When I was working, and had good equipment, I used to know the expected loss of a signal through the air at one mile. I will need help for an accurate figure now, but I think it was roughly 100 dB of loss.
According to Wikipedia the formula for free space loss is 20Log(distance) + 20log(frequency) - 27.55 where distance is in meters and frequency is in megahertz. That would put the loss at one mile (1610 meters) on 14 MHz right at 60 dB. 73, ... Joe, W4TV On 3/1/2013 2:35 PM, Richard Fjeld wrote:
Sam, I agree with Dale, WA8SRA, as he describes the skirts of a strong signal. I let that be assumed in my answer below. I don't remember if you stated whether you had calibrated your K3/P3 with a XG1,2,3, or something similar? That S9+60 makes me wonder. When I was working, and had good equipment, I used to know the expected loss of a signal through the air at one mile. I will need help for an accurate figure now, but I think it was roughly 100 dB of loss. If that is in the ball park, here is what you would see; If the people near you are transmitting at 400 watts of output, assuming unity gain and 100% efficiency in the antenna system, that is 56 dBm of power. (100 watts is 50 dB) If it loses 100 dB in the air and if all things are equal in your antenna system, you would measure about -44 dBm, or S9+30. (Not forgetting the accuracy of S-meters) Perhaps I am way off in my recall. If so, someone please correct this example. Rich, n0ce ----- Original Message ----- From: Richard Fjeld To: Sam Morgan ; [email protected] Sent: Friday, March 01, 2013 1:37 AM Subject: Re: [Elecraft] OT P3 question The way to resolve this is to compare to other signals. I see very nicely shaped signals with straight skirts within 3 KHz at times, and other signals that look like a pine tree. A nearby ham lives less than 2 miles from me and runs an amp. Sometimes his signal is clean, and sometimes he overdrives. And when I see it wide, others with SDR pan adapters 150 miles away see it too. So it isn't a close-distance thing. Now that he has an SDR pan-adapter, he is more conscious of signal width. Years back, we operated under the threat of getting a pink ticket if we erred. Rich, n0ce ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
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