Topband: 160 meter elevated vertical

[Tom W8JI]

> I'll be putting up a T-top elevated vertical for 160 in the next couple of
> days. The baser will be around 60 ft above ground and the Tee (about 40
> feet  long will be at about 170-180 ft...depending on the caternary sag. 
> There
> will be  4 radials at 90 degrees to each other.
>
> Question: Any type of balun necessary with this? Or is it good to go. I'm
> using RG58 to feed it to keep the weight low on the caternary to avoid say
> but  could wind something on a four inch PVC.

The goal of ANY common-mode choke is simply to make the path to ground along 
the outside of a cable look like a poor path compared to a ground or 
counterpoise at each end.  The common mode impedance, exciting source, and 
location of the choke dictate what is required.

All verticals with sparse ground systems need common mode isolation, unless 
something causes the feeder to look like a very high impedance compared to 
the path out to the radial to earth voltage. Your antenna base is around 
1/8th wave high, and I assume suspended in the clear vertically.

If you simply ground the coax shield to a reasonable earth ground at the 
earth surface, you will already have a pretty good CM choke for your system. 
The feeder itself will act like a choke. If you wanted to add anything, a 
little inductance anywhere along that cable shield (by coiling the cable) 
would make things better.

73 Tom