So let's say I wanted to set up a part 15 AM transmitter on a site in the linked photo...
http://picasaweb.google.com/PianoPl...key=Gv1sRgCIer0efojpPg8AE#5501810777831424738
The property corners are marked on the image, and there is a distance scale on the lower left. The arrow marks where I do a lot of my outdoor DXing, and the transmitter site would probably be within several feet of that (although if another spot would work better, I would consider that). There is a general downhill slope north to south on the property, with a flat portion east of the arrow from about 7-10 feet south of the pool fence to about 15-25 feet or so north of the south property fence. There are septic tank leech lines underground in that area, and there was also sprinkler irrrigation as well, but it's not currently in use. (There had formerly been grass and several fruit trees in that area.) According to the FCC ground conductivity map, that is in an area where the conductivity is 8 mS/m.
Considering the limited amount of space, what would be a recommended ground system to use? Also how far would I expect the signal to go, if it's properly set up? BTW, on my Tecsun PL-380, which is probably a few dB less sensitive than R. Fry's PL-310, I can faintly hear 960 KIXW, being about 30% outside their 150 µV/m contour. The RSSI on my PL-380 is about 30dBuV there. In the upper portion of the band where I would likely transmit, the blank-channel indicated signal is 20-24dBuV on the PL-380. (In Campo, CA, I can hear 1090 XEPRS in the daytime with a weak but usable signal, even though that's about 3 times as far as the 0.5mV/m signal shown on the night pattern map (which the station uses full time). Indicated RSSI in that area on blank channels is approximately 15dBuV there.) The typical "noise floor" (indicated RSSI on unoccupied channels) is around 30dBuV across much of the lower portion of the band, although it dips to around 15-17dBuV at 520kHz, and peaks at around 43-45dBuV around 1150kHz, due to a 50kW (daytime) station 9 miles away on 1170 and a 10kw station 6 miles away on 1130. At night I get a "noise floor" up to 41-43dBuV from 740 to 780 due to a 50kW (nighttime) station 7 miles away on 760. My PL-380's specified sensitivity, according to the specs in the back of the manual, is 1mV/m with a 26dB SNR.
As for the close-in signal, like in the yard and in the house (east of the transmitter site - north is up in the photo), would it be too unreasonable to expect a 63dBuV indicated signal on my PL-380 throughout the entire property, with the signal possibly being strong enough to de-sensitize my PL-380 so it indicates 50dBuV several channels off the transmitter's frequency? Could I get a 63dBuV indicated signal (the max that my PL-380 will display) at the opposite corner of the elementary school campus about a thousand feet or a little more to the west / northwest?
Also, under a different rule, how would I calculate the transmitter power necessary to achieve a particular field strength at a particular distance, like 15,848 µV/m @ 30 meters at 13,560 kHz, using an electrically very short antenna? I've heard a figure of 4.8 milliwatts using a half-wave dipole, or a quarter-wave vertical over a ground plane. I would, however, be using an antenna that's a very tiny fraction of that length, without much of any ground, save for the chassis of the transmitter, or maybe the table or chair or other small metal object on which it is sitting, as it would be used indoors or in other very small spaces much of the time it's used. Also, how would I set it up indoors to mostly use direct wave, so I get the inverse distance field strength loss (31,696 µV/m @ 15 meters, 15,848 µV/m @ 30 meters, 7,924 µV/m @ 60 meters, 3,962 µV/m @ 120 meters, 1,981 µV/m @ 240 meters), rather than have the much faster groundwave absorption? I realize that I would mostly be limited to line of sight, although I can hear an FM station 212 miles away from Santa Barbara. I of course won't be expecting a range like that from this setup, though, as KVYB 103.3 is 105kW with a quite high antenna, and this would be a tiny fraction of that power within a few feet of ground level, usually in a flatland area or in a vallley.
