3. Connection of coax cable
The feeding of the antenna is done by 50 Ohm coax cable.
For connection a PL-259 connector is required. The connector should be sealed against water entry.
Close to the feed point the cable should be winded to a choke coil with 5 to 6 turns of about 20 cm of
diameter. Hereby the antenna is electrically balanced and unwanted radiation of the cable itself is
prevented.
Instead of the choke coil a 1:1 balun can be used as well.
4. Adjustment of the antenna
An adjustment of the antenna is not necessary if the given dimensions are exactly observed.
By some influences of the direct surroundings it may happen that the resonance of the antenna (=point
of best SWR) shifts on one or several bands.
By minimum changes of the according driver lengths (=shortening or lengthening of the outer 12mm
sections, in case of 20m driver and reflector by the same amount) the resonant frequency of the
according band can be shifted to the desired point.
By a slight decrease of the lengths of both element halves (put outer section in to the last drill-hole) the
resonant frequency will be shifted upwards, by an increase (pull final section out to the first drill-hole) it
will be shifted downwards.
Normally these adjustments don’t have to be done as the antenna does not react very sensitive against
influences of the surroundings and the SWR curve is flat anyway.
5. Position of the antenna at strong winds
At strong winds the antenna should be placed in a way that the tips of the elements show straight into
the wind which means that the boom stands broadside to it.
Hereby physical stress to the full size elements is avoided and their duration is enlarged.
To Next Page