[Antennas] Carolina Windham

[Steve H]

Still collecting opinions from different hams. I have a thread open on 
Amfone:
http://amfone.net/Amforum/index.php?topic=46641.msg333566#msg333566

This is another response from K4SAV:

"The voltage mode balun used on a Carolina "Windom" is the thing that causes 
a lot of common mode current in the vertical section of the antenna before 
the choke.  Due to the voltage mode balun the feedpoint impedance of the 
antenna as seen by the coax is close to 50 ohms.  The wires being in the 
form of an OCF antenna creates resonances on other bands, although those 
resonances may not be exactly where you would like them.

Your antenna (with 75 ft of 300 ohm line) will also have a lot of common 
mode current in that 75 feet of ladderline due to the unbalance of the 
antenna wires, but it doesn't operate exactly the same.  The feedpoint 
impedance of the antenna becomes whatever the feedpoint impedance of the 
antenna wire is, translated by 75 feet of ladderline.   The SWR on 80 meters 
should move to just above the top of the band (maybe about 4.2 MHz) and be 
very high across most of the 80 meter band.  Probably about 70 to 1 at 3.6 
MHz.  You could tune the antenna wires to get a low SWR on 80 but the other 
bands will move too."

I most likely need to verify that the feed point mount up there is just a 
straight 300 ohm connect to the radials like my memory recalls.
I know this antenna is at least 10 yrs old, so its probably well recognized 
and there are pictures out there on the web somwhere of it.
I dont think it was modified in any way so there must be a reason it was 
configured with ladder line, not the coax.

Steve
KA2PTE