> How does modeling with 450 Ohm window lead work out? That would suggest > a 9:1 balun.
Someone earlier (K2VCO, I believe) cautioned against falling into the trap of believing that the characteristic Z of the line is always the impedance actually present at the end of the line. The Z seen at the line end is determined by several factors, including the magnitude of the line-to-load (mis)match, type of feedline, and feedline length. For multi-band wire antennas, the line input Z can range from less than 10 ohms with some short antennas to over 5K ohm. These numbers appear at the line input. Just because it may be "450-ohm line" does not mean that's the target Z to tune and match. The only time 450-ohm line presents a 450-ohm impedance at the line input regardless of distance, is when the characteristic Z of the line equals the load Z and line loss is small. In the case of the folded dipole for mono-band operation, the antenna feed-point Z can easily be made 300 ohms with little or no reactance with a bit of antenna length pruning and perhaps slight height change. Feeding it only with a 300-ohm characteristic Z line makes best sense, since the Z at the line input, regardless of line length is going to be near 300-ohms at the cut operating frequency, with little reactance. Paul, W9AC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
