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Noise level between two ant types
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Noise level between two ant types
Cecil Moore wrote: When I lived in the Arizona, clear-sky wind-driven charged dust particles transferred lots of energy to my bare-wire G5RV. It caused arcing whether the outside braid was grounded or not. It only happened when the wind was blowing and the humidity was very low. But that effect is common no matter where we live. As I've said several times, a high dipole here for 160m charges enough to knock you on your rear on a calm sunny day if the coacial line is well insulated from ground. It is not wise tol have a large high antenna that was well-insulated from ground, since the accumulated charge can suddenly discharge through a series capacitor and damage equipment. Utility companies must ground unused wires that run for miles to prevent build up of charge, so that is not something that just occurs in arid climates. Do you agree that a charged particle will transfer energy to the bare wire in a dipole when it touches it? If not, why not? Of course it will IF it is at a different potential than the wire. If the antenna were link coupled, do you agree that the above transferred energy will try to equalize between the two dipole elements? If not, why not? Of course it will. Do you agree that the equalizing of the charges between elements would cause a current to flow through the link? If not, why not? Of course it will. I disagree wth your contention that the link, if the noise comes from each particle hitting the antenna, will reduce noise. That's the part that makes no sense. Maybe you can explain why the link (or folded element) would reduce that noise. 73 Tom |
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Noise level between two ant types
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Noise level between two ant types
Bob Miller wrote: I have a low, 30 feet or so, 80 meter dipole fed with ladderline, through an mfj 989c tuner. Hot humid clime (Texas). Is the ground wire on the back of the tuner, going to a ground rod, enough to bleed off electrical build up? Almost anything is enough to do that. The charge rate is extremely low. My 318 foot tall insulated tower had a measured charge rate in the ten's of milliamperes as measured during approaching thunderstorms. Of course taking care of a lightning bolt or EMP from a lightning strike someplace around the area is another story. 73 Tom |
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Noise level between two ant types
Bob Miller wrote:
I have a low, 30 feet or so, 80 meter dipole fed with ladderline, through an mfj 989c tuner. Hot humid clime (Texas). Is the ground wire on the back of the tuner, going to a ground rod, enough to bleed off electrical build up? If there is a DC path to ground from *BOTH* sides of the dipole, the answer is yes. But, looking at the 989c schematic, I don't see a DC path to ground from one of the balanced line outputs. -- 73, Cecil http://www.qsl.net/w5dxp |
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Noise level between two ant types
Cecil Moore wrote:
Bob Miller wrote: I have a low, 30 feet or so, 80 meter dipole fed with ladderline, through an mfj 989c tuner. Hot humid clime (Texas). Is the ground wire on the back of the tuner, going to a ground rod, enough to bleed off electrical build up? If there is a DC path to ground from *BOTH* sides of the dipole, the answer is yes. But, looking at the 989c schematic, I don't see a DC path to ground from one of the balanced line outputs. I forgot to say that your high humidity probably provides a path to ground from the other tuner terminal. It was only during super low humidity conditions in the Arizona desert that I experienced the arcing process during high winds. -- 73, Cecil http://www.qsl.net/w5dxp |
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Noise level between two ant types
On Tue, 13 Jun 2006 15:43:29 GMT, Cecil Moore
wrote: Cecil Moore wrote: Bob Miller wrote: I have a low, 30 feet or so, 80 meter dipole fed with ladderline, through an mfj 989c tuner. Hot humid clime (Texas). Is the ground wire on the back of the tuner, going to a ground rod, enough to bleed off electrical build up? If there is a DC path to ground from *BOTH* sides of the dipole, the answer is yes. But, looking at the 989c schematic, I don't see a DC path to ground from one of the balanced line outputs. I forgot to say that your high humidity probably provides a path to ground from the other tuner terminal. It was only during super low humidity conditions in the Arizona desert that I experienced the arcing process during high winds. I can't recall seeing any gap-sparking here in the San Antonio area. When it's hot, it's usually pretty humid, too. bob k5qwg |
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Noise level between two ant types
Bob Miller wrote:
I can't recall seeing any gap-sparking here in the San Antonio area. When it's hot, it's usually pretty humid, too. If you have an o'scope, please hang it across the transmission line wires during your next dust storm and report the results compared to a calm day. -- 73, Cecil http://www.qsl.net/w5dxp |
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Noise level between two ant types
wrote:
