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#1
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Cecil Moore wrote:
gravity wrote: i guess my main point is we need to define "clear weather charged particle noise". It's what happens when the wind blows in the Arizona desert when the humidity is low and there's not a cloud in the state. There are hundreds of reports on the web of such a phenomenon. Example: http://www.eham.net/forums/Elmers/83174 -- 73, Cecil http://www.qsl.net/w5dxp And it happens in inland Southern California with Santa Ana winds. -- Jim Pennino Remove .spam.sux to reply. |
#3
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wrote:
wrote: Cecil Moore wrote: gravity wrote: i guess my main point is we need to define "clear weather charged particle noise". It's what happens when the wind blows in the Arizona desert when the humidity is low and there's not a cloud in the state. There are hundreds of reports on the web of such a phenomenon. Example: http://www.eham.net/forums/Elmers/83174 -- 73, Cecil http://www.qsl.net/w5dxp And it happens in inland Southern California with Santa Ana winds. -- Jim Pennino ....and it happens here in humid Georgia, and in dry Georgia, and in Ohio in summer and winter. There doesn't need to be a particle in sight. I can go outside and float the feeder of my long 160M dipole that is 300 feet high. The whack will knock you right on your rump. But that charge is actually pulling the antenna CLOSER to the potential of the air around the antenna. When I ground that antenna so the antenna moves to earth potential, the corna from that antenna actually gets worse....not better. The reason is pretty simple. The earth is a big charge sink, and is really at considerably different potential than the air at 300 feet even on a clear calm day. A little wind helps quite a bit, pushing charged air past the antenna and increasing the charge rate. What most people miss is that it is the difference in potential between earth (or lower heights) and the air around the antenna that causes the leakage currents. The wind simply increases the problem. 73 Tom Umm, no, two different things. If it were charge building somewhere and discharging it wouldn't have the characteristics it does, which is random, continuous, of extremely short duration, and at a very high rate. When it gets bad, it is quite visible as very random "snow" on TV channels 2 through 4 on an otherwise perfect picture. The snow is spots of extremely short duration. Arcing (my neighbor has an arc welder so I have something to compare it to) shows up as lines. When watching TV while he is welding it is very obvious from the visual "noise" when he trying to start an arc on some rusty thing versus an established arc from the length of the visual "noise". This particular effect ONLY happens during low humidity on very windy days. The intensity of the snow changes very little with wind speed, the duration not at all, but the rate changes drastically. I took all the electromagnetic courses to get my BSEE and I'm a pilot, so yes, I know about corona. -- Jim Pennino Remove .spam.sux to reply. |
#4
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wrote:
When it gets bad, it is quite visible as very random "snow" on TV channels 2 through 4 on an otherwise perfect picture. The snow is spots of extremely short duration. So one can see the individual charged particles even if one cannot hear the individual charged particles. That makes a lot of sense. I wish I had thought to hook my antenna up to my TV while the charged particle problem was occurring. -- 73, Cecil http://www.qsl.net/w5dxp |
#5
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Cecil Moore wrote:
wrote: When it gets bad, it is quite visible as very random "snow" on TV channels 2 through 4 on an otherwise perfect picture. The snow is spots of extremely short duration. So one can see the individual charged particles even if one cannot hear the individual charged particles. That makes a lot of sense. I wish I had thought to hook my antenna up to my TV while the charged particle problem was occurring. -- 73, Cecil http://www.qsl.net/w5dxp Well, at this point I wouldn't bet the farm on the base cause being charged partcles impacting the antenna, but if it walks like a duck and quacks like a duck... However, for this particular effect it is obvious that it is quantized and that the rate of generation is directly proportional to the wind speed. Since there is nothing in the air large enough to be visible, it would seem reasonable that whatever is delivering charge to something is dust particles. The number of dust particles in the air is also directly proportional to the wind speed, lending further credence to the theory. As to how to test the theory, fooling around with the TV antenna on the roof with 40 to 60 knot gusts isn't going to be done by me no matter how much beer you provide. One thought would be to make a pair of channel 2 dipoles with one inside a non-conducting dust cover. Put the two antennas side by side and compare the results seen on the TV screen. Another experiment would be to build a full sized dipole and a shortened loaded dipole for channel 2. If the effect is caused by particles impacting the antenna, the quantity of snow would be proportional to the antenna sizes. It would be interesting to see what happens. In any case, Santa Ana winds don't normally appear this time of year, so there are about six months to come up with a definative experiment. And yes, if it is simple and cheap enough, I'm willing to do it. -- Jim Pennino Remove .spam.sux to reply. |
