<<<<In order to detune the elements to allow omnidirectional radiation from
the vertical, authors suggested to ground the elements where they are
switched from director to reflector which will give you aprox 74.5 mts long
element grounded at the base.>>>>>
You better have a good HV relay for that!
<<<<
In my case I have a relay installed at the corner of the elements which when
opened leave only 53.6 mts sloping in the space from the top of the 1/4 wave
tower to 40 mts from the base and 3 mts from ground. My question is, could
it be possible instead of grounding it or leaving it opened, to add an
inductor or a capacitor at that 53.6 mts point in series with the remaining
element (24.0 mts for the reflector and 17.6 mts for the director) in order
to make them invisible to the tower?>>
The relay requirements are much more reasonable at the point you are
switching. With 1500 watts you have about 600 volts peak across the relay
contacts and no significant pattern distortion. It is much better than the
other method for everything, and requires no detuning capacitor or inductor.
It has to be a good relay with good insulation.
My model shows the array slightly out of tune with those dimensions. The
director is slightly low in current. But it has good F/B.
_________________
Topband Reflector
|