[Elecraft] Balanced solution for KAT500 tuner?

[Jim Brown]

On 9/30/2012 5:37 AM, goldtr8 at charter.net wrote:
> So am I correct in my understanding or just totally out in the weeds.

There may be more to it than that. First, no matter what feedline or 
matching system you use, there should be a serious common mode choke at 
the feedpoint.  Second, is this a single band loop, or a multi-band 
antenna?  The feedpoint impedance is likely to be very different on each 
band. A section of transmission line is often a better matching 
technique for single band antennas.  For a multi-band antenna, it would 
help to know the feedpoint Z on all bands and choose a feedline on that 
basis. The length of the line can also be an issue.  This is the sort of 
question that is best answered by constructing a simple model of the 
antenna using EZNEC. A stripped down version comes free with the ARRL 
Antenna Book, and is sufficient to model a simple loop at the level you 
need, and you can buy a more capable version for about $50.

One of the major reasons for choosing some feedline other than coax is 
that higher impedance lines have lower loss.  This matters a lot more 
for long runs than for short ones.  Decent 4:1 impedance transforming 
"baluns" are not cheap, and many hams would be better off spending that 
money on better coax.  400 ohm line may have much lower loss than coax 
if the feedpoint Z is 500 ohms, but coax may have much lower loss if the 
feedpoint Z is 10 ohms.

73, Jim K9YC