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#1
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Loop antenna question
I just got through picking up a ton of discontinued wire from my local Home
Depot, and was planning on building a "broomstick" antenna like some I found described on the net. Got a question though: doesn't "stretching out" the coil to a meter or more reduce the inductance of the resulting coil? Why wouldn't it work better to just leave it on the spool? I was under the impression that the formula for calculating the inductance for a given coil involved multiplying the square of the number of coils by the ratio of the coil width to length. Wouldn't this mean that a "longer" coil would have a lower inductance than a "shorter" coil, given the same length of wire and approximate diameter of coils? Forgive me if I'm being stupid here, it has been twenty years since I have attempted anything like this, but that was what I thought. The main account I am thinking of was related by someone in Saudi Arabia who wrapped 1.2 kM of wire around a piece of PVC and vastly improved their reception of WWV in the states. I was going to do something similar, and then looked at the two spools of wire that I was about to unwrap. They are already coils, so shouldn't I be able to just hook them up to an aligator clip and stick this to my whip antenna? (I am now thinking about taking the wire off of the smaller spool and adding it to the larger. Shouldn't that work?) And if I leave the wire on the spools (which are plastic) couldn't I turn them toward or away from the station of interest to further improve reception? (I could even put this in my attic, gaining a few feet of elevation and hiding it from my unappreciative wife.) Any input on any part of this idea is more than welcome. I would greaty value the opinions of those who have actually done something like one of these two options. Thanks, Dave |
#2
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"Dave" wrote in message ... I just got through picking up a ton of discontinued wire from my local Home Depot, and was planning on building a "broomstick" antenna like some I found described on the net. Got a question though: doesn't "stretching out" the coil to a meter or more reduce the inductance of the resulting coil? Why wouldn't it work better to just leave it on the spool? I was under the impression that the formula for calculating the inductance for a given coil involved multiplying the square of the number of coils by the ratio of the coil width to length. Wouldn't this mean that a "longer" coil would have a lower inductance than a "shorter" coil, given the same length of wire and approximate diameter of coils? Forgive me if I'm being stupid here, it has been twenty years since I have attempted anything like this, but that was what I thought. The main account I am thinking of was related by someone in Saudi Arabia who wrapped 1.2 kM of wire around a piece of PVC and vastly improved their reception of WWV in the states. I was going to do something similar, and then looked at the two spools of wire that I was about to unwrap. They are already coils, so shouldn't I be able to just hook them up to an aligator clip and stick this to my whip antenna? (I am now thinking about taking the wire off of the smaller spool and adding it to the larger. Shouldn't that work?) And if I leave the wire on the spools (which are plastic) couldn't I turn them toward or away from the station of interest to further improve reception? (I could even put this in my attic, gaining a few feet of elevation and hiding it from my unappreciative wife.) Any input on any part of this idea is more than welcome. I would greaty value the opinions of those who have actually done something like one of these two options. Inductance isn't all there is to an antenna.. you need capture area, too. Broomstick antennas are not all that good, and are not very efficient. Yes, they look good on paper, as the 'electrical length' is much longer than that much straight wire, but without capture area, the efficeincy drops way off. You're better with a longwire, even just a few meters (yards) run along the eaves of your house. |
#3
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I won't go into detail but the broomstick (or any helicaly wound antenna)
gives up performance for size. The straiter the wire, the better off you are. If you have the space, just stretch it out strait. "Dave" wrote in message ... I just got through picking up a ton of discontinued wire from my local Home Depot, and was planning on building a "broomstick" antenna like some I found described on the net. Got a question though: doesn't "stretching out" the coil to a meter or more reduce the inductance of the resulting coil? Why wouldn't it work better to just leave it on the spool? I was under the impression that the formula for calculating the inductance for a given coil involved multiplying the square of the number of coils by the ratio of the coil width to length. Wouldn't this mean that a "longer" coil would have a lower inductance than a "shorter" coil, given the same length of wire and approximate diameter of coils? Forgive me if I'm being stupid here, it has been twenty years since I have attempted anything like this, but that was what I thought. The main account I am thinking of was related by someone in Saudi Arabia who wrapped 1.2 kM of wire around a piece of PVC and vastly improved their reception of WWV in the states. I was going to do something similar, and then looked at the two spools of wire that I was about to unwrap. They are already coils, so shouldn't I be able to just hook them up to an aligator clip and stick this to my whip antenna? (I am now thinking about taking the wire off of the smaller spool and adding it to the larger. Shouldn't that work?) And if I leave the wire on the spools (which are plastic) couldn't I turn them toward or away from the station of interest to further improve reception? (I could even put this in my attic, gaining a few feet of elevation and hiding it from my unappreciative wife.) Any input on any part of this idea is more than welcome. I would greaty value the opinions of those who have actually done something like one of these two options. Thanks, Dave |
