Hi gang
Did the 'subject' of this message get your attention? Well, this is the
latest antenna project at VK6VZ.
In a bid to get a bigger signal into the northern hemisphere during the nh
winter, in the next few weeks I am going to suspend a yagi-type parasitic
reflector behind the inverted vee dipole here. While the inverted vee
(driven element) is up around 90' high at the apex, the reflector will be
lower, in an inverted-U shape (66'-plus of wire up semi-vertically, 132' of
wire horizontally and 66'-plus wire down), with the horizontal span around
50' to 55' high.
The centre of the reflector will be 65'-plus from the apex of the inverted
vee (from point to point), but the ends of the antennas will probably be
somewhat closer than this - about 35 - 40' I'd guess. I thought I would
start with a reflector about 5% larger than a conventional half wave antenna.
My intention is to place a 12V relay in the centre of the reflector, so I
can open circuit the reflector (ie. split the reflector in half to detune
it) and return to the relatively omni-directional pattern of the inverted
vee.
The antenna would fire north (the only direction available!) up towards the
grey line, to take advantage of sunrise and sunset openings.
I would be fascinated to hear from anyone who has tried an antenna like
this, or has any ideas about implementing it better than I mentioned above
(particularly with regard to detuning the reflector). Grounding the
reflector effectively is hard here, as the soil conductivity is so poor.
I am a bit concerned about how much the reflector will drop the impedance
of the inverted vee and give me a mismatch when using it as the driven
element of a 2-element array.
Vy 73,
Steve, VK6VZ
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