Unfortunately, the other part of my compromised situation is the shack location, which is at the other end of the apartment from the balcony. So I’m going to need 100 feet of coax to get to the radio. (Wife does not approve of radios in the living room!) That’s why I want to try to get the feedpoint impedance as close to correct as possible.
On the other hand, I’m on the 7th floor, with a reasonably clear view of the Atlantic ocean looking to the south. New Bedford, Massachusetts. :-) Doug. > On 28Sep, 2015, at 8:02 PM, Byron Servies <by...@n6nul.org> wrote: > > On Mon, Sep 28, 2015 at 4:37 PM, Douglas Hagerman > <douglas.hager...@me.com> wrote: > >> >> I have a space-limited dipole for 20 meters with drooping ends. The KAT-1 >> tuner >> will tune it. What I want to know is whether to use a 4:1 or 1:1 balun, or >> no balun, >> at the antenna. >> > > Are you feeding the antenna with coax or ladder line? > > Even a low dipole will have a feed point impedance of roughly 75 ohm, > so 1:1 would be fine with coax. You may want to consider a current > choke at the feed point, but that's up to you. > > With 450 or 300 ohm ladder line, a 4:1 would be more appropriate to > match the feedline to the expected impedance of the K1 input. > >> If the tuner reports 24 “x10” pF, is that 240 pF or 2.4 pF? A straight >> reading >> suggests that it’s 2.4 pF, but I don’t see how the tuner circuit can provide >> so >> little capacitance. But C4 (82 pF) plus C5 (150 pF) gives 232 pF which could >> 240 pF if you include some parasitic capacitance, maybe? > > Xc = 1/(2 * pi * 14 x 10^6 * 240 x 10^-12) ~~ 47. > > So, the tuner thinks it is seeing roughly 50 + j47 and needs -47 of > capacitance to balance it out, right? I'd go with the 1:1. > > 73, Byron N6NUL > -- > - Northern California Contest Club > - CU in the Cal QSO Party 3-4 Oct 2015 > - www.cqp.org ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
