That's a bad design for 40m because the input resistance is only about 3 ohms. The designer was concerned about the radiation pattern resembling a dipole on higher frequencies with little regard to matching.
Using a 4:1 balun would do the opposite of what you want to accomplish. 5 ohms is difficult for any tuner to match and can cause a lot of power loss in the circuit and with higher power, burn up a torroid coil! That balun would drop the impedance to an insane value. Generally a multiband doublet should be 1/2 wavelength on the lowest band. That's about 65 feet for 40m cw. Also that feedline that the author used no doubt has a rather low impedance which further complicates things. I'de guess it is about 100 ohms. Using 300 tv twin lead would help raise the Z for your tuner to about 15 ohms on 40m even with the 44' flat top. Try that first. If all else fails, tie the feeders together and feed it like a long wire against a counterpoise. Steve N4LQ ----- Original Message ----- From: "Burke Jones" <burkejo...@gmail.com> To: <Elecraft@mailman.qth.net> Sent: Friday, June 03, 2011 2:44 PM Subject: [Elecraft] KX1 + Tuner + Norcal Doublet >I constructed a Norcal Doublet using some speaker wire. It seems to > tune up fine on 20 meters using the internal KX1 tuner - but on 40 > meters I could not get the SWR under 4. > > Would a 4:1 balun help with this? > > Any links on how to build a simple balun using an aircore and not a > torroid? > > Thanks a bunch! > > Burke Jones > N0HYD > Olathe, KS > http://www.n0hyd.com > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
