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868MHz Propagation problem
On Oct 24, 2:26*pm, "Anthony Fremont" wrote:
Mark wrote: On Oct 24, 2:00 pm, "Paul Hovnanian P.E." wrote: wow so many of these replies are wrong.. This is normal when antenna "theory" comes up. in almost all cases, *RF path losses are RECIPROCAL. I agree, including the antenna gains (meaning that the antennas at each end don't have to match). (even a 1/2 silvered mirror is reciprocal to light) Well that guy is usually on a differet page. As some have said, the cause of your issue is probably interference to the outside receiver. That's what I think is the most likely cause. *The guy outside probably has his Nextel phone with him. *;-) Or maybe something about the indoor setup is causing the indoor Tx to operate at lower power. I suppose that's possible too. *The OP should make sure the power supplies are equivalent (meaning that the output power would suffer more than the receiver gain with a drooping supply). *So check the indoor supply. It is very unusual for RF path loss to be non-reciprocal.- Hide quoted text - - Show quoted text - It is assumed that the path to and from the office should be inferior to the line of sight path out on the street. This may or may not be true. The building may actually be offering gain in certain directions. I would start by seeing if the same condition existed at many more locations. If it does then other ideas need to be examined, I would start by examining the RF environment outside the building. Jimmie |
#2
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868MHz Propagation problem
Hello,
There should be a reciprocal relationship between the modules regardless of height, antennas etc. as long as TX power and RX sensitivity of the modules are the same (which they appear to be). The modules are unlikely to have very good input filters at 868MHz, so any adjacent channel interference (GSM etc.) is likely to cause the out of balance behaviour. Try heading in a different direction outside, or go somewhere else with your experiment. For your real world application, are you likely to have any site close to adjacent channel transmitters (cell or broadcast) ? If so, think about a decant front end filters. This could be costly, but might save you... Regards, Mark On Oct 25, 9:25*am, wrote: On Oct 24, 2:26*pm, "Anthony Fremont" wrote: Mark wrote: On Oct 24, 2:00 pm, "Paul Hovnanian P.E." wrote: wow so many of these replies are wrong.. This is normal when antenna "theory" comes up. in almost all cases, *RF path losses are RECIPROCAL. I agree, including the antenna gains (meaning that the antennas at each end don't have to match). (even a 1/2 silvered mirror is reciprocal to light) Well that guy is usually on a differet page. As some have said, the cause of your issue is probably interference to the outside receiver. That's what I think is the most likely cause. *The guy outside probably has his Nextel phone with him. *;-) Or maybe something about the indoor setup is causing the indoor Tx to operate at lower power. I suppose that's possible too. *The OP should make sure the power supplies are equivalent (meaning that the output power would suffer more than the receiver gain with a drooping supply). *So check the indoor supply. It is very unusual for RF path loss to be non-reciprocal.- Hide quoted text - - Show quoted text - It is assumed that the path to and from the office should be inferior to the line of sight path out on the street. This may or may not be true. The building may actually be offering gain in certain directions. I would start by seeing if the same condition existed at many more locations. If it does then other ideas need to be examined, I would start by examining the RF environment outside the building. Jimmie- Hide quoted text - - Show quoted text - |
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