Topband: feeding a top loaded vertical

[pa5r]

Hello topbanders,
 
For our contest station we are currently upgrading our 160m setup with a
24m (73 ft) toploaded vertical antenna for TX only. The antenna is made
of aluminium, tapering from 85mm down to 50mm. The ground system is made
of 36 radials of 42m (126 ft) each connected at the base of the antenna.
The radials are on the ground. We use 8 x 7.5 m (22 ft) wires for
toploading, these are sloping down in a 60 degree angle from the
vertical. Can anyone here give us some advice on how to properly feed
the RF to this antenna. Our idea is to go for a gamma match, using a
vacuum capacitor at the base to tune out any present inductance. The
gamma rod would consist of a single wire about 0.5 to 1m spaced from the
antenna. The main question here is were to put the gamma tapping point
on the vertical. Any ideas on the feed and improving efficiency for this
system are welcome!
 
Thanks in advance!
 
73 Jelmer PA5R