I am relatively new to this Forum and have been seeking information about Taranis X9D plus 2019 and the FrSKY RX6R receiver.
Trying to be very graceful in how I say this; a more unified use of "dB" in our discussions would be very helpful.
Wikipedia has a wonderfully detailed page on the subject and shows the small but important differences between terms like dB, dBm, dBw, and a collection of antenna specific units.
en.wikipedia.org
An even better description is found in "Introduction to Airborne Radar" George Stimson. There are several different revisions and all are very useful. Besides having an excellent discussion of dB, George does a really good job of describing antenna performance. He uses pictures and drawings to explain the concepts without resorting to trying to describe things with Maxwell's equations, Friis or the like. Early on Hughes published this book and only let employees or their customers have copies. Guess what, antenna performance is really important in radars. George was a proposal manager at Hughes and spent years learning how to explain how their radars worked so customers would buy from Hughes and not someone else. I did not want to copy sections from Georges book out of respect for his great work but it is now widely available for modest prices.
About antennas: Antennas are passive devices and thus do not ever transmit more power than they're given. Gain (and directivity) are measures of the pattern shape and the ability to focus power in a particular direction, hence to often cited positive numbers of gain. dB units are almost (almost, almost ) always used to describe antennas. Positive gain numbers do not imply that more power is radiated than delivered. In the context here, the characteristics do not change if an antenna is used to transmit or receive. Another important measurement relates to how much of the power delivered to the antenna is actually absorbed to be radiated. Various terms are used to describe this including VSWR, reflection coefficient, s11, matching and the like. The idea is that good antennas do not reflect much of the delivered power. Bad antennas do reflect power and thus little is left to radiate. A good match (low reflection) is necessary for good antenna performance but it does not guarantee that the antenna will be useful. A -10 dB attenuator has a good match for example but it is a rotten antenna. Antenna matching is hardly ever mentioned here. By the way, two or more of those metal things are antennas, antennae are two or more long pointy things one finds on cockroaches. At least, that is the common usage in American English. British English journals do not always use the same convention.
Those little connectors used on the models, Hirose U.Fl, and the like are very fragile and wear out after a small number of mate and break cycles. Handle them carefully and infrequently.
Trying to be very graceful in how I say this; a more unified use of "dB" in our discussions would be very helpful.
Wikipedia has a wonderfully detailed page on the subject and shows the small but important differences between terms like dB, dBm, dBw, and a collection of antenna specific units.
Decibel - Wikipedia
An even better description is found in "Introduction to Airborne Radar" George Stimson. There are several different revisions and all are very useful. Besides having an excellent discussion of dB, George does a really good job of describing antenna performance. He uses pictures and drawings to explain the concepts without resorting to trying to describe things with Maxwell's equations, Friis or the like. Early on Hughes published this book and only let employees or their customers have copies. Guess what, antenna performance is really important in radars. George was a proposal manager at Hughes and spent years learning how to explain how their radars worked so customers would buy from Hughes and not someone else. I did not want to copy sections from Georges book out of respect for his great work but it is now widely available for modest prices.
About antennas: Antennas are passive devices and thus do not ever transmit more power than they're given. Gain (and directivity) are measures of the pattern shape and the ability to focus power in a particular direction, hence to often cited positive numbers of gain. dB units are almost (almost, almost ) always used to describe antennas. Positive gain numbers do not imply that more power is radiated than delivered. In the context here, the characteristics do not change if an antenna is used to transmit or receive. Another important measurement relates to how much of the power delivered to the antenna is actually absorbed to be radiated. Various terms are used to describe this including VSWR, reflection coefficient, s11, matching and the like. The idea is that good antennas do not reflect much of the delivered power. Bad antennas do reflect power and thus little is left to radiate. A good match (low reflection) is necessary for good antenna performance but it does not guarantee that the antenna will be useful. A -10 dB attenuator has a good match for example but it is a rotten antenna. Antenna matching is hardly ever mentioned here. By the way, two or more of those metal things are antennas, antennae are two or more long pointy things one finds on cockroaches. At least, that is the common usage in American English. British English journals do not always use the same convention.
Those little connectors used on the models, Hirose U.Fl, and the like are very fragile and wear out after a small number of mate and break cycles. Handle them carefully and infrequently.
