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Scanner / Receiver Antennas For discussion of any type of receiving antenna used by a scanner or receiver base, mobile or handheld.

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Old 04-09-2011, 7:21 PM
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Exclamation Grounding SWL Antenna?

I am going to install my W8AMZ 160m 1/2 sloper on the roof of my apartment. I am going to string it between two waste vent pipes, the sloper has a ground wire to be attached to a ground but the location of the vent pipes there is no where to ground it. I could run a wire from my ground rod to the antenna but that would be about a 50 foot run, I know thats not good because the ground it self could start acting as a antenna. SO what should I do to ground it? Should I leave the ground wire unattached or go ahead and run a 50 foot wire to ground? The only thing that is metal on the roof is dryer exhaust vents but I do not believe those are grounded. Thanks in advanced!
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Old 04-09-2011, 7:27 PM
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I thought I would post a picture of the antenna so it would give you all a idea of what I am working with.
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Old 04-09-2011, 8:17 PM
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While it's possible this would work as a SWL antenna, I kinda have my doubts. This antenna is designed as an electrically shortened antenna for 160m (between 1.8 and 2.0 mhz). As it's designed for transmitting, I suspect there's a matching network in that long black pipe. The further away you get from the designed frequency range, the more loss you are likely to incur. By the way, for others who might be curious, here's the website;

Products

As to grounding - I agree that the vents would likely not work well. It might work OK without a ground - but a better solution would probably be to keep the business end close to the ground, and connect it to a ground rod (which really isn't a particularly effective RF ground, but that's a whole 'nother story), or connect it to a cold water pipe, then connect the wire at a fairly sharp angle to a fixed point.

That's assuming your apartment manager gave you the OK to do this in the first place - kudos to him/her if s/he did!

best regards..Mike
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Last edited by ka3jjz; 04-09-2011 at 8:23 PM..
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Old 04-09-2011, 8:38 PM
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BT-word for word my dilemma as you well know-I originally had mine grounded to a fire escape, which is bolted to the I-beam frame of this building..but was advised against it in here due to potential redirecting of lightning to humans. So I now have mine grounded at the coax entry point inside my apt, at the antenna switch with an arc pill in it, #6 ground wire from switch to cold water pipe in bathroom. This is all I have for a ground. Hopefully my setup may help you there. If you have a bathroom near your station I suggest running something similar.
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Old 04-09-2011, 10:03 PM
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Quote:
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BT-word for word my dilemma as you well know-I originally had mine grounded to a fire escape, which is bolted to the I-beam frame of this building..but was advised against it in here due to potential redirecting of lightning to humans. So I now have mine grounded at the coax entry point inside my apt, at the antenna switch with an arc pill in it, #6 ground wire from switch to cold water pipe in bathroom. This is all I have for a ground. Hopefully my setup may help you there. If you have a bathroom near your station I suggest running something similar.
I question the decision to change the ground from a fire escape to a cold water pipe. What would happen if lightning did strike? With the fireplace ground, it would endanger the very few folks on the fire escape, but with the water pipe ground you could easily shock (or worse) folks washing their hands or the dishes, using the toilet, or even kids taking a bath. Not something I would really want to do.

Grounding to the building's steel frame is quite common for roof mounted towers. Quite often this is the route that the building's lightning rods also use as their path to the earth as well. These grounds are directly to the I-beams though and not indirectly through something like a fire escape though. When a roof mounted tower is planed, they make certain that the beams are not only physically connected together, but also electrically connected to reduce any impact of rust or other corrosion causing a high resistance path. Apartments may not do this since they rarely go over just a few stories.
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Old 04-09-2011, 10:52 PM
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I question the decision to change the ground from a fire escape to a cold water pipe. What would happen if lightning did strike? With the fireplace ground, it would endanger the very few folks on the fire escape, but with the water pipe ground you could easily shock (or worse) folks washing their hands or the dishes, using the toilet, or even kids taking a bath. Not something I would really want to do.

Grounding to the building's steel frame is quite common for roof mounted towers. Quite often this is the route that the building's lightning rods also use as their path to the earth as well. These grounds are directly to the I-beams though and not indirectly through something like a fire escape though. When a roof mounted tower is planed, they make certain that the beams are not only physically connected together, but also electrically connected to reduce any impact of rust or other corrosion causing a high resistance path. Apartments may not do this since they rarely go over just a few stories.
I feel the same way but I got all worried when this guy brought the possibility to me I still have the #6 ground run setting on the roof up there and could reconnect in a heartbeat. I think I may do that it was a solid ground situation, and if I had to quickly disconnect it in a bad storm all I need to do is slide the livingroom glass door open and the ladder to the roof is right there-just 8 steps and SNIP!
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Old 04-10-2011, 1:16 AM
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Well I went ahead and installed the antenna tonight, trying to hide from everyone eben tho I have had the maintenance man tell me I can get on the roof. Heck he even helped me one time with putting a antenna up on the roof. Well anyways I am listening to CHU on 3.330 and getting a 7s to 9s on my Icom R75. I head Andrews giving a EAM on 11.175 and was getting a 3s with very little RF noise. I also was hearing New York Volmet on 6.604 at 20s on the meter! So I hope this is working good. Not sure what I should be able to hear.... I will take pics of the install and post tomorrow when the sun is up..
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Old 04-10-2011, 6:42 AM
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Sounds like it's working well in spite of the tuning network. Now the fun begins - deciding what you want to hear...best regards..Mike
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Old 04-10-2011, 9:25 AM
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Yeah I agree-those few copies sound good to me-waiting for your next report
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Old 04-10-2011, 8:14 PM
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Well here are some pictures of my antenna setup during the day. I will take some tonight if the storms don't come in to early..
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Old 04-10-2011, 8:59 PM
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Hows she running BT? looks real good up there! You going to settle in and log some DX?
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Old 04-10-2011, 9:03 PM
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Paint the vent pipe extensions and antenna feed point light gray and they will be less noticeable.
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Old 04-22-2011, 2:53 PM
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Proper ground is VERY important on any longwire, any band. End feed longwire designs use the ground wire as a ground plane. Leave that out, and you're trying to work with half an antenna. In this case, coupling is more than likely a good thing. If you still have SWR issues that can't be tuned out, I'd suspect something else is giving you problems.

One real issue is static buildup. Snow, rain, ice, even wind can cause static. Doesn't sound like much, but we're talking some real transient voltage that can fry anything it's attached to. I personally wouldn't run one without adding a transient trap (gas cap) to the feed line, preferably outside where the pop and crackle won't give the cat a heart attack. Anything goes ZAP! and it blows the cap instead of the radio. Of course, that leaves you with yet another ground to deal with. Is it fun yet?

If it's not too late, you might want to try trading yours in on a true dipole. There at least you don't have the ground plane issue.
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