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Is It double bazooka less noisy?
Jim Kelley wrote:
Consider the nature of dielectric materials. I could be wrong, but I bet if you stuck a negative oxygen ion on the outside of a jacketed conductor, you could make the conductor inside think you had put an electron directly on it. The question is whether the electron stays on the insulation or migrates through it to the conductor. The size of the charge Vs the dielectric determines how much of the charge actually reaches the conductor. When I went from bare wire to 600v insulation, my precipitation static problems decreased considerably. Then when I went to 1000v insulation and a full wave loop, most of my precipitation static problems disappeared. The worst case of precipitation static seems to be for airplane antennas. Insulation is the recommended cure although folding is also mentioned. Please do a web search for "precipitation static" and see for yourself. http://www.atis.org/tg2k/_precipitation_static.html -- 73, Cecil http://www.qsl.net/w5dxp |
Is It double bazooka less noisy?
Cecil Moore wrote:
Jim Kelley wrote: Consider the nature of dielectric materials. I could be wrong, but I bet if you stuck a negative oxygen ion on the outside of a jacketed conductor, you could make the conductor inside think you had put an electron directly on it. The question is whether the electron stays on the insulation or migrates through it to the conductor. Actually, the question is whether or not one can hear the resulting noise. The size of the charge Vs the dielectric determines how much of the charge actually reaches the conductor. Perhaps you mean the amount of charge Vs. the dielectric determine the voltage. When I went from bare wire to 600v insulation, my precipitation static problems decreased considerably. Then when I went to 1000v insulation and a full wave loop, most of my precipitation static problems disappeared. I see your point. The poorer the dielectric and the greater it's thickness, the lower the induced voltage. There should be some effect, yes. What'd you use, 20 meters of CRT anode wire or spark plug wire? :-) The point with which Tom seemed to take issue was the implication that an antenna with low DC resistance would have lower precipitation static noise. I also disagree with that notion. The worst case of precipitation static seems to be for airplane antennas. Insulation is the recommended cure although folding is also mentioned. Please do a web search for "precipitation static" and see for yourself. http://www.atis.org/tg2k/_precipitation_static.html I'm glad we agree on the definitions. In one of your previous references I noted the term precipitation static used (incorrectly) to describe the noise associated with static discharge. This is a distinction I attempted to point out in my earlier post. Precipitation, among other things, can cause charge to accumulate on objects which are insulated from ground. This accumulation can continue to increase until breakdown occurs, causing a spark and a noise which is big enough to knock down the receiver AGC for a few seconds (or worse). Precipitation static is the noise which is apparent when a relatively high flux of ions impinges upon an antenna. Low DC impedance antennas won't accumulate large amounts of charge or generate a static discharge, but they are nevertheless sensitive to the static noise just as any other antenna would be. In other words, you and Tom W8JI are both right - you just don't know why. ;-) Did you see the article in Harper's magazine on W6AM? Pretty neat. Even that article mentioned precipitation static. 73, ac6xg |
Is It double bazooka less noisy?
Jim Kelley wrote:
Cecil Moore wrote: The size of the charge Vs the dielectric determines how much of the charge actually reaches the conductor. Perhaps you mean the amount of charge Vs. the dielectric determine the voltage. size = amount = magnitude = amplitude. It is hard to visualize how a charge could make it to the conductor without the migration of a quantum particle. The point with which Tom seemed to take issue was the implication that an antenna with low DC resistance would have lower precipitation static noise. I also disagree with that notion. Both of you misunderstood the definition of "noise" that I was using. With the feedline completely disconnected from the transceiver, arcing occurred and that aural noise woke me up at night. It was aural noise from the arcing caused by precipitation static charge tansfer that woke me up and a low DC resistance eliminated it. Precipitation static is the noise which is apparent when a relatively high flux of ions impinges upon an antenna. Low DC impedance antennas won't accumulate large amounts of charge or generate a static discharge, but they are nevertheless sensitive to the static noise just as any other antenna would be. In other words, you and Tom W8JI are both right - you just don't know why. ;-) When a charge hits a closed loop, there are two paths it can take to equalize the charge around the loop. Only one of those paths is through the receiver and that is a higher impedance path than the other path. When a single-wire dipole needs to equalize the charges between the dipole elements, there is only one path available - through the receiver which often has a capacitor in series and thus blocks DC charge equalization. This is, of course, not the only reason that a loop is quieter than a single-wire dipole but is simply one of the reasons. Incidentally, "Quietflex" antenna wire, with its 1000v insulation reduced the problem to an acceptable level in the Arizona desert. I still use that wire for my dipoles. -- 73, Cecil http://www.qsl.net/w5dxp |
Is It double bazooka less noisy?
