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#1
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Best MW radio and antenna
Greg wrote:
"Sea gain"? Sounds interesting - please explain. Once while vacationing on the shore of the Gulf of Mexico, Anna Maria Island, Florida, I was pulling in all kinds of DX at night on the 20 meter ham band on my Radio Shack DX-440 portable - much more than I ever did at home (inland). The effect is far more dramatic on the MW band! MW propagation is greatly affected by ground conductivity. FCC regulation 73.190 (figure R3) is a chart of ground conductivity for the United States. In New England and the NYC area where MW propagation is notoriously poor, it ranges from 0.5 to 2mmho/m. Here in the South where it isn't much better, figures run between 2 and 8. (that includes Florida) In North Dakota where a single 5kw station can cover the whole state, figures between 15 and 30 are common. The chart considers the "ground" conductivity of seawater to be 5000mmho/m. (yes, that's 200 times better than the best land) Two examples of direct observation: - Wilmington, NC, at night. Car radio in the beach parking lot: Jamaica blasting in at entertainment quality on 760 and several other frequencies. I start driving inland; within a block the signals are noticably weaker. Within a mile, they're barely audible. When I get back to my motel about five miles inland, Jamaica is totally gone. - Massachusetts, high noon, car radio about five miles inland west of Newburyport. CHTN-720, Prince Edward Island, local quality. Drive about 20 miles inland to Andover; CHTN gradually fades into nothingness. Interesting that you observed this on 20m. Maybe less local interference? The ground conductivity shouldn't have much effect on shortwave -- greater *distances* (i.e., being within maybe 200 miles of the Atlantic in Florida, rather than being within 900 miles here in Tennessee) should make a big difference but I wouldn't think the difference between Tampa and a Gulf island would be that dramatic. -- Doug Smith W9WI Pleasant View (Nashville), TN EM66 http://www.w9wi.com |
#2
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Best MW radio and antenna
I am only about two hundred something miles from Pensacola,florida.That
married Irish woman calls Pensacola,,, Peniscola. cuhulin |
#3
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Best MW radio and antenna
In article ,
Doug Smith W9WI wrote: Greg wrote: "Sea gain"? Sounds interesting - please explain. Once while vacationing on the shore of the Gulf of Mexico, Anna Maria Island, Florida, I was pulling in all kinds of DX at night on the 20 meter ham band on my Radio Shack DX-440 portable - much more than I ever did at home (inland). The effect is far more dramatic on the MW band! MW propagation is greatly affected by ground conductivity. FCC regulation 73.190 (figure R3) is a chart of ground conductivity for the United States. In New England and the NYC area where MW propagation is notoriously poor, it ranges from 0.5 to 2mmho/m. Here in the South where it isn't much better, figures run between 2 and 8. (that includes Florida) In North Dakota where a single 5kw station can cover the whole state, figures between 15 and 30 are common. The chart considers the "ground" conductivity of seawater to be 5000mmho/m. (yes, that's 200 times better than the best land) Two examples of direct observation: - Wilmington, NC, at night. Car radio in the beach parking lot: Jamaica blasting in at entertainment quality on 760 and several other frequencies. I start driving inland; within a block the signals are noticably weaker. Within a mile, they're barely audible. When I get back to my motel about five miles inland, Jamaica is totally gone. - Massachusetts, high noon, car radio about five miles inland west of Newburyport. CHTN-720, Prince Edward Island, local quality. Drive about 20 miles inland to Andover; CHTN gradually fades into nothingness. Interesting that you observed this on 20m. Maybe less local interference? The ground conductivity shouldn't have much effect on shortwave -- greater *distances* (i.e., being within maybe 200 miles of the Atlantic in Florida, rather than being within 900 miles here in Tennessee) should make a big difference but I wouldn't think the difference between Tampa and a Gulf island would be that dramatic. Interesting topic. I wish I had tried MW DXing. Less local interference is most likely at least part of my improved reception on SW. And I live in Lakeland, another 35 miles inland from Tampa. Greg |
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