Also, once or twice a year I may be at the Tulare County Fairgrounds for a few days (look them up on Google maps to get an idea where it is (in Tulare, CA) and how big it is. If an FM transmitter is operating from inside the largest white-roof building, would it be possible to legally have at least a 63dBuV indicated signal on the PL-380 throughout most of the fairgrounds property (not necessarily including the race track to the south - 48-54dBuV would be more than sufficient there)?
http://picasaweb.google.com/PianoPl...key=Gv1sRgCIer0efojpPg8AE#5501810777831424738
The property corners are marked on the image, and there is a distance scale on the lower left. The arrow marks where I do a lot of my outdoor DXing, and the transmitter site would probably be within several feet of that (although if another spot would work better, I would consider that). There is a general downhill slope north to south on the property, with a flat portion east of the arrow from about 7-10 feet south of the pool fence to about 15-25 feet or so north of the south property fence. There are septic tank leech lines underground in that area, and there was also sprinkler irrrigation as well, but it's not currently in use. (There had formerly been grass and several fruit trees in that area.) According to the FCC ground conductivity map, that is in an area where the conductivity is 8 mS/m.
Considering the limited amount of space, what would be a recommended ground system to use? Also how far would I expect the signal to go, if it's properly set up? BTW, on my Tecsun PL-380, which is probably a few dB less sensitive than R. Fry's PL-310, I can faintly hear 960 KIXW, being about 30% outside their 150 µV/m contour. The RSSI on my PL-380 is about 30dBuV there. In the upper portion of the band where I would likely transmit, the blank-channel indicated signal is 20-24dBuV on the PL-380. (In Campo, CA, I can hear 1090 XEPRS in the daytime with a weak but usable signal, even though that's about 3 times as far as the 0.5mV/m signal shown on the night pattern map (which the station uses full time). Indicated RSSI in that area on blank channels is approximately 15dBuV there.) The typical "noise floor" (indicated RSSI on unoccupied channels) is around 30dBuV across much of the lower portion of the band, although it dips to around 15-17dBuV at 520kHz, and peaks at around 43-45dBuV around 1150kHz, due to a 50kW (daytime) station 9 miles away on 1170 and a 10kw station 6 miles away on 1130. At night I get a "noise floor" up to 41-43dBuV from 740 to 780 due to a 50kW (nighttime) station 7 miles away on 760. My PL-380's specified sensitivity, according to the specs in the back of the manual, is 1mV/m with a 26dB SNR.
As for the close-in signal, like in the yard and in the house (east of the transmitter site - north is up in the photo), would it be too unreasonable to expect a 63dBuV indicated signal on my PL-380 throughout the entire property, with the signal possibly being strong enough to de-sensitize my PL-380 so it indicates 50dBuV several channels off the transmitter's frequency? Could I get a 63dBuV indicated signal (the max that my PL-380 will display) at the opposite corner of the elementary school campus about a thousand feet or a little more to the west / northwest?
Also, under a different rule, how would I calculate the transmitter power necessary to achieve a particular field strength at a particular distance, like 15,848 µV/m @ 30 meters at 13,560 kHz, using an electrically very short antenna? I've heard a figure of 4.8 milliwatts using a half-wave dipole, or a quarter-wave vertical over a ground plane. I would, however, be using an antenna that's a very tiny fraction of that length, without much of any ground, save for the chassis of the transmitter, or maybe the table or chair or other small metal object on which it is sitting, as it would be used indoors or in other very small spaces much of the time it's used. Also, how would I set it up indoors to mostly use direct wave, so I get the inverse distance field strength loss (31,696 µV/m @ 15 meters, 15,848 µV/m @ 30 meters, 7,924 µV/m @ 60 meters, 3,962 µV/m @ 120 meters, 1,981 µV/m @ 240 meters), rather than have the much faster groundwave absorption? I realize that I would mostly be limited to line of sight, although I can hear an FM station 212 miles away from Santa Barbara. I of course won't be expecting a range like that from this setup, though, as KVYB 103.3 is 105kW with a quite high antenna, and this would be a tiny fraction of that power within a few feet of ground level, usually in a flatland area or in a vallley.
Also, once or twice a year I may be at the Tulare County Fairgrounds for a few days (look them up on Google maps to get an idea where it is (in Tulare, CA) and how big it is. If an FM transmitter is operating from inside the largest white-roof building, would it be possible to legally have at least a 63dBuV indicated signal on the PL-380 throughout most of the fairgrounds property (not necessarily including the race track to the south - 48-54dBuV would be more than sufficient there)?