For the past few days we had rain and lighting. Prior to any rain
hitting my antennas the steeady background noise hissing came up. The noise came up first on my high dipoles, two regular dipoles at 150-160 feet. One was bare #14 copperweld, the other is insulated #10. they were both equal as near as I could tell. It came up the same but later in time on my three low 80 meter dipole antennas at about the same rate. Two were bare wire and one was a coaxial double bazooka. All are at about 35-40 feet high. I have a 1/4 wl shorted stub I use as a second harmonic trap on 80 meters. It switches in and out with a relay on an RCS-8V switch that selects trunk lines to antennas. I pulled the relay wire off, and the 80 meter dipoles had then same steady noise as with the stub in. The dc path had no effect at all on steady noise, but on the high dipoles, both the insulated one and bare one, there was a popping noise about once every second or two that went away with the dipoles center conductor grounded. I could hear this popping noise on any antenna near the dipoles. I added a 470K resistor to the 80M feedlines and the popping noise quit. I removed it and added a choke and the popping noise quit. When lightning would hit the popping noise would quit for a while, and then come back. As the storm got worse the noise got worse. When the rain was very heavy and lightning very close, I stopped for a while. At that point the noise was terrible on all antennas, but definately worse in level on the high antennas. It was no better and no worse on any antenna at the same height. All through this my IAC double bazooka was no quieter than a regular dipole made from #16 bare copper located 100 feet away at the same height. This test was with all antennas in place at the same time on the same day in the same weather. 73 Tom |
Is It double bazooka less noisy?
wrote:
... but on the high dipoles, both the insulated one and bare one, there was a popping noise about once every second or two that went away with the dipoles center conductor grounded. All through this my IAC double bazooka was no quieter than a regular dipole made from #16 bare copper located 100 feet away at the same height. I forgot to ask. Did the double bazooka arc like the ungrounded dipoles? -- 73, Cecil http://www.qsl.net/w5dxp |
Is It double bazooka less noisy?
Cecil Moore wrote:
Precipitation static doesn't always occur during thunderstorms. It's effects are greatly reduced in high humidity environments. For precipitation static to occur requires charged particles. And you don't know if charged particles even existed during your experiment. To separate charged particle effects from lightning effects you need to run your experiment without the clouds and thunderstorms under conditions that guarantee charged particles. That would be during a dust storm on a clear sky day under low humidity conditions as often exist in Queen Creek, AZ. Cecil, This is close to being an all-time RRAA classic. Precipitation, at least in the form of rain, often occurs when the humidity is quite high. Do you suppose they should have named it dust storm static rather than precipitation static? Or perhaps dry rain static? 8-) 73, Gene W4SZ |
Is It double bazooka less noisy?
Gene Fuller wrote:
Precipitation, at least in the form of rain, often occurs when the humidity is quite high. Yes, and triboelectric charging is known to be magnitudes worse in low humidity conditions. On this web page: http://www.esda.org/basics/part1.cfm it says that a worker at a bench can expect 6000v when the relative humidity is 10-25% Vs 100v when the relative humidity is 65-90%. Do you suppose they should have named it dust storm static rather than precipitation static? Or perhaps dry rain static? "Charged particle" static would have been more descriptive since "precipitation" is most associated with falling H2O. If the relative humidity is 10% when the rain starts falling, seems the precipitation static would be worse than if the relative humidity was 90% when the rain started falling. Dry snow falling in low relative humidity conditions could certainly carry large charges. Dry wind driven dust particles in low relative humidity conditions are often associated with precipitation static. But assuming that raindrops falling in high humidity conditions are electrically charged is a questionable assumption. And trying to detect precipitation static noise in the presence of lightning seems like looking for a needle in a haystack. It is good engineering practice to try to isolate what one is trying to measure. The best way I know of to isolate precipitation static from other noise sources is to perform the measurements under clear sky, windy, low humidity conditions in the desert. I strongly suspect that w8ji didn't detect any of the arcing noise in the double bazooka that he detected in the bare wire ungrounded dipoles. Was that a noise reduction? -- 73, Cecil http://www.qsl.net/w5dxp |
Is It double bazooka less noisy?
This is hilarious.
No matter in what context, it appears bazookas cause long threads. 73 H., NQ5H |
Is It double bazooka less noisy?
H. Adam Stevens, NQ5H wrote:
This is hilarious. No matter in what context, it appears bazookas cause long threads. I don't remember the bazooka ever being discussed before in the context of precipitation static so it is essentially a brand new topic. -- 73, Cecil http://www.qsl.net/w5dxp |
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