Topband: buried radial problems.

[Doug Waller]

>In general, you want the radiation resistance to be large compared
>to the other two (or the other two to be small in comparison to
>the radiation resistance). With a short antenna, you make the
>radiation resistance larger by making the antenna longer. You make
>the ground resistance smaller by using more radials and making
>them longer. You make the wire resistance smaller by using fatter
>wire.

Until recently, we were stuck with the low radiation resistance of a single 
vertical, 18-36 ohms.  My 60 ft tall tower with massive topload measures 18 
ohms and my poor, small-lot ground radials add another 10 ohms to that for a 
feedpoint impedance of 28 ohms.

But the Kinstar patent changes all the rules.  By separately feeding 4 to 6 
short verticals with individual coax feeds, the radiation resistance of each 
vertical wire increases substantially.  Radiation resistance can be 
represented by a ratio of voltage divided by current.  A higher radiation 
resistance indicates that higher voltages are present in each vertical wire, 
than in a single vertical structure.

A significant unnoticed advantage of the Kinstar design is that poor ground 
radial systems now play a much less significant role in the efficiency of 
the antenna.  While increased current can not fight the effects of a high 
resistance ground, increased voltage can, and DOES!

An EZnec model agrees, indicating much less loss of gain, as ground 
resistance is increased.  A disadvantage is that very large toploads are 
required for these short vertical cages.  All that additional current must 
have some place to go.

Happy Holidays,

Doug / NX4D