#6
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wrote:
Since there is nothing in the air large enough to be visible, it would seem reasonable that whatever is delivering charge to something is dust particles. Unfortunately, one poster here apparently thinks if he cannot see it, it doesn't exist. Presumably, if he ever goes blind, even his ham transceiver will cease to exist. :-) He reminds me of a governmental expert who said yesterday on Foxnews: Since the successful kill rate for our anti-ICBM missiles is 60%, we have to fire two of them to be sure we shoot it down. :-) (After all 60% + 60% = 120% and wouldn't that be overkill?) :-) And yes, if it is simple and cheap enough, I'm willing to do it. I indirectly performed experiments in curing my arcing problem. I replaced the bare wire with ordinary 600v insulated wire. It reduced the problem considerably but didn't cure it. I then found an antenna wire called "quietflex" at a hamfest that has 1000v insulation. To the best of my knowledge, that cured the problem. There is apparently a thickness of insulation that prohibits the transfer of charge from dust particles. -- 73, Cecil http://www.qsl.net/w5dxp |
#7
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He reminds me of a governmental expert who said yesterday
on Foxnews: Since the successful kill rate for our anti-ICBM missiles is 60%, we have to fire two of them to be sure we shoot it down. :-) (After all 60% + 60% = 120% and wouldn't that be overkill?) :-) 84%. the "expert" might borrow a copy of Innumeracy. the astute reader will note that this figure may not work in the real world. Gravity |
#8
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The thickness of insulation on an antenna wire does not entirely
reduce noise due to (charged particle) precipitation. There are two capacitances involved - the self-capacitance of individual isolated particles and the much greater capacitance of the insulating material between its surface and the wire. When it impacts with the thick insulation, the electric charge on a particle redistributes itself between antenna capacitance and particle capacitance. Only a very small fraction of particle volts is transferred to the antenna via antenna capacitance. The result is a reduction in receiver noise. For given particle volts, size of particle, thickness of antenna wire insulation, permittivity of insulation, the noise induced in the receiver is calculable. As Roy would insist on, to prove the point, all you have to do is measure the average volts on a particle of average diameter. And the best way of doing that is to work backwards from the S-meter. ;o) A nice, low noise antenna can be constructed by removing everything from the inner conductor of a 1" diameter coaxial cable except the solid polyethylene insulation. This is an expensive operation, likely in the UK to of use only for 15 minutes every few years. So nobody bothers. ---- Reg. |
#9
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Unfortunately, one poster here apparently thinks if he cannot
see it, it doesn't exist. in my country, people say in land of blind one eye man is king. Soong |
#10
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Dear Jim Pennino WB6DKH:
Well said, and yet here we are over 100 messages latter (even with a Cecil filter) with strange contentions still going on. It has become apparent that this is a religious debate and it is time for additional filtering. To supplement my message of June 7, 2006: One should provide continuity to earth from as many elevated conductors as possible. It is sometimes difficult to do this with guy wires that are "broken up" with insulators. Location is an important factor with respect to which local, non-man-made noise sources dominate. In Toledo, Ohio and Georgia it might be one thing and in the Arizona desert quite a different thing. Time and local weather is also an important factor. Lighting discharges off of, or towards, an antenna will dominate everything else. Having spent the last 73% of my life in an academic setting involving science and engineering where orthodoxy applies only (temporarily) to verified physical laws, I now understand why wars are fought over which end of the egg is cracked first. It has rounded out my education. As Roy has pointed out: it important to observe to the readers who are not participating that they should filter what they read with care. Thank you Jim for interjecting your experience. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: snip Umm, no, two different things. If it were charge building somewhere and discharging it wouldn't have the characteristics it does, which is random, continuous, of extremely short duration, and at a very high rate. When it gets bad, it is quite visible as very random "snow" on TV channels 2 through 4 on an otherwise perfect picture. The snow is spots of extremely short duration. Arcing (my neighbor has an arc welder so I have something to compare it to) shows up as lines. When watching TV while he is welding it is very obvious from the visual "noise" when he trying to start an arc on some rusty thing versus an established arc from the length of the visual "noise". This particular effect ONLY happens during low humidity on very windy days. The intensity of the snow changes very little with wind speed, the duration not at all, but the rate changes drastically. I took all the electromagnetic courses to get my BSEE and I'm a pilot, so yes, I know about corona. -- Jim Pennino |
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