[Elecraft] Balun for KX1 - doublet combo?

[Charles Greene]

Frank,

Order a F-50-43 core.  Take two #26 enamel insulated wires about 2' 
long.  Clamp the start for the pair with about 2" from the end, to the core 
with a cable tie.  Wind the pairs through the center.  Every time it passes 
the outside, run the pair through a piece of heat shrink tubing, as small 
as will take the pair and hit it with a heat gun.  Alternative, twist the 
wires together, not too tightly.  You can't tell the difference in 
performance.  Continue winding until you can't get any more turns 
on.  Clamp the end of the pair to the core with a cable tie with about 2" 
of pigtail.  Solder one pair to a BNC  male connector and put alligator 
clips on the other ends.  Guaranteed to be a good balun for the KX1.  You 
might check Tom Hammond N0SS's web site for some variations, mostly 
larger.  Last time looked, they were still there.  For the feed line, try a 
twisted pair of #22  stranded, insulated wire.  Not too tight on the twists 
or you will spend all day at it and it doesn't need it.  If you can find 
some teflon insulated silver plated stranded wire, so much the 
better.  It's not worth the difference which is mostly mechanical if you 
buy it new, but if you can guy some cheap like on eBay, go for it.  You can 
buy 300 ohm ladder line, but that takes the fun out of it.

For the K2 or K2/100, you should use a F-114-43 core and 15 turns.  That is 
good from 160 meters through 6 meters.

73,  Chas W1CG

At 02:39 PM 6/15/2005, Frank R. Oppedijk wrote:
>Hi,
>
>I've been lurking on this list for about a month now, so I guess this is 
>my official "hello" to the group. (Great group, BTW; excellent posts; am 
>learning a lot here!)
>
>In the meantime I've bought and assembled a KX1 and am now thinking about 
>which antenne should accompany it on my upcoming holiday to the Alps... 
>I'm considering buying one of those DK9SQ telescopic masts (as soon as 
>I've got a definitive answer about the mast being RF absorbent or not; I 
>want to be able to use it to put up a vertical too) so I can put up a 
>doublet antenna in inverted vee mode. I don't like the 3 dB loss from 10 
>meters (that's 33' for you non-metric people out there) of lightweight 
>RG174 coax, so I'm contemplating feeding with open wire.
>
>Now the big question: how to connect the symmetric open wire feeders to 
>the KX1?
>a) Don't bother; just plug one wire into the hot side and connect the 
>other side to the case
>b) Use a balun
>c) Something else.
>
>If b), then what configuration would you use? How small a toroid would 
>keep up with the torturing that it might get in such a high SWR environment?...
>
>Thanks in advance for all the help!
>
>Cheers,
>
>Frank