Zac, Why guess?
You can find the antenna feedpoint impedance for various bands on L B Cebik's website (at least it used to be there) www.cebik.com . Armed with that information along with the known length of your feedline, use TLW which you can download from the ARRL website http://www.arrl.org/notes/9043/TLW3B.zip and feed the information into TLW to find your shack end impedance for each band of interest. A bit of cut 'n' try with TLW can find you the best compromise feedline length to ues with your antenna. 73, Don W3FPR > -----Original Message----- > > I'm sorry but I need to add this before Zac Brown does something > real stupid. When using 450 ohm feed line you must use this EXACT > length. The exact length is that which goes from the antenna to the > balun in your shack. > > Any talk about matching the 450 ohms is not correct. The feed line > runs with a very high SWR and since it is low loss there is just a tiny > loss. It will correct to a 1:1 SWR between your tuner and the radio. > > And about the balun. Seems if you have a 4:1 or 1:1 to choose from I > would choose the 1:1 because it does a better job of keeping the current > balanced in the balanced feed line. > > This is pretty complex stuff but you Zac do not need to do the math. > Just put it up and use it. I have been using it for 8 years now. Had to > get feed line. A hail storm just beat up my feed line :-) > > I have done the math. It takes several Smith Charts to plot the > current through the system. > > 73 Karl K5DI > > > > > Zac Brown wrote: > > So what's the best way to add some more line to the middle of my > > feedline? Is there a technique for joining two pieces of 450 ohm > > ladder line that doesn't create an imbalance in the line? Can I just > > leave one "leg" straight and then wrap the corresponding "leg" (on the > > other piece) other around it, then solder them together? Or should I > > just leave both legs straight and then solder them together? Or how > > about using those twist locks that you use for wiring up lights? > > > > This is probably a silly question, but I took great care to route the > > line away from anything that would imbalance it, and would hate to > > mess that up now. This is my first experience with balanced line :) > > > > Thanks, > > > > Zac > > KD5IEF > > K2# 4907 > _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
