| Home |
| Search |
| Today's Posts |
|
#8
|
|||
|
|||
|
Cecil Moore wrote: 1. A highly charged particle encountering one element of a bare copper wire dipole will transfer approximately half its charge to the wire. 2. A charge unbalance between the two elements of a dipole will cause a differential current to flow in a link coupled system. 3. The differential current may be detected by an RF receiver. Only when it is AT THE FREQUENCY the receiver is tuned to. So when you provide a DC path that does not short the antenna at radio frequencies, it does nothing. The only exception to this is if the charge actually causes something to arc, but even then it is a long term buildup of charge. This is simply a false statement. You can a call me a liar if you like, but it doesn't change the facts. All that crud hitting the antenna isn't significantly different in potential than the air around the element, it just has a lower impedance. Absolutely false! Charged dust particles are a fact of life in the Arizona desert. There is often not enough moisture in the air to discharge them. Your limited experience is showing. How often does the relative humidity get down to 10% with high winds and dust in Georgia? I haven't lived in Georgia all my life. Most of my experience with this is actually in Ohio, but on other reflectors like TowerTalk everyone seems to share the same common experiences. As a matter of fact, it is rather silly to claim the particles discharging make noise and then at the same time claim that a DC path somehow reduces or eliminates that noise. I didn't claim it "reduces or eliminates that noise". I claimed it eliminates arcing which is certainly a type of noise. We agree there. So why are you arguing? If it charges the antenna to the point where a dielectric fails the sudden change will make a terrible noise and may even cause damage. This is why no one should have a large element high in the air that does not have a leakage path. The CLOSER the antenna would be allowed to float to the potential of the particles the LESS change in potential would occur. Pulling the element to earth would make each tiny discharge worse and make more noise, not less. My problem was that 1/2 of the antenna was at DC ground potential and the other half was floating which is typical of a store-bought G5RV. That seems to cause the worst case of arcing. But it is simple physics to realize that each particle acts independently. The charge transfer from each particle causes a tiny differential current between the two elements of the antenna. Millions of unsynchronized collisions per second certainly would produce differential RF noise. In that case a ground on the floating side would make no difference, or if anything make it worse. Think about it, or draw it on paper. The charge differential (as you say above) is between the floating particles and the earth. The greater the charge difference, the larger the amount of charge transferred (as you said above). If we agree on what you say above, the "millions of unsynchronized collisions" would not impart less charge to the antenna when it is closer to earth potential, they would impart more. The fact is a dc path doesn't change a thing with one single exception, the dc path prevents an antenna from building a charge in the capaciatnce of the system, and prevents that voltage from building to the point where some dielectric fails. Indeed that happens, and that is why large high antennas should have a leakage path to earth. Even on a clear calm day my 160 dipole at 300 feet, if I let the coax dangle a few feet above earth, will knock a person for a loop when touched. Inactive power lines, when open circuited, have to be clamped to ground for the same reason. On a windy day the recharge rate of the dipole is faster, and faster still in inclement weather. When the weather is bad, there is corona off the antenna that makes a sizzling sound that starts out as a series of slow pops and builds to the point where it almost turns musical or tonal. If lightning flashes even far in the distance, it immediately stops and rebuilds. The higher the antenna and the sharper and more extended the ends, the worse the problem is. Even when no moisture is hitting the wire. 73 Tom |
| Thread Tools | Search this Thread |
| Display Modes | |
|
|
Similar Threads
|
||||
| Thread | Forum | |||
| Transfer Impedance(LONG) | Shortwave | |||
| ECM Noise on CB | Equipment | |||
| 'Crackling' Noise on HF Band | Shortwave | |||
| RACAL RA-17C12 with DSP / digital readout | Shortwave | |||
| Automatic RF noise cancellation and audio noise measurement | Antenna | |||