I'm calculating the link budget for a rocket communication that reaches 3km altitude.
I'm using HopeRF RFM98W for both ends of the system.
- Max RF output: 20dBm
- Antenna Gain: 3dBi
- 3km FSPL at 433MHz: 94,72dB
After the receiver antenna gain we get: 20+3-94,72+3 = -68,72dBm
The RFM98W has a receiver sensitivity of -148dBm. We calculate the link margin:
-68,72-(-148) = 79,28
The link margin seems a little off. In the examples I saw, they get a link margin of around 8dB, and for another RF module I got a link margin of 29,49 dB which seems normal. This module couldn't sometimes connect in a clear line of sight at 500m so I'm curious how I can get a link margin this big.
I think I'm missing the cable RF loss here. I have used this module with an adapter board now I'm switching to custom PCB. I couldn't find any datasheets for the adapter board itself. I would like to calculate cable rf loss due to a 2mm wide 10mm long 0.5mm thick copper wire on a PCB.