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Originally Posted by Elie
Why is this in remote sensing?
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It appears that Seden is attempting to discover a link between high voltage and long range locating. Perhaps he wonders if there is some frequency he can detect from a long distance with a spectrum analyzer while using equipment described in the patent. Why are you posting in remote sensing?
A number of experimenters have noted variations in AM broadcast frequency strength as they moved past large anomalies in the ground. A LRL which claims to work on this principle is manufactured by Vernell Electronics. They have units which send out a low-power AM radio signal in the UHF band, and use a loop antenna to survey the signal strength in a field in front of the transmitting antenna. The frequency they use is unknown, but Mike(Mont) says he read on a Chinese website that the VR1000B uses 400-3000 Mhz. I presume he means that the transmitter is adjustable to a series of preset frequencies in that range. Carl has one of these machines which he claims is a piece of crap. Dell Winders says he found the Vernell Electronics locators worked successfully for him on a boat, airplane and land searching until "operating conditions deteriorated affecting the reliability of the instrument making it impractical for my use in 1988". Dell never described what operating conditions deteriorated.
The Vernell Electronics machines come to mind because they are looking at AM signals as you intend to do, and they have defined a range of frequencies where they expect to find results, rather than a white noise source. Of particular interest is that Vernell uses a coil to broadcast the UHF signal rather than an antenna. He also uses a coil which is slightly smaller than a sheet of paper to survey the signal strength. In his newer VR5000, the coil is replaced by the "scan gun", which is probably a smaller coil and possibly other apparatus inside a plastic housing.
Note the range of frequencies Vernell uses are basically the UHF range, not the AM broadcast range. I suspect this is because the size of a UHF wave is closer to the target size than AM broadcast waves, and possibly this makes it easier to pinpoint a buried metal object. While Vernell sells locators that operate in the UHF range, I have read about experimenters who noted signal strength variations in the AM broadcast range as well as the FM broadcast range and short wave bands. I suppose these experimenters did not investigate the UHF band because this band had limited use at the time they did their experiments (they didn't have a spare adjustable UHF receiver lying around back in those days). Also, Dell has stated "conditions deteriorated". Perhaps you would have a more difficult time to detect the signal strength today than the experimenters back in the 60s. Consider that today, we are inundated with UHF noise that comes from everything from cell phones, microwave ovens and wireless LANs to radar installations. There are also references to environmental changes that happened about the time Dell described.
Be sure to look at the Vernell instruction manual section and the photos to get ideas how he uses his LRL equipment. Here is the website for Vernell Electronics products:
http://www.vrdetectors.com/products.cfm
Also check this forum thread for more details:
http://thunting.com/geotech/forums/s...ad.php?t=13089