[Elecraft] Twinlead feedline to my K1

[George, W5YR]

Just a tack-on comment since Ron didn't mention this point:

In an installation of this sort, a 1:1 current or choke balun will
generally prove more successful than a 4:1 current or voltage balun. The
input impedance of the twinlead will swing wildly over the different bands
and on some bands a 4:1 balun will just make things a lot worse than they
already are. Occasionally it can work the other way, but it seldom seems to
happen very often. 

The 1:1 baluns operate independently of the line input Z and frequency
whereas the 4:1 transformer action is highly dependent upon frequency,
load, etc. The 4:1 voltage balun was once the workhorse but it has fallen
from favor as its shortcoming were discovered. The current balun is now to
be preferred, and the 1:1 version appears to work best in your application.

73/72/oo, George W5YR - the Yellow Rose of Texas         
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe   
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735
Icom IC-756PRO #02121  Kachina 505 DSP  #91900556  Icom IC-765 #02437


Ron D'Eau Claire wrote:
> 
> I'm cornsiderating upon putting up a NB6Zep antenna
> ( http://home.teleport.com/~nb6z/nb6zep.htm ), and I'm
> not sure how to connect the twinlead to my K1, which
> has an internal autotuner...
> 73/72/oo,
> 
> Lloyd, K3ESE
> 
> As the web site mentions down near the bottom, the easiest way to
> connect the feeder to an "unbalanced" output like your K1 is by using a
> "balun" or "balanced to unbalanced" transformer. The NB6Zep is a
> conventional "doublet" fed at the center with open wire line. Many Hams
> refer to these antennas as dipoles, although "dipole" usually refers to
> an antenna that is 1/2 wavelength long.
> 
> Using a balun at the transmitter will provide balanced" push-pull"
> currents for each side of the feed line. That will minimize radiation
> from the feed line, because the r-f fields created by each wire in the
> feeder will cancel each other out. That means that virtually all of the
> radiation will take place from the horizontal wire up in the clear.
> 
> You can buy baluns from many sources and instructions for making your
> own are in almost any book on ham antennas. On line check out
> http://www.hard-core-dx.com/nordicdx/antenna/feed/4_1balun.html or
> http://www.bytemark.com/products/kit_bal1.htm. I got these with a quick
> peek with an internet search engine. If you search on "balun" you'll be
> inundated with info! Keep in mind that baluns are used in many places,
> not just transmitters. You want a "transmitting" balun, not one designed
> for television or some other small signal use. With this type of
> antenna, the impedance at the balun will vary widely over the various
> bands and r-f voltages and currents can be very significant, even at QRP
> power levels.
> 
> Be sure to keep the feed line away from objects, especially any metal. A
> distance of 2 or 3 times the spacing between the feedline wires is
> usually adequate.