Does anyone have a design for a home-brew compact 5.6 to 5.8GHz collinear antenna that they could share. I have seen the one on the internet for the Home-brew Compact 6dBi Collinear Antenna 2.4GHz. Just looking for something similar.
Steve KF7WGL
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Home-Brew Compact 6dBi 5.1 to 5.8 Collinear Antenna
Mon, 05/09/2016 - 16:11
#1
Home-Brew Compact 6dBi 5.1 to 5.8 Collinear Antenna
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In both cases the tolerances are so tight that it is hard to produce at home. At 5.8GHz 10% error is just 5mm IIRC.
On top of that dual polarity is even better as it can significantly increase the link quality and speed.
MB
I have also played with some commercial co-linear antennas on the Bullet M5 and M2. They work and we used them this past week for a communications exercise over an area the size of a small college campus.
Just a FYI running two omni's like this isn't a great MIMO setup. You would be better with a cheap sector or NanoStation.
First off the antennas may not share the same radiation pattern because of how they are built and installed when putting a vertical omni on its side you end up with a forward back pattern on that antenna and omni on the vertical.
Secondly and more importantly the isolation between antennas is likely not there, the antennas are so close together that the fields can be interacting.
True MIMO antennas generally have a 20-30db or more isolation between antennas, this is power that is not returning to the transmitters to interfere and more importantly the isolation between the two allows the individual signals to be captured better while rejecting the opposite polarity.
Steve
KF7WGL
It could easily be Cross(X) as they make antennas for this (same as a horizontal and vertical but internally the antennas are electrically rotated 45 degrees off the vertical axis.
I haven't ever seen a dual polarity circular polarized antenna but that doesn't mean it can't be done but would be a speciality item and would be needed on both sides of the link.
Right hand and left hand circular would seem like a great way to get two spacial streams for MIMO. The problem is that when a RHCP signal reflects off of something it becomes LHCP (and vice versa) thereby destroying the isolation between streams. Linear polarized signals (V/H/X) tend to remain linearly polarized even after reflections.