Changes to POWDER indoor over-the-air (OTA) lab

[Kirk Webb]

Hello POWDER community,

We're pleased to announce that we've upgraded the RF/antenna
connectivity in the POWDER indoor OTA lab, and are adding clock
synchronization. The following updates have been done:

* All B210+NUC devices now have 2x2 MIMO antenna connectivity

`ota-nuc1`, `ota-nuc2`, `ota-nuc3`, and `ota-nuc4` are now each
connected to a 4-port antenna (Taoglas MA963), meaning the TX/RX and
RX2 ports on both Channel A and Channel B are connected to an antenna
element. B210 Port to antenna port connectivity is as follows: Channel
A TX/RX to port 1; Channel A RX2 to port 2; Channel B RX2 to port 3;
Channel B TX/RX to port 4.

MA963 datasheet: https://www.taoglas.com/datasheets/MA963.A.BIVW.002.pdf

* Two (out of four) X310 radios now have 2x2 MIMO antenna connectivity

`ota-x310-2` and `ota-x310-3` each have a Taoglas GSA.8841 I-bar
antenna connected to each of their Channel 0, and Channel 1 TX/RX and
RX2 ports. `ota-x310-1` and `ota-x310-4` continue with their existing
antenna setup with an I-bar antenna connected to the TX/RX and RX2
ports of channel 0 only.

GSA.8841 datasheet: https://cdn.taoglas.com/datasheets/GSA.8841.A.105111.pdf

* External clock sources

All radios (X310s and B210s) now have their 1 PPS and 10 MHz clock
inputs connected to NI/Ettus Octoclock devices. Currently the X310
devices connect to one octoclock, and the B210 devices connect to
another; we are awaiting cabling to connect (and thus synchronize) the
two octoclock devices, and will update on the list once this is in
place. This means that currently the X310 and B210 devices do not
share the same external clock references.

NOTE: To use this synchronization, you MUST select the "external" PPS
and/or 10 MHz clock in your radio application.

We also plan to add documentation about the lab and its layout to the
POWDER manual, so stay tuned for that. And please follow-up if you
have questions or issues with the new set up.

Best Regards,
Kirk Webb on behalf of the POWDER Team