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## Re: [TowerTalk] CATV & Phone grounds

 To: "Tower Talk List" Re: [TowerTalk] CATV & Phone grounds "Jim Brown" Tue, 11 Jul 2006 22:47:58 -0700
 On Tue, 11 Jul 2006 12:13:49 -0700, Bill Turner wrote: >As I understand it, lightning >really does flow in one direction, making it DC but having a >square-wave nature. Is that where the HF component comes from? >Lightning doesn't really change directions, does it? First, think of the current flow in the output stage of any electronic amplifier. The instantaneous current flow has a DC bias -- that is, it is always flowing in the same direction -- but it has strong RF components, namely the signals they are amplifying. The initial charge that sets off the lightning strike is the DC bias, but the fact that it comes in the form of a fast risetime pulse can cause oscillation in the resonant circuit that is the discharge path. As others have noted, the HF components comes from the very fast rise time of the current discharge. Remember that from the mathematical analysis that Fourier taught us more than a century ago, any transient or non-sinusoidal waveform will resolve into an infinite number of sine waves of increasing frequency (or if it is an impulse, a series of sine waves of decaying strength). If the single is repetitive, the higher frequency components will be harmonically related to the repetition rate. The resulting waveform can still come out with a DC bias, and the waveforms don't necessarily all need to begin at the same instant (thus they can resolve into any DC value, based on the physics of what else is happening in the circuit). Hope this helps. Jim Brown K9YC _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk
 Current Thread Re: [TowerTalk] CATV & Phone grounds, (continued) Re: [TowerTalk] CATV & Phone grounds, Bill Turner Re: [TowerTalk] CATV & Phone grounds, Keith Dutson Re: [TowerTalk] CATV & Phone grounds, Bill Turner Re: [TowerTalk] CATV & Phone grounds, K8RI on Tower talk Re: [TowerTalk] CATV & Phone grounds, Keith Dutson Re: [TowerTalk] CATV & Phone grounds, Jim Lux Re: [TowerTalk] CATV & Phone grounds, Gary Schafer Re: [TowerTalk] CATV & Phone grounds, K8RI on Tower talk Re: [TowerTalk] CATV & Phone grounds, Gary Schafer Re: [TowerTalk] CATV & Phone grounds, Jim Lux Re: [TowerTalk] CATV & Phone grounds, Jim Brown <= Re: [TowerTalk] CATV & Phone grounds, JC Smith Re: [TowerTalk] CATV & Phone grounds, K8RI on Tower talk Re: [TowerTalk] CATV & Phone grounds, Gary Schafer Re: [TowerTalk] CATV & Phone grounds, Red Re: [TowerTalk] CATV & Phone grounds, K8RI on Tower talk