How to calculate InterPacketRxDelay?

[Tylerlee12]

Hi all.  I'm writing some code for an RFM69W, using the LowPowerLab library code as a model, and am trying to figure out what the InterPacketRxDelay should be in RegPacketConfig2.  Looking at the documentation for the RFM69W (http://www.hoperf.com/upload/rf/RFM69W-V1.3.pdf), it says this:

After PayloadReady occurred, defines the delay between
FIFO empty and the start of a new RSSI phase for next
packet. Must match the transmitter’s PA ramp-down time.
- Tdelay = 0 if InterpacketRxDelay >= 12
- Tdelay = (2InterpacketRxDelay) / BitRate otherwise

It says it must match the transmitter's PA ramp-down time.  Is that set somewhere?  How do I know what I should be setting here?  Here's the config code in the library: https://github.com/LowPowerLab/RFM69/blob/9000aa379fd15ff9d473baccab3f167e83cfe828/RFM69.cpp#L88

[ChemE]

You can set PA ramp up rate, is the ramp down rate the same perhaps?  I am not aware of any way to set PA ramp down directly.

[perky]

The PA ramp time I think is symmetrical with the ramp down time, at least it makes sense to be so because the reason for it is to stop spectral splatter due to higher sideband content in the transmitted signal when quickly turning on and off a carrier.

Mark.

[Tylerlee12]

Hmm, interesting.  Guess I'll just stick with the library has and hope for the best...