[Elecraft] KX3 - Balun

[w0ih]

Steve,

I was intrigued by the use of the BNC connector on the balun enclosure.  I
had never thought of that.  I was just going to use a short coax cable
between the KX3 and my new home-brew balun.

I built a balun a couple weeks ago using a 1"x2"x3" box from Radio Shack
($3) and a T130-2 core and #18 gauge magnet wire off ebay or under $10.  I
wanted something to match a higher impedance of a W3EDP antenna, so I used a
balun design by W2FMI using 4 wires (essentially two 4:1 baluns) on the core
and tapped for 16:1, 9:1 and 4:1 (I also tapped off the half coil sides for
2:1, 6:1 and 12:1 (approx).  I used a RadioShack 6 position rotary switch
($3).  I then marked the switch positions as 100, 20, 300, 450, 650 and 800. 
Input is a BNC (female) and output is a pair of banana sockets.  It was a
bit of a tight fit, but seems to work out OK. 

Testing with an MFJ259B and rf voltmeter shows a progression of voltage
output as I switch through the positions.

I wanted to use the balun for a W3EDP antenna
(http://www.zerobeat.net/g3ycc/w3edp.htm) so I need a higher impedance
output.   I have another version of the same balun that I built using an
Amidon 2kw core, but it was too large to carry around for the KX3 in my
portable case (I use an old video camera case that carries everything). 

The larger version of the balun worked just fine when I used it with the KX3
and internal tuner.  Just change impedance tap positions until I get a good
match with the tuner.   I haven't actually tried the new balun yet though. 
I may modify it to use the BNC connector like you have implemented.

I have some pictures, but not sure where to upload them to. 

Mike
  W0IH



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