Dean, Nice analysis. One can take it a step further. Assume your 3 foot RG-213 balun that dissipates about 8% of power or about 40W for 500W input. It would contain some 36 beads and would weight perhaps 2 pounds.
An input balun with identical choke impedance would be a single bead with 6 turns of RG-174. One foot of RG-174 has 1% loss at 30 MHz and 0.25% at 2 Mhz. Also RG-174 is rated 200W average at 30 Mhz and 750W at 2 MHz. Most likely it would carry 500W intermittent on 10m when matched. In this case, an output balun would weigh 36 times more, be 36 times more expensive, and have 8 times higher losses. Mind this is for extreme 3000 Ohm load. I would not use an input balun for large stationary setup because stray capacitances and switching would make it less efficient and cumbersome. I would use an output balun in portable situations because it is so much lighter, has so low losses, and one can have very large common impedance by adding extra turns. Ignacy, VK2/NO9E -- View this message in context: http://elecraft.365791.n2.nabble.com/Balun-at-input-or-output-of-tuner-tp7087668p7088210.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ 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
