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#1
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AM Loop Antenna Design
I made a 15 inch square (broadcast band) loop antenna using 2 crossed
pieces of wood and about 14 turns of number 18 copper wire. I added spreaders in the center sections to increase the spacing between the windings and reduce the distributed capacitance. Works well and has a Q factor of 100 or more at 600 KHz. I get about 800mV from a local 50KW station. But the wire is concentrated around the outside perimeter of the loop and I'm wondering if there is an advantage in winding the loop so that the wire occupies more of the interior space. This would require a longer winding to maintain the same inductance and would further reduce the distributed capacitance, but would also increase the total resistance somewhat. Seems like a longer winding in the same space would produce a larger voltage, but at the expense of some additional resistance which may degenerate it somewhat. What would be the optimum given a 15X15 inch square space? -Bill |
#2
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AM Loop Antenna Design
On Mon, 14 Jul 2008 23:05:06 -0700 (PDT), Bill B
wrote: What would be the optimum given a 15X15 inch square space? Hi Bill, You are already there (or, rather, you are already so close that you wouldn't be able to tell the difference which would be a circle of 15 inch diameter). Subtended area counts for most. 73's Richard Clark, KB7QHC |
#3
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AM Loop Antenna Design
"Richard Clark" wrote in message ... On Mon, 14 Jul 2008 23:05:06 -0700 (PDT), Bill B wrote: What would be the optimum given a 15X15 inch square space? Hi Bill, You are already there (or, rather, you are already so close that you wouldn't be able to tell the difference which would be a circle of 15 inch diameter). Subtended area counts for most. 73's Richard Clark, KB7QHC If yer local to a 50kw station, why do you need an antenna all? Walt, W2DU |
#4
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AM Loop Antenna Design
Walter Maxwell wrote:
... If yer local to a 50kw station, why do you need an antenna all? Walt, W2DU Walter: Just guessing here, of course ... Maybe he wants to null out that 50kw stratosphere burner and hear another station on a on a cheaper radio on a close channel. LOL! Regards, JS |
#5
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AM Loop Antenna Design
On Jul 15, 6:03 am, "Walter Maxwell" wrote:
"Richard Clark" wrote in message ... On Mon, 14 Jul 2008 23:05:06 -0700 (PDT), Bill B wrote: What would be the optimum given a 15X15 inch square space? Hi Bill, You are already there (or, rather, you are already so close that you wouldn't be able to tell the difference which would be a circle of 15 inch diameter). Subtended area counts for most. 73's Richard Clark, KB7QHC If yer local to a 50kw station, why do you need an antenna all? Walt, W2DU I just use the local 50kw station as a reference. It's hard to see microvolts from some far away station on a scope, so I just use the big signals to make comparisons. I can see about 14 stations on a scope connected directly to the loop, but the amplitudes vary from a few millivolts to almost a volt. -Bill |
#6
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AM Loop Antenna Design
"Bill B" wrote in message ... On Jul 15, 6:03 am, "Walter Maxwell" wrote: "Richard Clark" wrote in message ... On Mon, 14 Jul 2008 23:05:06 -0700 (PDT), Bill B wrote: What would be the optimum given a 15X15 inch square space? Hi Bill, You are already there (or, rather, you are already so close that you wouldn't be able to tell the difference which would be a circle of 15 inch diameter). Subtended area counts for most. 73's Richard Clark, KB7QHC If yer local to a 50kw station, why do you need an antenna all? Walt, W2DU I just use the local 50kw station as a reference. It's hard to see microvolts from some far away station on a scope, so I just use the big signals to make comparisons. I can see about 14 stations on a scope connected directly to the loop, but the amplitudes vary from a few millivolts to almost a volt. -Bill hook a couple of them up to a rectifier and use them to charge batteries to power your radio. might as well make some use of that rf that is passing through you all the time! |
#7
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AM Loop Antenna Design
On Jul 15, 4:35 pm, "Dave" wrote:
"Bill B" wrote in message ... On Jul 15, 6:03 am, "Walter Maxwell" wrote: "Richard Clark" wrote in message . .. On Mon, 14 Jul 2008 23:05:06 -0700 (PDT), Bill B wrote: What would be the optimum given a 15X15 inch square space? Hi Bill, You are already there (or, rather, you are already so close that you wouldn't be able to tell the difference which would be a circle of 15 inch diameter). Subtended area counts for most. 73's Richard Clark, KB7QHC If yer local to a 50kw station, why do you need an antenna all? Walt, W2DU I just use the local 50kw station as a reference. It's hard to see microvolts from some far away station on a scope, so I just use the big signals to make comparisons. I can see about 14 stations on a scope connected directly to the loop, but the amplitudes vary from a few millivolts to almost a volt. -Bill hook a couple of them up to a rectifier and use them to charge batteries to power your radio. might as well make some use of that rf that is passing through you all the time! Actually, I use a 20 watt solar panel to charge batteries that power a car radio in my bedroom. At 12 cents a KWH, I figure I save 12 cents in 50 hours under good conditions, but I don't leave the panel outside all the time, just when the batteries get weak. It's good exercise dragging the solar panel out from under my bed and putting it out in the sunshine, and then putting it away again. It weighs about 17 pounds. -Bill |
#8
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AM Loop Antenna Design
Bill B wrote:
"What would be the optimum given a 15x15 inch square space?" Terman`s 1955 opus on page 929 says: "In particular, a loop antenna responds much less to the electric induction field than does a simple wire antenna of comparable intercept area. This is of importance because electric induction fields predominate in the man-made noise that causes disturbances in padio receivers, and this explains in part the popularity of loop antennas in broadcast receivers. Best regards, Richard Harrison, KB5WZI |
#9
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AM Loop Antenna Design
Richard Harrison wrote:
Bill B wrote: "What would be the optimum given a 15x15 inch square space?" Terman`s 1955 opus on page 929 says: "In particular, a loop antenna responds much less to the electric induction field than does a simple wire antenna of comparable intercept area. ... Best regards, Richard Harrison, KB5WZI Can't most of that be accounted for with the loops directional properties? And, that is just another way of stating the importance of the loops directional properties? Regards, JS |
#10
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AM Loop Antenna Design
John Smith wrote:
Richard Harrison wrote: Bill B wrote: "What would be the optimum given a 15x15 inch square space?" Terman`s 1955 opus on page 929 says: "In particular, a loop antenna responds much less to the electric induction field than does a simple wire antenna of comparable intercept area. ... Best regards, Richard Harrison, KB5WZI Can't most of that be accounted for with the loops directional properties? And, that is just another way of stating the importance of the loops directional properties? Regards, JS I think it's more an issue with being in the "near field" of the interference source, and/or the interference source being in the near field of the antenna. So the relationship between the E and H fields isn't the free space 377 ohms. More of the energy of the interference source might be in the H field than the E field, and the antenna may be more sensitive to the E field than the H field, or vice versa. |
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