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It’s worth noting that different antennas will have different radiation patterns. Warg commonly uses 3 kinds of linearly-polarized antennas: Monopole, Dipole, and Moxon style antennas. These will all have slightly different radiation patterns, but monopol/dipole antennas are not directional, while a moxon is. Moxons are also linearly polarized, meaning that you want the active element the same direction as the airside antenna.
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Note that all dipole/monopole antennas have deadzones along the AXIS of the antenna (the direction the wire is placed). This means that if an antenna is mounted horizontally (flat), then turning the drone 90 degrees may put you in a null zone.
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The TX16 was set to 250mW max power, dynamic on. The Ranger was originally set to 250mW, dynamic off, but was later changed to 1000mW, dynamic on.
Results
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What we noticed was that the TX16 was constantly at 250mW, with link quality 80-100 in close range operations (< 100m). As the drone moved away, the link quality decreased to 40-60% at 1.1km. TPower never lessened below 250mW. Moving away from airport did not help.
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The drone was placed on the workbench, USB power delivered by the WARG laptop. The ranger and tx16 were placed on the blue bench ~ 1m away, taking measurements for TPower, LQ, and RSSI. This configuration ensured the most free air between the drone and the groundside (no vanny, or other cables in the way - less reflections & alignment issues). The ranger was powered by Hardy Yu’s laptop, while the tx16 was plugged in to charge the low battery (7.2v after test #1). Output power for the tx16 was limited to 10mW , while the ranger was limited to 250mW with dynamic power.
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This improvement is likely due to the fact that there’s lots of Wifi/cell/interference inside E7things in our bay to cause reflections or interactions between other antennas. Notice how we are at a steady 10mW of transmission power now, with 100% LQ.
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All in all though, RTL always worked and we only flew within capabilities of ourselves and the drone 
Flight Test Logs
Hotlinks
Logs (view only - must be signed in to UW account): https://uofwaterloo-my.sharepoint.com/:f:/g/personal/uwarg_uwaterloo_ca/EnmcEWaGxHdEiYuD6xJM7XMB3XnpnPPU6S26vowZ1zjkQQ?e=gwI5j1
Media: (non existent as of rn)
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The graph above is the accumulated MAVLink Packet received/sent in the flight controller (PX6) during a flight test
The red line represents the data sent and the green is the data transmitted
The key takeaway from this graph is that we know the telemetry RX/TX isn’t proportional. The RX:TX has a 10 times ratio difference shown in the graph
The airport uplink/downlink bandwidth ratio is balanced and unchangeable. In the future, if the ELRS airport uplink/downlink bandwidth could be customized, then the telemetry transmission quality could be further optimized.
Hotlinks
Logs (view only - must be signed in to UW account): https://uofwaterloo-my.sharepoint.com/:f:/g/personal/uwarg_uwaterloo_ca/EnmcEWaGxHdEiYuD6xJM7XMB3XnpnPPU6S26vowZ1zjkQQ?e=gwI5j1
Media: (non existent as of rn)
Flight test thread: https://discord.com/channels/776618956638388305/1134564410652885002
Suggestions for future
Here’s some things that we should (probably) do in the future
CRSF instead of SBUS for RC
Using CRSF instead of SBUS means that we can’t use the RCIN port, but instead connect to a serial port (TELEM 1/2/3/4).
This gives us a few advantages, the biggest one being redundant telemetry over RC link. We noticed often that the RC Link was more reliable than the airport link, and having the ability to get telemetry back from ardupilot and running a Yappu script means that if our airport link goes down (more likely than RC), we still have the ability to view telemetry and fly the drone (especially verifying things like correct flight mode - RTL).
True diversity or PA/LNA Equipped RX
A receiver with a PA/LNA will have more telemetry output power (up to 1W), meaning that it’s less likely for airport LQ to degrade (especially since airport is 90% Air → Ground). It is common to run TX modules as RX for airport.
Diversity receivers help protect against null zones and interference that may be caused by the angle/position/rotation of the drone. Highly recommended and not significantly more expensive than existing RX’s.