Cecil Moore wrote: When I lived in the Arizona, clear-sky wind-driven charged dust particles transferred lots of energy to my bare-wire G5RV. It caused arcing whether the outside braid was grounded or not. It only happened when the wind was blowing and the humidity was very low. But that effect is common no matter where we live. As I've said several times, a high dipole here for 160m charges enough to knock you on your rear on a calm sunny day if the coaxial line is well insulated from ground. During the "H Field Antennas" thread, you said the following: ************************************************** ************* Reg Edwards wrote: Precipitation static, eg., from highly charged raindrops and fine snow or fine sand, impinging on the antenna wire, just causes an increase in receiver white noise level. It can be reduced but not removed by using a very thickly insulated antenna wire, like the inner conductor of a coaxial cable complete with its polyethylene jacket. ---- Reg. W8JI replied: I've never seen a case of precitation static occuring that way. In every single case I've seen, whether on tall buildings, tall towers, or antenna hear earth, it has always been corona discharges from the antenna or objects near the antenna. ... 73 Tom ************************************************** ************** I have only noticed the charged particle arcing in Arizona when the wind was blowing and that is what I am reporting. It is not wise to have a large high antenna that was well-insulated from ground, since the accumulated charge can suddenly discharge through a series capacitor and damage equipment. Where does the accumulated charge come from if not from charged particles? If the antenna is link coupled, the charge equalizes between the two dipole elements and, in my experience, doesn't arc. Do you agree that a charged particle will transfer energy to the bare wire in a dipole when it touches it? If not, why not? Of course it will IF it is at a different potential than the wire. If the antenna were link coupled, do you agree that the above transferred energy will try to equalize between the two dipole elements? If not, why not? Of course it will. Do you agree that the equalizing of the charges between elements would cause a current to flow through the link? If not, why not? Of course it will. Seems we are in agreement that charged particle RF noise can therefore be picked up by a receiver as Reg says above. It is only logical that it will be worse when the wind blows causing more charged particles to encounter the antenna wire. And, as shown below, it is only logical that a folded dipole would transfer less of that noise to the link than a non-folded dipole. I disagree with your contention that the link, if the noise comes from each particle hitting the antenna, will reduce noise. That's the part that makes no sense. In my experience, it eliminated the arcing. Thus it eliminated the *AURAL* arcing noise that my ears were hearing. Why does that make no sense? I was very clear that my receiver was off and disconnected at the time and that I made no RF noise measurements. A short, or 4:1 voltage balun, or choke, or link across the connector eliminated the *AURAL* arcing noise. Maybe you can explain why the link (or folded element) would reduce that noise. Seems you confused my statements about aural noise with RF noise. I have previously said I didn't measure the RF noise. In any case, please see the pictures below to understand why a folded element redirects the charge equalization process away from the link. The process of equalizing the charge on the non-folded dipole elements causes RF noise across the link which is picked up by the S-meter on the receiver. I observed that many times in AZ and wish I had made some measurements. The S-meter reports a higher level of charged particle noise during high wind conditions and dry-air snowstorms. Please explain what it is about the following that you don't understand. 1. The equalizing of the element charges on a link coupled dipole will cause a current to flow through the link resulting in higher RF noise readings on the S-meter during high wind conditions when more charged particles are encountering the antenna wire. 2. Turning the dipole into a folded dipole (or loop) gives a preferred localized path for the equalization of the charge. Not nearly as much RF noise current flows through the remote link. Maybe a picture would help. Here's a non-folded dipole with a charge hitting it. In order to equalize charge with the other element, part of the charge must flow down the transmission line, through the link, and back up the transmission line to the other dipole element. Virtually all of the pulsed charge equalization process goes through the link. ---------CH----+ +--------------- | | / / | | link ************************************************** ************** +--------------------------------+ +--------CH----+ +---------------+ | | / / | | link Here's a folded dipole with a charge hitting it in the same relative place. What is the most efficient preferred path for equalizing the charge with the other element? Not down the transmission line and through the link but simply straight through the antenna wire. Hint: Charge would rather take the 50 foot path of least resistance than a 200 foot path of most resistance. Eureka! The folded dipole is less noisy during high wind conditions than is the non-folded dipole because most of the charge equalization takes place locally through the antenna wire and not remotely through the link. BTW, thanks for forcing me to think this through in detail. -- 73, Cecil http://www.qsl.net/w5dxp |
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