[Elecraft] BL2 w/Multi-Band Dipole

[Jim Dunstan]

At 09:13 AM 4/2/2012 -0700, you wrote:



>Hello Everyone!
>
>I am planning on building a multi-band dipole fed with 450 Ohm ladder line
>soon.  I have a K1 & K2, both with the ATU's installed, and the BL2
>switchable balun.  I was wondering if I could connect the balun directly to
>the back of the K1/K2 when I use this antenna?  My other option would be to
>use one of my 18" foot RG8X jumpers between the rig and the balun.  I know
>someone here has done it, or at least knows whether this will work or not.
>I am also posting this question to QRP-L, so I apologize if you see this
>message twice.
>
>Thanks ES 73,
>
>David
>KC9EHQ

Hi David

When feeding a multi-band dipole with parallel feed line the first choice 
is to bring the feed line all the way to the ATU or balun at the operating 
position.  If the feed line is properly dressed (that is, care is taken to 
maintain balance) there will very little RF radiation from the feed 
line.  Since you are running QRP this strategy is further re-enforced ... 
since you want maximum efficiency.  The farther you separate the balun from 
the operating position with coax the greater will be the RF loss due to the 
characteristic of coax cable.  The usual reason for this separation is the 
difficulty that is often encountered in bringing the parallel line into the 
shack.

One tip on easing the parallel feed line from outside house to the 
operating position is to transition the 450 ohm feed line to 300 ohm twin 
lead the short distance to the balun connected to the radio.  The 300 ohm 
twin lead is not as efficient at the 450 ohm line but much more efficient 
than making the transition with coax.

Jim, VE3CI