[TowerTalk] Baluns...just one more time.

[Jim Thomson]

Ok, what is the consensus on grounding the braid of the coax,  on the 
xcvr side of any feed point balun ??    I see that W8JI uses solenoid
type HF yagi bauns... with 10-20 turns of 213-U..wound in a solenoid
fashion...on a 4 inch ID.   He also immediately bonds the braid to the
boom... on the xcvr side of the solenoid balun.     If it was a monobander,
ideally you would want to bond the braid a physical quarter wave back
from the feedpoint.   That’s not always practical, and a lot of folks use
multiband yagis.   So what about bonding the braid, either just on the xcvr
side of the balun.... or within a few feet of the balun ?    The idea here is
then the bonding point is well less than a quarter wave away from the 
feedpoint.... and CM should be reduced somewhat. 

Steve, G3TXQ depicts CM current on a 20m dipole... with and without
a balun... for various coax lengths.   But his range is just 20-70 feet.  A
qtr wave on 20m is 17.5 feet.....so CM would be nothing.   Its also nothing
at 3 x qtr waves..or 52.7 feet.   Ok, what happens when LESS than a qtr wave 
is used.....or if braid is bonded to boom..within 0-.25 wavelengths of the 
xcvr side of the balun ?? 

Jim   VE7RF