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Frank Dresser wrote:
I recognized Telemon's antenna formula as something very much like the transmission line formula. I'm not sure how it applies to resonant receiving/transmitting end fed wires. If it does, I'd like to learn something. For a wire antenna, the field configuration near the wire is very similar to the field inside a coaxial cable. Unsurprisingly, it has similar behavior: the bulk of the energy tends to propagate along the wire and not radiate. This leads to Schelkunoff's approximation: you calculate the current distribution along the antenna as if it was a transmission line, and then calculate the radiation due to that current distribution. You can get the antenna impedance by calculating the impedance of a lossy transmission line (with loss equal to the radiation) with the assumed current distribution. You get the reception properties by reciprocity. Not only that, but the rocket scientists stay stuck on the ground! Good thing. Even when the rocket fails and destroys your payload, you get to go home and hug your wife and kids. It's happened to me twice so far (HETE-1 on a Pegasus in 1996, and ASTRO-E1 on a M-V in 2000). -jpd |
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