I wound 5 turns of the coax right below the antenna feed point as neatly as I could (not just rando overlapped) and the noise pattern goes from S1-3 instead of S3-5. This seems like a sizable improvement for a few mins up on the ladder. SWR also has no change.

Edit: Also took down my extra wire

If I didn't have that suspected power line buzzing it would be S1 floor no problem. I think we're having more rain for the next few days, but I will see what happens when the sun comes out. A hopeful S3-S5 buzz jump is not ideal, but better than S9.

Im gonna do the battery test as well to double check a pesky outlet or switch in the house isnt causing the pulsing buzz. Thanks again @brandon7861

 

[brandon7861]

When I get power line noise, before anything else, I will walk down the driveway and road with my HT (no fancy directional antenna, just the stock rubber one) lightly rocking each pole or shaking its guy wire. When you find the pole with the problem, the movement will often modulate the noise heard on the HT. Just remember, the poles are all tied together, so shake gently. It really speeds up complaint response time with the electric companies when you can at least tell then what pole the problem is on.

 

[tchr01]

When I get power line noise, before anything else, I will walk down the driveway and road with my HT (no fancy directional antenna, just the stock rubber one) lightly rocking each pole or shaking its guy wire. When you find the pole with the problem, the movement will often modulate the noise heard on the HT. Just remember, the poles are all tied together, so shake gently. It really speeds up complaint response time with the electric companies when you can at least tell then what pole the problem is on.

I did a little more investigation with my shortwave receiver..

Went under 3 poles near by, no noise around them. BUT.. when I got closer to my neighbors house (nearest antenna mount location) it gets louder! I then see a sort of DIY single solar panel on his deck with some wires hanging off about 75ft from my antenna... I gotta ask to see if its hooked up, generating / storing power etc.. This may explain the "at night its quiet" too.. I'm thinking the inverter or storage is suspect?

This neighbor too is doing lots of finishing work in his house, so there is a possibility he has something hooked up weird, running or charging that is creating the buzz. Hes nice so thats good! Will post if I find out if its something nextdoor.

 

[brandon7861]

A ferrite bead order and a case of beer can go a long way

 

[tchr01]

A ferrite bead order and a case of beer can go a long way

Its a great idea. Which mix is best for the ferrite 31?

 

[brandon7861]

Someone else might be better suited to answer that one as I have not done much with RFI. I guess it all depends on what frequencies are on the problematic wires. The only ferrites I've ever bought were supposed to be type 31, but I suspect they are fakes. Lesson learned. I made a simple clamp-on probe for the USB spectrum analyzer. My new plan is to go around measuring everything. Once I know what frequency each wire is carrying, then I will buy ferrites meant for those frequencies from a reputable website. It is something I have not put much time into because my RFI is typically not on the bands I use.

 

[BJ radionut]

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[tchr01]

Did some more investigating. Its not my house, did the breaker test and ran my 980SSB on a battery.

I noticed the noise again on my shortwave when I got under the pole outside my house, and also noticed my SWL long wire also had the same noise running along it. Was sunny today S9+ most of the day, totally unusable. Then around 7pm or so, drops off and now is totally gone. Noise is now below S1 (my new air-wound chokes doing some work for me)...

When I orient myself in a way that the sw radio is in front of me directly, when I turn my back to another pole a few doors down, the noise is gone (my body nulling out the noise im guessing), and when I turn back its back. I also noticed my antenna center feedpoint has a good line of site to the same pole.

Im gonna take a walk over tomorrow with my radio to see what I get. My question would be, could the guy two doors down with new solar be causing RFI back to the pole? Sometimes I wish we all still had analog TV antennas lol.

Here is some afternoon noise pattern. Sometimes it even sounds like five blips in a row fast. https://www.dropbox.com/s/tsjzotqks70s78t/Tuesday at 6-35 PM.m4a?dl=0

 

[tchr01]

One last observation for now, sometimes, the noise gets so aggressive (solid s9) then its just goes away to S1 *poof!* for a few seconds, then creeps back up fast.