|
You're no good on this subject without facts. Here are the most important ones:
All spark, whether macroscopic or microscopic, is oscillatory. This was proven in the mid 1800's. Hertz, proving the work of Faraday and Maxwell, used spark with a loop to show resonance. He drew the first passband graph. Thanks to Marconi, the most notable of early amateurs, spark radio was made practical.
If you touch a conductor to an active chassis you will probably hear the microscopic spark in your radio. Your probe and the chassis comprise the simplest form of antenna. The frequency is determined, by the resonance of that circuit.
A very good friend of mine frequently demonstrates spark radio. I have reminded him that he is in a strong RF field. He always counters that he doesn't use an antenna. And I always remind him that the circuit is now putting out microwaves. This was worth mentioning, not to embarrass my friend, but to open his eyes to the electro-magnetic wave. As a motion picture machine operator, I struck an arc light many thousands of times. In retrospect, I wonder how much VHF and UHF radiation was present. One theatre shielded it's lines. Another did not.
The garbonzo of all spark is lightning. It too has a resonant frequency determined by the length of spark, the pockets of charge and perhaps many other things worth contemplating. The electro-magnetic radiation from a lightning bolt may exceed it's energy in light or heat. And it's frequency is generally considered to be low, well below one megazhertz.
An energy analysis of a cloud-to-cloud bolt (more frequent than we used to believe in the latitudes of the U.S. and Europe), might release 85% of it's radio energy around fifty kilohertz. Another ten percent might be below 500 kilohertz. The rest distributes over a broad band of harmonics usually not higher than television channel two, 54 megahertz. If you see the radio signature of lightning above that than you are likely in the presence of very small and energetic discharges. These could be mirror-arcs in the tv antenna.
Who hasn't wondered how to harness lightning? We'll leave that subject to another discussion but please understand that gathering the low frequencies of lightning could begin with an antenna. And since amateurs love antennas, they can easily calculate that at 50 kilohertz one would need at least 9,600 feet or nearly two miles of wire. That would be the minimum. The larger the better.
Isn't the power grid big enough?
If this is the first time you've seen this relationship, then you have only now glimpsed the 'mother' of all surges: The so-called resonant surge.
Our unprotected electrical systems are just 'dummy loads' in the most massive antenna system around. And we haven't even talked about the direct hit.
|
 |
|
| |
|
Column two
Consider this: How much energy would you have to input into an 80 meter ham antenna in order to induce sparks into a coat hanger or a straight pin miles away? It's not a calculation I relish. Yet that is precisely what lightning does. Its low frequency induces high voltages into even uhf ham antennas. The resulting sparks in the system can re-resonate at the frequencies of the system. And even an ideal band-pass filter can't keep them out of the radio.
Arcing was no problem with our tube equipment. The first 'lightning arrestor' I saw was that little round bakelite device that clamped tv twin lead. A solid wire was connected from there to ground. At thirteen years of age, I couldn't grasp how this thing could arrest lightning. It was a kind of spark gap. It relieved lightning-induced currents. Tube TV's were practically impervious to lightning-induced currents. Especially when the energy was clamped through a spark gap. But ol' timers were woefully deficient in the understanding of that spark when making the transition to modern solid state radios. And that's why you hear this dubious advice: Tell ya whatcha do. You unplug!
If anyone of the old timers had taken the discharges seriously, we might not be calling that famous filter a 'low pass' filter. It would be a broad band pass filter: TVI/lightning block. Remember the low frequencies? They sail through a low pass filter.
Even today's modern books miss this point completely. Otherwise, those nifty little filter diagrams that attenuate harmonics on modern transistor amplifiers would have a low frequency cuttoff.
Now why would you need all that since you leave your station unplugged when not in use? Because the things we're talking about do not occur during lightning storms alone. I have logged at least a dozen 'out of the blue' events at my station. I was often receiving or transmitting when they occured. I have been in a unique position to spend a lot of time around the equipment. One chapter in my notebook is called : 'Clicks, Clacks and Cracks.' I might add: 'Bangs.' Those are the sounds of discharges in the equipment. To keep bangs down to clicks, serious surge suppression is called for.
If you have read this far, then you can see you are vulnerabale to three antennas: The power line, the phone line and your ham antenna. And there's good, better and best in any products or methods of surge suppression.
The best thing to do with the house wiring is a serious subject here. Perhaps you'd like to correspond about it. But the best available point-of-use consumer method is offered by 'Brickwall'. You can click on the link to study this 110 volt filter-type surge device. Any surge strip will shunt spikes. The ones with RFI filters are even more useful though most cuttoff above one megahertz. The 'brickwall' seems to live up to its name, at least until we discuss grounding.
"The Brickwall" surge suppressor |
|
|
|
