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Noise level between two ant types
Ian White GM3SEK wrote: This makes the choices quite complex, and makes generalization impossible. Quote an example, and someone else will quote you a counter-example. Just one other thing: PLEASE let's not talk about elements being "grounded", way up there at the top of a tower. The entire topic and people's reactions about precepitation noise is fascinating. People actually seem to think the little particles voving through the air charge the antenna to a different potential than the air around the antenna, and that a "dc" path to earth or "dc" path around an element somehow magically stops RF noise. Certainly it is possible for a conductor very well insulated from earth to charge to the potential of the static field around the antenna, and flash over to "ground" through some path that breaks down. Of course only a fool would have equipment that allows that to happen while large antennas are being used or connected. This is an entirely different thing than the corona discharge that makes what people typically call "P-static". 73 Tom |
#3
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Noise level between two ant types
wrote:
People actually seem to think the little particles voving through the air charge the antenna to a different potential than the air around the antenna, and that a "dc" path to earth or "dc" path around an element somehow magically stops RF noise. Let's say we have the following bare-wire dipole system link coupled to the receiver (in fixed font). | | dipole element A link coupled | -////- +--------------------------------------------------///////--+ | +-----------------------------------------------------------+ | | dipole element B | Let's assume one highly charged particle hits dipole element A and transfers half of its charge. Element A will then have an excess charge one half of which will migrate through the link while equalizing the charge between element A and element B. That charge migration/equalization no doubt results in an RF noise pulse. This experiment can easily be performed by anyone. Rub one's leather soles on a wool carpet, touch one side of the dipole, and listen for noise in the receiver. Guaranteed, it will be there. Now multiply the above by millions of charged particles randomly encountering the bare-wire dipole. The charge on each side of the dipole will never be exactly equal. Thus, continuous broad-band noise will be continuously transferred through the link as long as the particles are transferring charge to the antenna. That's what some hams are hearing during dry-air dust and snow conditions. Some have even reported being able to hear individual particle collisions from large snowflakes. -- 73, Cecil http://www.qsl.net/w5dxp |
#4
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Noise level between two ant types
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