A larger antenna mounted as high as possible is your best bet. We offer these antennas that work well but are large.

How can I connect these antennas to the RTK Facet using what cable

The cable included with the RTK Facet is designed to directly plug and play with these radios (or the telemetry radios).

what distance can be obtained

Depends on your surroundings. These will not transmit through hills or large natural objects (aka rocks). Buildings, etc degrade the distance. In general open air, you can get a few miles. In an urban setting, it's a few blocks.

what is the difference between serial lora and the teletry radio

The LoRaSerial is built for maximum range, where as the telemetry radios are optimized for greater data bandwidth.

Dozens, perhaps hundreds. I've had 32 operating simultaneously without a noticeable degradation but they were all transmitting dozes of bytes, not hundreds (ie not full bandwidth). It depends on how the radios are configured and how much data is being pushed through them. Very few use cases require 100% of the bandwidth of the system so this allows collisions and re-transmissions. If say two un-paired/un-known radios happen to transmit on the same frequency, likely that 400ms portion of the packet will become corrupt. The receiving radio(s) will note the corruption and fail to transmit an ACK. The transmitter will then re-transmit the packet at which time it will have moved significantly through its hop table moving to channels that are open and available to get the packet through.

Now say you have 50 pairs of radios all transmitting at 100% bandwidth. No doubt it will be very hard to get data through, but you can do things like reduce your min/max freq by half a channel to force all the freq in the hop table to be 1/4 of a channel away from the 50 blasting radios. My math is likely wrong here, but the point is that you can slice and dice the 902 to 928MHz spectrum in a multitude of ways to allow a number of radios to coexist.

Check that the baud rate set in the radio matches the baud rate of your sketch. A discrepancy will cause this sort of behavior. The default for the radios is 57600 bps.

Yes they are.

The included cable plugs into the UART connector. An Arduino or ESP32 can then send and receive data to the radio.

I may be confused, but two UART cables are included. The UART connector pinout can be seen both on the sticker on the outside of the enclosure and the PCB silkscreen seen here.

The pinout is as follows:

• PWR - 3.3-5V
• RX - Receive (Input into LoRaSerial)
• TX - Transmit (Output from LoRaSerial)
• CTS - Clear To Send (Input into LoRaSerial)
• RTS - Ready To Send (Output from LoRaSerial)
• GND - Ground

It's here under the Hardware Overview. The average standby current at 30db transmit power is ~60mA. It depends on how much data you're sending. Assuming ~20 bytes, at airspeed 4800, this is 480 bytes per sec, or about 20ms of transmit time. Let's round up to a second because there's ACKs and possible retransmits. For 59 seconds you'll be at ~60mA. For 1 second you'll be at 510mA, or an average of 67.5mA. Using a 2000mAhr battery, you'll get 2000 / 67.5 = ~30 hours. I presume from here you can calculate your solar and batt needs.

That is the million dollar question and nearly impossible to answer without actually setting up the radios at your location. In short, in an urban area, 1000s of feet (more than 0.3km) but likely less than a mile. But there are many factors that will improve the range:

• Mounting the antennas high - the higher you can get away from the ground and obstructions, the better. The SparkFun antennas is on top our building. I know not everyone can do this, but laying the antenna on the ground, or behind brick walls, or near metal studs or pipes, makes things worse.
• Avoid the earth. Getting RF through buildings is hard. Getting RF through hills or mountains is a show stopper.
• Turn down the airspeed. By default the radios are setup for airspeed 4800 which is ~400 bytes per second. For every halving of the airspeed, you effectively double your range. I.e., 2400 is twice as far as 4800, 1200 is twice as far as 2400, etc. Note: This increases your power budget because you are transmitted for twice the amount of time.
• Get a larger, directional antenna. Again, not everyone can mount a big antenna on the top of their house, but you rarely see small antennas on city RF infrastructure. The kit comes with good 1/2 wave 2dBi antennas. You'll need high gain antennas and potentially directional antenna (such as a Yagi) to maximize RF transmission and reception.

Hope this helps!

Good question: it's CAB-18079 but please do note that the wire colors may very.