A handful of questions about RFD900 configuration. I’m using firmware version 2.3.

How should the term NUM_CHANNELS be set? Is there a disadvantage to always setting this to the maximum value possible? Increased synchronization time perhaps? Increased network capacity?

Any guidelines on setting DUTY_CYCLE? I suppose leaving it at 100% allows for the most flexibility at the risk of a single node consuming all network capacity.

Is NETID effectively a unique channel hopping sequence?

What is the optimal way of configuring radios to support a system consisting of multiple aircraft and at least two groundstations? The aircraft don’t need to act as relays for other aircraft.

For others benefit, here is the response I received from Seppo Saario:

NUM channels should be set to the maximum permissible by the standard, in Australia it is at least 20, USA it is at least 50. The number of channels also depends on the data rate. The datasheet has a table of bandwidth (-20dB points) vs datarate. Each hop needs to be down to -20dB between adjacent channels.

Duty cycle at 100% is what we use - especially in a normal synchronised network, all the nodes have their own timeslots allocated. Duty cycle becomes important in EU systems, where LBT and AFA are required.

NETID determines the hop sequence uniquely…

It is possible to use a subset of the band permissible for each pair of radios, eg. One set uses 902-915, second uses 915-928. Or alternatively, to set the start frequency 1/2 a channelwidth above on one pair, compared to the other, so the center frequencies lie in the gaps on the other pair.[/quote]

FYI: check, if - after setting NUM of channels to 50 - radios will ever reconnect after long transmission break (i. e. power on one radio, wait 10 minutes and then power on another).
IMHO 30 channels is reasonable max.