[Elecraft] BL-2 Balun Heating

[Jim Dunstan]

At 10:02 PM 11/19/2009 -0500, you wrote:
>I recently built a BL-2 Balun.  It is connected between my Palstar AT1KM
>tuner and my doublet antenna.  The antenna consists of a 100' wire up
>25' and fed by 95' of 600 ohm open wire feeder.  I'm using the 1:1
>setting on the balun.  There is a 4" section of RG-213 between the balun
>and a coax input of the tuner.  I'm driving it with 125 watts from a
>TS-850.   After no more than a few minutes of CW or RTTY transmission,
>the balun is too hot to touch, the SWR rises and the power goes down.
>The balun is obviously saturated.
>
>Does anyone have an idea how I can reduce the overheating?  I've tried
>adding a heat sink but it doesn't make any difference.
>
>Tnx for reading!
>
>Gary  N2UM

Hi Gary,

You could place the balun (in the 1:1 configuration) on the other side of 
the tuner ... that is between the xcvr and the tuner.  One side of the 
balun output would connect to the center pin of the input coax connector 
and the other side of the balun output connects to the tuner ground 
(frame).  The tuner frame would of course be isolated from any ground 
especially the radio.  The output of the tuner (no balun on the output) 
would connect directly to the 600 ohm feed line ....  one side of the line 
connects to the center of the coax output center pin and the other side of 
the line connects to the tuner ground.

The arrangement will work perfectly as a balanced tuning arrangement for 
the feed line and at the same time place the balun where it should be .... 
in the low impedance 1:1 circuit point ... with the result it will operate 
with efficiency and be cool as cucumber.  At the moment it is not a 'balun' 
problem ... but a circuit problem.

Jim, VE3CI