#4
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CW wrote: I won't go into detail but the broomstick (or any helicaly wound antenna) gives up performance for size. The straiter the wire, the better off you are. If you have the space, just stretch it out strait. Experimentation and experience have taught me that this is basically correct. "Broomstick" antennas give pretty good performance in a very compact space - they are even (marginally) "portable". But for signal-pulling ability, they'll never beat a well-thought-out longwire or randomwire. If you can tuck a one-meter broomstick into your car somewhere for traveling, you've got the world by the butt for shortwave listening away from home. But at home - your "permanent space" - go with a random or longwire, if you possibly can. Tony "Dave" wrote in message ... I just got through picking up a ton of discontinued wire from my local Home Depot, and was planning on building a "broomstick" antenna like some I found described on the net. Got a question though: doesn't "stretching out" the coil to a meter or more reduce the inductance of the resulting coil? Why wouldn't it work better to just leave it on the spool? I was under the impression that the formula for calculating the inductance for a given coil involved multiplying the square of the number of coils by the ratio of the coil width to length. Wouldn't this mean that a "longer" coil would have a lower inductance than a "shorter" coil, given the same length of wire and approximate diameter of coils? Forgive me if I'm being stupid here, it has been twenty years since I have attempted anything like this, but that was what I thought. The main account I am thinking of was related by someone in Saudi Arabia who wrapped 1.2 kM of wire around a piece of PVC and vastly improved their reception of WWV in the states. I was going to do something similar, and then looked at the two spools of wire that I was about to unwrap. They are already coils, so shouldn't I be able to just hook them up to an aligator clip and stick this to my whip antenna? (I am now thinking about taking the wire off of the smaller spool and adding it to the larger. Shouldn't that work?) And if I leave the wire on the spools (which are plastic) couldn't I turn them toward or away from the station of interest to further improve reception? (I could even put this in my attic, gaining a few feet of elevation and hiding it from my unappreciative wife.) Any input on any part of this idea is more than welcome. I would greaty value the opinions of those who have actually done something like one of these two options. Thanks, Dave ----== Posted via Newsfeed.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeed.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= 19 East/West-Coast Specialized Servers - Total Privacy via Encryption =--- |
#6
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The currrent in the wire produces an electromagnetic field which has a
defined radius. The field coil of a motor is used to turn it into a magnet so the motor will work...stretch out the windings, no emf imposed upon the core..no magnet-action-no work Stretch it out, you exceed the radius of the electromagnetic field, no interaction, no function. The whole purpose of the antenna in coil-structure is to use the induced emf to create a load on the antenna so it "thinks" it is longer Yodar "Dave" wrote in message ... I just got through picking up a ton of discontinued wire from my local Home Depot, and was planning on building a "broomstick" antenna like some I found described on the net. Got a question though: doesn't "stretching out" the coil to a meter or more reduce the inductance of the resulting coil? Why wouldn't it work better to just leave it on the spool? I was under the impression that the formula for calculating the inductance for a given coil involved multiplying the square of the number of coils by the ratio of the coil width to length. Wouldn't this mean that a "longer" coil would have a lower inductance than a "shorter" coil, given the same length of wire and approximate diameter of coils? Forgive me if I'm being stupid here, it has been twenty years since I have attempted anything like this, but that was what I thought. The main account I am thinking of was related by someone in Saudi Arabia who wrapped 1.2 kM of wire around a piece of PVC and vastly improved their reception of WWV in the states. I was going to do something similar, and then looked at the two spools of wire that I was about to unwrap. They are already coils, so shouldn't I be able to just hook them up to an aligator clip and stick this to my whip antenna? (I am now thinking about taking the wire off of the smaller spool and adding it to the larger. Shouldn't that work?) And if I leave the wire on the spools (which are plastic) couldn't I turn them toward or away from the station of interest to further improve reception? (I could even put this in my attic, gaining a few feet of elevation and hiding it from my unappreciative wife.) Any input on any part of this idea is more than welcome. I would greaty value the opinions of those who have actually done something like one of these two options. Thanks, Dave |
#7
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Brenda et al:
This statement facinates me: related by someone in Saudi Arabia who wrapped 1.2 kM of wire around a piece of PVC and vastly improved their reception of WWV in the states. 1.2 kM of wire; Heck of a lot of capture area ! Is there some ratio of loop diameter and spacing between the wire loops that results in the most capture area? There is a nice ratio of mirror diameter to magnification limits in telescopes This is the analogy I was thinking of. Dan Inductance isn't all there is to an antenna.. you need capture area, too. Broomstick antennas are not all that good, and are not very efficient. Yes, they look good on paper, as the 'electrical length' is much longer than that much straight wire, but without capture area, the efficeincy drops way off. You're better with a longwire, even just a few meters (yards) run along the eaves of your house. |
