[TowerTalk] Balun Recommendation

[Joe Subich, W4TV]

On 4/21/2012 3:38 AM, Steve Hunt wrote:
>
> Of course, the CM impedance "looking into" the coax braid at the
> feedpoint varies depending on the coax length: if the coax is well
> grounded at the shack end and is an odd multiple of a quarter-wave
> long, the CM impedance will be very high and you probably don't need
> a choke;

I would disagree with you there.  Coax lengths that are an odd multiple
of a quarter wave are the worst lengths for common mode problems in the
shack as they place the shack at a voltage maximum.  Proper grounding
will help but with so many shacks on the second floor or the opposite
end of the structure from the power (utility) entrance, obtaining
proper grounds is uncertain at best.

73,

    ... Joe, W4TV