Need your advice on a proposed setup. I currently have a PTMP setutp with an AP made of a RB433AH and a R52HNd card connected to a 16 DBi ,120 deg Horizotally polarized sector antenna on chain 0. I Have chain 1 disabled on the card. The clients are 5Ghz SXTs. I run NV2 between the AP and CPEs. This set up works. I have a spare 16 DBi, 120 deg verically Polarized antenna. Do you think that there would any increase in throughput/performance if I were to connect the vertically polarized antenna to the AP and enable chain 1 on AP and CPEs. If yes, what should be the spacing between the antennas? Would this be considered dual polarity? TIA.
Also which of the antennas would go top, the Vertical or Horizontal polarized? The idea would be to connect the Horizontally polarized antenna to Chain 0 and the Vertically polarized to Chain 1.
If one antenna has horizontal polarization and the other one has vertical polarization, then this would be dual polarization setup when using both antennae.
The inter-antenna distance doesn’t matter when polarization is orthogonal.
In fact antennae used in comercial mobile networks are mostly X-polarized (i.e. ± 45 degrees polarization, not vertical and horizontal) and antenna elements used for both polarizations are crossing each other at the right angle (not touching each other of course) at elements’ centres … effectively the distance between both “antennae” in dual-polarization setup in this case is 0.
As to which antenna should be mounted higher: horizontally polarized RF signals are attenuated slightly more than vertically polarized … it has to do with the reflections off the (mostly) horizontal ground. So I’d mount the horizontally polarized antenna higher on the mast.
Thanks for your response. Do you think I will see an improvement in throughput/performance of system, or even an increase in signal levels to/from CPEs?
That highly depends on the CPEs and environment configuration between AP and CPEs. Improvement in signal strength can be anything between zero (with single-pol clients already perfectly aligned to existing polarization, I should hope most clients are in this category) to huge improvement (if existing client antenna is completely misaligned according to polarization).
For dual-pol clients the signal strength improvement will likely be 3 dB (or zero, depends on how signal strength measurements are done in WiFi).
The numbers (0 and 3 dB) in explanations above are true only if adding another Tx antenna won’t affect Tx power of existing antenna (due to country EIRP regulations). If currently AP is transmitting at maximum allowed power, then after adding second antenna single antenna Tx power will drop to half of current power and that might show as -3 dB signal drop (specially for single-pol clients).
Throughput mostly follows signal strength in the range of “fair” to good values. For example: if currently a dual-pol client receives signal from AP at -70 dBm and manages certain throughput, by adding additional antenna signal strength might rise to -67 dBm (or it can remain at -70 dBm, I’m not sure how signal strength is measured in WiFi) and throughput may double. However in bad conditions adding second Tx antenna on AP might mean no improvement for client … MIMO can only work in decent radio conditions, in bad conditions receiver is not capable of decoding both data streams (sent over separate polarizations) and in such case MIMO presents itself as increased noise and therefore transmitter reverts to sending single data stream over both Tx chains.
Even if AP transmits at regulated max power and adding second Tx antenna means reduction of Tx power per chain, clients in good radio conditions (e.g. with Rx signal higher than -60 dBm … and don’t take this number as granted, it’s just my estimation and depends very much on quality of receivers receiver), throughput will almost double anyway … single chain performance stays at maximum in some range of Rx power levels while second chain brings in un-corelated data path.