Topband: Ground system quiz

[Björn Mohr]

Having a bad performance in the ARRL 160m contest yesterday I decided  
to check my TX antenna today. I needed to adjust the un-un for a  
better match resulting in lower SWR so I can run full power.

As a little quiz, guess my ground system :)

Antenna: 18 meter top loaded vertical with a three wire hat attached  
at 15m and sloping 45 degrees.
Impedance: 12.5 Ohm
Feed: un-un to transform to 50 Ohm
Bandwith: 30 kHz, at SWR 2:1.
Terrain: Rocky on the shore of the Baltic Sea

73 de Björn,
SM0MDG
SE0X