#8
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Tony Meloche wrote:
CW wrote: I won't go into detail but the broomstick (or any helicaly wound antenna) gives up performance for size. The straiter the wire, the better off you are. If you have the space, just stretch it out strait. snip If you can tuck a one-meter broomstick into your car somewhere for traveling, you've got the world by the butt for shortwave listening away from home. But at home - your "permanent space" - go with a random or longwire, if you possibly can. Tony For portable use, I've found the AT-271/A antenna designed for the PRC-25 or PRC-77 works quite well. It's about 10' long, and it's set up like the supports used for dome tents - to take it down - you pull the sections apart (they have a chain/shock cord running through them) and fold them for storage. I got it he http://www.american-milspec.com/c765.html Unfortunately, it's just a hair too long to fit inside the aluminum attaché case I transport my 7030 in. Personally, I think I'd use a slinky over a broom stick. More compact for travel, and if you have more room, you can spread it out. "Dave" wrote in message ... I just got through picking up a ton of discontinued wire from my local Home Depot, and was planning on building a "broomstick" antenna like some I found described on the net. Got a question though: doesn't "stretching out" the coil to a meter or more reduce the inductance of the resulting coil? Why wouldn't it work better to just leave it on the spool? I was under the impression that the formula for calculating the inductance for a given coil involved multiplying the square of the number of coils by the ratio of the coil width to length. Wouldn't this mean that a "longer" coil would have a lower inductance than a "shorter" coil, given the same length of wire and approximate diameter of coils? Forgive me if I'm being stupid here, it has been twenty years since I have attempted anything like this, but that was what I thought. The main account I am thinking of was related by someone in Saudi Arabia who wrapped 1.2 kM of wire around a piece of PVC and vastly improved their reception of WWV in the states. I was going to do something similar, and then looked at the two spools of wire that I was about to unwrap. They are already coils, so shouldn't I be able to just hook them up to an aligator clip and stick this to my whip antenna? (I am now thinking about taking the wire off of the smaller spool and adding it to the larger. Shouldn't that work?) And if I leave the wire on the spools (which are plastic) couldn't I turn them toward or away from the station of interest to further improve reception? (I could even put this in my attic, gaining a few feet of elevation and hiding it from my unappreciative wife.) Any input on any part of this idea is more than welcome. I would greaty value the opinions of those who have actually done something like one of these two options. Thanks, Dave ----== Posted via Newsfeed.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeed.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= 19 East/West-Coast Specialized Servers - Total Privacy via Encryption =--- |
#9
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"Brenda Ann" wrote in message ... "Dave" wrote in message ... Hmm. Okay. Only I don't have much outside space available. I *might* be able to manage 20-30 feet of random wire, but that is about it. And I have more than a mile of small-guage wire on these two spools. I was planning on wrapping it around a five-foot long piece of 4 inch PVC and standing it behind a closet door. Since my last last message I tried a very crude "hook-up" with one of the spools of wire and got absolutely no improvement in reception. Now I understand why, thanks to you good people. Back to the 20-30' piece of random wi my only option is to run it out the window and along the top rail of the fence in the back yard. Would this really outdo a massive broomstick antenna? Almost anything will outdo a broomstick antenna. 30' of longwire along your fence (presuming it is wood, and not steel) would do a great job. Even better still would be to run it around your rafters (presuming again that they are not concrete or aluminum siding or such). Either way, I would use some kind of standoffs (you can find them at hardware stores, or make your own from old thread spools). Okay, so here's the problem. The fence is metal, and the house is covered with steel siding. My DX-402 does pick up BBC on 5975 pretty well with just the whip (next to a window), but VOK is extremely weak to vanishing. (This last one is what I want the broomstick antenna for.) If I do go with the broomstick, should I stick with the five-foot piece that I already have cut, or go with a longer eight-foot piece which will still fit nicely in the corner I have in mind. Or should I go all out with a ten-foot piece (or even multiples maybe) and put it in the attic? Also, what type of ground should I use? I could run a ground wire out the window to a ground rod that is as old as the house, but that's about my only option (the house predates three-prong plugs with a real ground.) I really appreciate your thoughts on these things. You obviously know a lot more about this stuff than I do. Thanks, Dave |
#10
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In article , "Dave"
writes: Or should I go all out with a ten-foot piece of 4 inch PVC (or even multiples maybe) and put it in the attic? If the attic is non-metal, I'd try this solution .. |
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