[Elecraft] KX1 Antenna Idea

[Charles Greene]

Dan,

Here's another idea.  Use a short length of coax like 1' or less of RG-58 
or better RG-174, and put some ferrite beads around the coax to make a 1:1 
balun.   On the antenna side it is balanced, so solder this to the ladder 
line.   I hope you are at least using the small 300 ohm ladder line for 5 
watts.   If the feedline is small enough; #22 or smaller twisted pair, you 
can use the beads right over the feedline as a 1:1 balun.  I have made up 
some feedline using #28 teflon insulated solid wire wrap wire held together 
with heat shrink tubing.  The characteristic impedance is not important and 
it is low loss.  I measured some #26 twisted pair once and it's impedance 
is about 180 ohms.

In this application, a 1:1 balun works as well as a 4:1 balun.  A 1:1 balun 
can be made up using a pair of #28 magnetic wire and a F-50-43 1/2" ferrite 
tordal core.  Wind 10 turn of the wire pair on the core and secure both 
ends with wire wrap ties.  Alternatively, you can use RG-174 instead of the 
wire.  It usually takes a somewhat larger core, like a F-82-43 .825" core 
in order to get enough turns to work well on 40; or use a F-50B-43 core and 
fewer turns.  I have made lots of these small 1:1 baluns and my favorite is 
one using a F-82-43 core and as many turns of RG174 as you can get on it.

On my KX1, I use a 8' length of RG-58 soldered directly to one side of a 
42' antenna and a 8' counterpoise soldered to the coax shield for a 
portable antenna.  The other end has a BNC plug for the KX1.  Works well 
for a portable.  Doesn't beat an inverted V at 30' though, so you are on 
the right track.

At 09:08 PM 9/9/2005, Dan Romanchik wrote:
>Hi again--
>
>Last night, I worked a guy who also is a KX1 owner, and we got to talking 
>about antennas. I mentioned that while the antenna suggested in the 
>antenna tuner manual (24-28-ft. driven element with a 16-ft. counterpoise) 
>tunes up OK, I was kind of disappointed in the performance. The other guy 
>mentioned that he uses a 40-meter doublet, usually in an inverted vee 
>configuration, fed with ladder line, and that it tunes up well on all 
>three bands.
>
>I asked him whether or not he used a balun, and he said no, he just fed it 
>directly into the radio. I suppose his antenna could be fairly 
>well-balanced or that the KX1 is able to tolerate a fair amount of imbalance.
>
>Whatever the case, I was thinking that it shouldn't be too difficult to 
>build a small balun--and it really could be a small one since the maximum 
>power level it needs to handle is just 5W--into a small plastic project 
>box. On one end, the box would have two binding posts to connect the 
>ladder line, and a panel-mount male BNC (if they make such a thing) on the 
>other.
>
>Does this seem reasonable to do or is it overkill?
>
>73!
>
>Dan KB6NU