rain QRN? - elmers Forum at eHam.net

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rain QRN?	Reply
by M5AEO on November 22, 2009	Mail this to a friend!
I have noticed that when it rains I experience interference on HF reception in the form of 'crackling', just like electric motor noise. I was wondering if this is caused by rainfall? Perhaps the rain drops become electrically charged as they fall through the troposphere and then discharge when they come into contact with the antenna element? Is this theory possibly true or is it just conincidence?

RE: rain QRN?	Reply
by K6LO on November 22, 2009	Mail this to a friend!
The rough cut top of my 75 meter vertical would exhibit faint corona discharge during windy summer storms until I solder a cap on the top of the tubing. Does your antenna have any sharp edges?

RE: rain QRN?	Reply
by K6LO on November 22, 2009	Mail this to a friend!
And your post has me reminiscing of a funny event a friend and I experienced traveling down Interstate 5 about twenty five years ago. It was late at night. We were operating 160 mobile with a Yaesu FT-901DM on the floor of the car (HF mobile was different then) and an old Heathkit HA-14 tube amp in the trunk. These were feeding a very tall, helical antenna. On voice peaks the antenna would come alive with corona discharge. This prompted a very curious Highway Patrolman to stop us and ask, "What's THAT!!!" Um uh, well, we're hams... and...

RE: rain QRN?	Reply
by W4VR on November 22, 2009	Mail this to a friend!
Rain itself does not cause static. The static you're hearing is more likely caused by a potential difference between the ground and rain clouds. On the other hand, snow flakes pick up a charge as they form and fall, and when they strike your antenna, they discharge. You hear this discharge as static in your receiver.

RE: rain QRN?	Reply
by W5DXP on November 22, 2009	Mail this to a friend!
I experienced precipitation static during dust storms in AZ - worst case caused actual arcing across the coax connector which scorched my shag rug. Some have reported p-static from snow and rain. Some, who have never experienced it, deny its very existence and/or try to blame corona discharge. http://www.its.bldrdoc.gov/fs-1037/dir-028/_4096.htm More info available on the web. Some hams install a high-ohm resistor, choke, or 4:1 voltage balun across their feedpoint terminals to discourage the p-static buildup. Closed-loop antennas don't have the static buildup problem. -- 73, Cecil, w5dxp.com

RE: rain QRN?	Reply
by K4SAV on November 22, 2009	Mail this to a friend!
Anyone with a Yagi on a tower in an area that has lots of rain can tell you of experiences with rain static. When I lived in Florida I had many opportunities to drive home in the rain, since that was the normal condition in the summer months. On many occasions I would experience the effects of charged rain drops. That didn't always happen with rain, but it happened maybe once a month. When that happened the noise level became a function of car speed, maybe S4 noise at 20 mph and S9+30 at 70 mph. The faster speed hits more raindrops. That was on HF. I have also experienced the effect mentioned by W4VR, due to charge difference between the clouds and ground. That produces a small corona on the antenna. That is a different phenomenon and the observed effects are very different. The noise level was no longer a function of car speed. Jerry, K4SAV

RE: rain QRN?	Reply
by N7DM on November 22, 2009	Mail this to a friend!
Rain Static is real, and is a common thing here in the Northwest. The only solid solution I have ever found is to use D.C. closed antennas as much as possible, such as Loops or Folded Dipoles. dm

RE: rain QRN?	Reply
by N7DM on November 22, 2009	Mail this to a friend!
Rain Static is real, and is a common thing here in the Northwest. The only solid solution I have ever found is to use D.C. closed antennas as much as possible, such as Loops or Folded Dipoles. dm

RE: rain QRN?	Reply
by W5WSS on November 22, 2009	Mail this to a friend!
Yes rain static is real. I experienced it daily in south Florida. I am not suggesting that south Florida rain drops are super charged however:) I experienced rain static noise on the yagi that used a Gamma match at the feed point.Not on the quad but On the quad a more dangerous symptom perhaps, was an arcing of static discharge found at the station coaxial feedline from the antenna strong enough to jump to ground from several inches removed.On a different and more serious note The most impressive symptom is when a static build-up begins with a clik clik clik then speeds up to a steady state buzz at +30db time to disconnect the feedline because there is going to be a nearby lightning stroke.

RE: rain QRN?	Reply
by M5AEO on November 22, 2009	Mail this to a friend!
Fascinating discussion! Many thanks. M5AEO

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