Thanks BJ, DISHDIIGER. I can't believe how my idea to get some extra station has turned so complicated! I digest, a few questions please guys, what do mean by shield side? Would I attach to the shield side just before entering the house? Where would I ground this, would I have to run a cable all the way to the main service point (fuse box?), which is on the other side of the house, about 50'? When you say grounding the receiver, I have have a seperate tuner, amp, pre-amp, turntable, & CD, do I ground them all together then to where, will the ground at the electrical outlet suffice?
Looks like I did another bone headed thing by using the metal pole! It is located 10' from the house, attach to the porch post, it 3' off the ground, should I replace it with wood and just ground the cable? What are spark gaps?
Thanks guys, I know I am truly lost and in need of much knowledge, please save the day and protect me from mother nature as I live in the lightning capital of the country (2nd only to someplace in Australia)! Thanks again....
MAC
Re "the shield side", you were talking about coax and twinlead. The coax is an unbalanced feedline, ie it has a center conductor carrying the signal, and the outside shield, which is the ground. Usually you can buy a little grounding block that the coax from the antenna screws onto, and another coax to the receiver, and from this grounding block, you run a heavy wire to the house ground, usually a cold water pipe near your fuse box. This grounds the outside shield wire of the coax.
The twin-lead is a balanced feed, ie there is no shield to ground, and if you do ground one of the wires, it will usually destroy the effectiveness of the antenna. This is where the spark gap comes in. I think Radio Shack used to sell spark gaps, but I doubt that they do anymore, you might try a ham radio store if there is one near you. If you go to a library, and find a copy of the ARRL Antenna Book, and look up lightning protection, you can find some suggestions on how to make one. Basically just a terminal where the twin-lead from the antenna connects to twinlead to the receiver, and each wire is connected to another connector which is very close to, but not connected to a well grounded block. So that if you get a lightning strike, it will jump across the gap and go to ground, rather than to your equipment. Probably won't save your equipment, but might save you from a fire. I think if it was me, I would use a BALUN (Balanced to UNbalanced) converter, which is nothing but a little transformer. Ie the twinlead goes to a coil that is coupled, but not electrically connected to another coil that's connected to the leads of a coax. If you've used an OLD TV, you're probably familiar with these, as a little device that converts coax to twinlead, or visa-versa. The advantage of a BALUN is that they typically don't have a DC connection between the twinlead and the coax, although it's possible that it might. So if you use a BALUN, and ground the coax, it will probably protect you pretty well.
By the grounded receiver thing, I was just referring to the fact that most receivers are grounded through it's power plug, if it is either a 3-prong plug or a 2 prong plug with one prong wider. This will generally ground the case of your equipment, and the shield of your coax to your house ground. Not quite as good as grounding at the service entrance, but usually OK.
Your comment about the service ground being on the other side of your house, is typical. It's almost never convenient to ground things like this according to code, which is why most people don't follow code. I don't even come close, for the same reasons, however I don't live in a frequent lightning area, although I used to.
My feeling is that if I were in your situation, I wouldn't worry that much about an antenna that's only 10' from the house, particularly if you're using insulated wire that isn't connected to the pipe, and using a balun on the twinlead. If you get a lightning strike that close to your house, protecting your receiver will be the least of your worries.
Relative to the various things people do to protect themselves from lightning, some are aimed at protecting your house from a fire or something major in the event of an actual lightning strike Other measures are aimed at protecting you from the static potential that preceeds a lightning strike. Still other measures are aimed at preventing the lightning strike in the first place.
I'm convinced that a large percentage of damage that people attribute to lightning strikes is really caused by the static potential that occurs right before a lightning strike, and that the actual strike isn't what causes the damage. But the static potential can be very damaging to electronics, so it's probably not important to the victims that it wasn't the strike that killed their equipment. Another high percentage of the damage is caused by strikes to telephone lines and power lines, such that the surge comes in through these wires, rather than through your antenna wires. I think it's very rare that an actual lightning stike comes in though your antenna wire.
One of the most misunderstood features of grounding antenna structures such as a tower or something, is that people think that by grounding an antenna tower or pole, you are making it more likely that that tower will be struck by lightning by giving the lightning a path to ground. In actuality, you are making it LESS likely that the tower will be struck, because grounding the tower will give the static potential a path to ground. When a storm cloud approaches, the clouds will develop a high voltage, either positive or negative, and the largely non-conductive and poorly grounded surface of the soil, trees, and buildings under the cloud will develop an opposite potential, much like a big capacitor. Ie if true ground deep under the surface is zero volts, and the clouds are say a positive thousands of volts, the surface objects will have an "INDUCED" static voltage that can be thousands of volts opposite to the voltage in the clouds, ie negative if the clouds are positive, and positive if the clouds are negative. This makes the actual voltage differential twice the actual voltage in the clouds. By grounding an antenna tower or house or barn with lightning rods, etc, you are basically dissipating that induced static charge, putting your tower at ZERO volts rather than a high induced static voltage. This actually protects your house, not by giving the lightning a path to follow, but actually prevents your house or tower from being struck in the first place. Lightning will strike when the voltage differential between the clouds and the object gets up to a high enough value. If the clouds are say a positive thousand volts (it's much higher, but that's just an illustration), and your house is ZERO volts, and some tree hundreds of yards away is a negative thousands volts (again an illustration), the lightning is going to hit the tree, because the voltage differential between the ungrounded tree and the cloud will be 2000V divided by the distance to the cloud, compared to 1000V divided by the distance to the cloud, so the strike will hit the ungrounded tree, rather than the ungrounded house. Of course if you have a very high tower, that increases the chance of a strike by reducing the distance to the cloud, and tall towers suffer a lot of strikes, but grounding them actually decreases the odds of a strike, rather than increasing the odds.
Anyway, the point of the above is that grounding a house with lightning rods, or grounding a tower, is most effective by it's dissipating the induced static charge that preceeds a lightning strike, making a strike less likely, however I would not connect my receivers and other electronics to the tower ground unless that tower ground is bonded to the service ground. I believe they are best protected by their own house ground of the electronics being plugged into a grounded outlet. I really believe that you're better off not grounding your antenna at all if your tower or pipe isn't bonded to the service ground because if the antenna is grounded to a ground not bonded to the house ground, then you're likely to get high voltage differences between the two grounds. The second ground can still protect you by reducing the induced potential that your antenna will experience, even though you're not connected to it.
Just my opinion though, based on the assumption that most people are not going to follow NEC code to the letter, and just trying to suggest what I think is the safest way to deviate from the code.
Thanks in advance for any input, greatly appreciated
!
. I hope you got something out of this, I did, quite an interesting discussion.
