The AM Forum

...with the poor weather, lots of blowing snow out there...
..what might be opinions on snow static, how it is produced, voltages, etc...
..i'm sitting here, blowing snow outside, and SNAP-SNAP-SNAP...coming from my open wire feeders...
..any thoughts?...

..sk..

Had that here this morning...

Nice SNAP from the receiver, enough to shut it off!
(it's a software defined 'QS1R'...)
The software locked up.... made me a little nervous...
Thought I'd have to get the soldering iron out..
But after a reboot, all was well....


Snow-static...

Caused by the snow rubbing by the antenna..
Just like scuffing your feet across a rug, or a wimshurst machine etc...
The snow developes a charge as it falls through the air, and gives up it's charge to the antenna on it's way by...

Voltages can be quite high.. 1 to 3 kv easily, depending on the smallest gap it can jump in your antenna system..... the smaller the gap, the smaller charge that can build up.

KF1Z is right, very common here in the Northeast, my elmer, W2UJR, used to report it, and I hear it during most storms.

It sounds like popcorn popping, a rapid series of snaps in the speaker, the frequency of which varies with the intensity of the snow. Here on the coast, it does seem more prevalent, or at least noticeable, on the higher bands, 160 and 75 meters. I find the noise blanker largely takes care of it, which makes sense, for the audio characteristic is much like a spark plug firing.

Right now we're in the middle of a another Nor'Easter, have not checked the bands yet, but sure it is there.

Can be severe enough to damage equipment, in fact has been blamed for some aircraft losses...back in 1937.
Interesting article on snow static right here -->http://www.time.com/time/magazine/article/0,9171,770673,00.html
Text below:

"A major factor in last winter's airplane crashes was radio failure due to snow static. United Air Lines therefore set aside a Boeing laden with instruments and experts which flew almost daily over the mountainous Northwest—an ideal snow-static laboratory. Snow static was supposed to be caused by impact on the antenna of droplets containing tiny electric charges. United last week announced that it is caused by discharge from trailing edges of electricity gathered while flying through heavily charged clouds. When sufficiently severe, snow static affected the shielded loop, heretofore the best-known remedy (TIME, Jan. 25), as much as any antenna. The remedy worked out by United is to trail from the tail 50-, ft. of insulated wire, an electric suppressor and 50 ft. more of naked wire. The electricity flows off the naked wire, making static so remote from the antenna at the plane's nose that radio reception is not impaired."

I don't have a problem with it on my horizontal loop (fed with coax and thus at DC ground) but I used to have a problem with it when I used a dipole.  I wonder if you put an RF choke to ground (as is suggested by the makers of most all band verticals) if that would take care of the problem?  I have never noticed snow static with my Hy Gain Hy Tower (which I also use on 160 fed as an inverted L); it does have the recommended RF choke to ground.

Rodger WQ9E

Precipitation static usually sounds like a snare drum in the AM receiver.  Each little charge on the raindrops or snowflake causes a discharge to the antenna when they strike the wire.  Besides this noise, there can be a net build-up of dc voltage on the antenna system if it floats (accumulated charge).   

I used to get break-downs in my Drake R-7 input circuit when there was a thunder storm approaching.  Presently, I have a 220 Ohm resistor across the receiver side output of my coaxial antenna relay (center to gnd).  A parallel choke will do the job too.  I do listening at very low frequencies so prefer the resistor over a choke.   This will keep the voltage from building up until there is a breakdown in your radio.  But the snare drum sound you can’t get rid of, I don’t think.

Most receivers have a low resistance dc path to ground on the input but obviously not always.  Everyone should check for this.  Some antenna matching networks will create a dc path to ground also.

Another phenomenon I have not heard until the last few months is very similar to normal precipitation static but I believe occurs at a much higher rate, so frequent that it sounds almost like white noise.  I went outside and much to my surprise there was no precipitation.  I believe that this is precipitation static occurring up in the atmosphere.  This involves many more particles than what strikes your antenna.  When it occurs, it may be happening over a large geographic area and possibly radiating very far, because one time when this was going on here, I heard Tim WA1HLR complain of the same thing!

So I put the same lash up on my house chimney mast or free standing tower and hope the blizzard blows at least 50 mph?  :o

Either that or put my house on wheels and get a couple of strappin' Evenrudes with props replacing the screws..

Might work. 

Tom WA3KLR Said,


I use a hefty RF choke (inductor) on each legs of my 600 feed line. No snow or wind static what so ever.

Mike

Don't remember if this was recommended for this particular problem or not, but I recal someone talking about a 1meg or higher resistor from some point in the Ant system to ground to bleed of the static buildup.  That might have been for receive only systems though.

My first experience with this phenomenon was back when I was a young JN of about 13. I had my station in a closet in my bedroom and had the coax from my 20 meter GP up on the roof going to one side of a DPDT knife switch (the other side was my 40 meter dipole). I couldn't afford coax switches back then - could barely afford PL-259's!!
One dry cold winter night, the wind kicked up and I kept hearing something snapping in my closet. Turned out that as the charge would build up, it would arc across the switch poles to the ground side.
I had never witnessed this before and it scared the crap out of me as I lay there in the dark wondering how to make it stop. Never thought to just ground it but I think I was afraid to touch it.

I heard the snapping inside my Matchbox this evening, so I broke out the video camera.

Couldn't resist getting some live feed of the arcing going on on the feeders.
Nor could I resist touching it, ouch! like a spark plug wire.
Not going to be good going into any solid state device, unless there is a path to ground.

Needless to say, you'll be suitably impressed with the arc and the corresponding discharge and glow in the neon bulbs.

I'll be posting a link to it soon, uploading now.

Dave/W3PN Said,


That struck a nerve. I grew up with 3 brothers and a sister. Personal space didn't exist in our house. My bedroom at age 11, 1962, was shared by all of the boys, two bunk beds. The closet served as my radio room. An S-38 and an Allied CB HT.

My co conspirator lived a block away. In that space a lifetime radio hobby rooted. Mostly listening late at night to foreign broadcast and hams. Admittedly, many Detroit Red Wings games enjoyed as well.

Mike

Snow Static Video at W1UJR - Taken this evening during Nor'Easter snow storm.

http://www.youtube.com/watch?v=_7HSTPl6e-I

Excellent Bruce!!! That is exactly the way it sounded back in '61 or so.

Nice video.


Mike - I shared my bedroom with my younger brother.

..good story mike, until the reference to the  "dee-troilet dead things"....

..sk..

  p.s.   blue and white forever 

Mike,
you might consider a spark gap in parallel with the RF chokes.

The vacuum spark gap tubes are inside the gray box in the center. That lightening suppressor came with a ferrite core transformer on each side of the feeders inside the gray box. The box is made by ICE Products (Industrial Communication Engineers LTD) and sold by Array Solutions in Sunnyvale, Texas and is "RATED" for 4KW.

The first one lasted one transmission on AM at legal power. I sent it back and received another which also failed in a flash. After calling Array Solutions I opened up the box and found both transformers smoked.

John at Array Solutions sent me the inductors shown in the picture at no charge. I removed the ferrite's and moved the terminals to the exterior. It worked out fine in the end.

Mike

Nice video Bruce. I was hearing it like fury here on Friday and also yesterday throughout the evening during the second storm. As previously mentioned, it sounded very much like popcorn. As expected, no sign of it at all on the tuned loop which is currently residing in the garage.

Rob W1AEX