On 12/23/13 5:53 AM, Pete Smith N4ZR wrote:
It's a little hard to tell from the info provided, but if it is to
switch a K8UR array then I think it is ridiculous overkill. Modeling
and actual experience show very little improvement from a 4-element
dipole array over a 3-element one.
True for gain.
One potential advantage is that with 4 elements, you have more possible
directions to put a null, with a simple switching network. Both 3 and 4
element arrays will have a really broad main lobe, so there's no real
advantage to pointing in 3,4,6,8 directions from a forward gain
standpoint. But from a "put the null on the interfering station"
standpoint, having more choices might work better.
These days, though, I think that the direction to head would be to have
1 transmitting element that is optimized for efficiency and max ERP.
And then an array of at least 3 smaller receive elements that you run
into an SDR to do the null forming. The number of elements should be at
least one more than the number of nulls you want.
Minimum "stuff" out in the outdoors where it can break.
And, inherently wide band (the receive antennas can be non-resonant)
Maybe a simple transmit array, but for small numbers of elements close
to the ground, you're unlikely to get more than 4 or 5 dB, and I'm not
sure that there's not somewhere else to spend your time/money/complexity
to get a bigger radiated signal in the desired direction. (like going
to H pol instead of V pol). A lot would depend on the site, too.
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