I often get extended periods of precipitation static which raises the noise floor by 20 to 30dB, it also produces a very odd "screaming" sound when listened to using AM demodulation.
Download and change the attached file .txt extension to .mp3 to hear an example.
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I think the actual noise source is St Elmos fire (plasma discharge) on a nearby metal tower. The pitch of the "screaming" changes when there is a nearby lightning strike, which makes me think that it modifies the local electrostatic field.
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pretty common in dry / dusty climates. Here in NE USA it can occur on a dry cold snowy day. A simple 1Mohm bleeder on any antenna without a DC path is enough.
In my case, the antennas have static bleed resistors, but I don't think the "screaming" noise is being locally generated on the antenna or mast. I suspect it is some form of plasma discharge occurring on a much bigger tower that is nearby.
I do also hear the sizzling & white noise that is produced by dry air or charged dust particles, as you describe, and usually without rain or lightning being present. I think that is being directly transferred to the wire antenna. But it tends to sound different, with no "screaming" or changes in pitch, when there is a nearby lightning burst.
The only benefit of bleed resistors is that you don't get the gradual build up of a static charge, and a sudden discharge when it finds somewhere to flash over. If you have a coax connector on a long wire antenna, you can often hear a tick, tick, tick, as it arcs between the centre conductor and grounded screen. However, fitting bleed resistors doesn't stop the static induced noise from occurring.
FYI - the weather has turned to rubbish here. Raining, cool and thundery.
The big green line across the band was the lightning with lots of static discharge from many smaller strikes around the area. We tend to get a lot of sheet lighting here and not so much fork.
Fortunately I also have a galvanic isolating transformer inline with the antenna which claims to protect the receiver from electrostatic discharges too.
Very interesting topic. My KiwiSDR #2 is in a region of France where thunderstorms are frequent (Périgord, Dordogne valley, Nouvelle Aquitaine). And the antenna is vertical, 11 meters, isolated from the ground (radiating pylon)... I placed a 0.5 A fast fuse at the bottom of the antenna. The electrostatic charge is so strong, that I often find it blown! Fortunately, I have several high-performance surge protectors of different types, two at the bottom of the antenna, two others at the arrival of the 250 meter long coaxial cable. There is also a first Unun transformer at the start, and a second at the arrival.
When the long coaxial cable arrived, just before the RF amplifier, I built myself a protection box which contains: a discharge coil, a 0.5 A fast fuse, protection diodes PR1007G in parallel, a serially wired robust capacity. The PR1007G diodes can handle peak currents of 30 A (Non-Repetitive Peak Forward Surge Current 8.3 ms). Their capacitance is 8 pF. It's simple and effective. Here is the picture :
Currently, I am improving the ground plane of the antenna, by spreading cat litter. It is clay, a material that retains water, which is called Bentonite (grey calcium bentonite clay). To improve it further, I need to find graphite in small pebbles.
Comments
I often get extended periods of precipitation static which raises the noise floor by 20 to 30dB, it also produces a very odd "screaming" sound when listened to using AM demodulation.
Download and change the attached file .txt extension to .mp3 to hear an example.
I think the actual noise source is St Elmos fire (plasma discharge) on a nearby metal tower. The pitch of the "screaming" changes when there is a nearby lightning strike, which makes me think that it modifies the local electrostatic field.
St. Elmo's fire - Wikipedia
https://en.wikipedia.org/wiki/St._Elmo%27s_firePecipitation Static or P-static
https://www.w8ji.com/pecipitation_static.htmRegards,
Martin
pretty common in dry / dusty climates. Here in NE USA it can occur on a dry cold snowy day. A simple 1Mohm bleeder on any antenna without a DC path is enough.
In my case, the antennas have static bleed resistors, but I don't think the "screaming" noise is being locally generated on the antenna or mast. I suspect it is some form of plasma discharge occurring on a much bigger tower that is nearby.
I do also hear the sizzling & white noise that is produced by dry air or charged dust particles, as you describe, and usually without rain or lightning being present. I think that is being directly transferred to the wire antenna. But it tends to sound different, with no "screaming" or changes in pitch, when there is a nearby lightning burst.
The only benefit of bleed resistors is that you don't get the gradual build up of a static charge, and a sudden discharge when it finds somewhere to flash over. If you have a coax connector on a long wire antenna, you can often hear a tick, tick, tick, as it arcs between the centre conductor and grounded screen. However, fitting bleed resistors doesn't stop the static induced noise from occurring.
Regards,
Martin
FYI - the weather has turned to rubbish here. Raining, cool and thundery.
The big green line across the band was the lightning with lots of static discharge from many smaller strikes around the area. We tend to get a lot of sheet lighting here and not so much fork.
Fortunately I also have a galvanic isolating transformer inline with the antenna which claims to protect the receiver from electrostatic discharges too.
Anyway, its fascinating stuff.
Happy New Year to all,
Very interesting topic. My KiwiSDR #2 is in a region of France where thunderstorms are frequent (Périgord, Dordogne valley, Nouvelle Aquitaine). And the antenna is vertical, 11 meters, isolated from the ground (radiating pylon)... I placed a 0.5 A fast fuse at the bottom of the antenna. The electrostatic charge is so strong, that I often find it blown! Fortunately, I have several high-performance surge protectors of different types, two at the bottom of the antenna, two others at the arrival of the 250 meter long coaxial cable. There is also a first Unun transformer at the start, and a second at the arrival.
When the long coaxial cable arrived, just before the RF amplifier, I built myself a protection box which contains: a discharge coil, a 0.5 A fast fuse, protection diodes PR1007G in parallel, a serially wired robust capacity. The PR1007G diodes can handle peak currents of 30 A (Non-Repetitive Peak Forward Surge Current 8.3 ms). Their capacitance is 8 pF. It's simple and effective. Here is the picture :
For further information, the description of the installation : http://labroue.autreradioautreculture.com/Courdilles/KiwiSDR/Documents/Description_KiwiSDR_Tremolat.pdf
We have another phenomenon in our area : les Farfadets. It's visually stunning. Nicolas Escurat photographs them :
Farfadets : https://www.facebook.com/share/r/18QBqRmqLb/?mibextid=wwXIfr
Best regards, Philippe
wow - thats an impressive radio set up.
and wow - those Farfadets are impressive too. I suspect they make one heck of a lot of RF scatter across the entire spectrum with a lot of energy.
Dear smg, thank you very much, it's a pleasure.
Currently, I am improving the ground plane of the antenna, by spreading cat litter. It is clay, a material that retains water, which is called Bentonite (grey calcium bentonite clay). To improve it further, I need to find graphite in small pebbles.
Best regard, Philippe