# Need help understanding RF radio parameters

I am experimenting with the SPSGRF-915 RF transceiver, particularly with the different center frequencies.

My question mainly revolves around the situation where multiple devices can transmit at the exact same time, and I need to make it possible for the respective receivers to decode the signals properly.

I plan to achieve this by modifying the center frequencies of each transmitter and receiver setup/pair so that each setup/pair can decode these signals properly.

If I were to configure transmitter A (TxA) and receiver A (RxA) to:

• Center Frequency: 913MHz
• Channel Space: 100kHz
• Bandwidth: 160kHz

and transmitter B (TxB) and receiver B (RxB) to:

• Center Frequency: 915MHz
• Channel Space: 100kHz
• Bandwidth: 160kHz

Would it be correct that these two setups should not interfere with each other because of the different frequencies and the bandwidth?

In the example above, since the bandwidth is 160kHz, would that mean that TxA would most likely occupy the 912.92 MHz to 913.08 MHz range, and this would not interfere with TxB because TxB would most likely occupy the 914.92MHz to 915.08MHz range?

What are other scenarios that could cause the setup above to fail?

Can a high transmit power (say +15dBm) on either transmitter cause the other setup to fail?

• What is the characteristic of the filter that establishes the 160 kHz bandwidth? All filters allow some energy/signal through outside of their specified cutoff frequencies. Mar 24, 2021 at 0:33
• @SteveSh The bandwidth of 160kHz is configured through software, but that bandwidth value itself was derived from the datarate. I'm not entirely sure, but I believe the bandwidth determines the frequency range that can be decoded by the receiver? Mar 24, 2021 at 1:07
• As you increase the TX power, there will be more energy at the edges of the frequency mask. How much depends on how the system controls the bandwidth. Mar 24, 2021 at 1:07
• @SteveSh I should also add that the frequency deviation is 40kHz. I think this parameter is the parameter that determines the channel width? Mar 24, 2021 at 1:07
• The American 915MHz band is tricky, because it has lots of rules about how you are allowed to send, regulated by something called FCC part 15. Simplified, this band requires that you jump around between a bunch of different frequencies according to a random sequence, never to return to a used channel before a lot of time has passed. Pre-made radios for this band typically features these things. Or alternatively, you can stay on one channel but reduce your output power dramatically, somewhere down to ~0.75mW ERP. For these reasons, your question doesn't make much sense. Mar 26, 2021 at 10:55