rusty99
Newbie level 1
FSK optimal Deviation
Hi its been a while since i have done this much RF work..
Here is my problem,
i have a FSk transmitter on the 433 ISM band transmitting at +17 dbm with a datarate of 2.4kps. Using a 1.5ppm Tcxo for frequency acuracy.
My Reciver is a narrow band with an AF Bandwidth(-3db) of 4 KHZ, and a sensitivity of -120db SINBAD .
I was using a deviation of +- 3 Khz and while this works ok , i am trying to optimise the range of this link. I have been told that this shouldnt work as my theoretical bandwidth is 8.4khz yet the reciver is only 4khz.
Though the way i understood the theoretical calaculations ( i had to look that one up - quite confussing) was 2(bitrate + Deviation) = 10.8 khz..
so here is the question what is an optimal deviation ? what is the problem if the deviation becomes to small? I can live with 1.2kbs datarate but should i then have a deviation of 1 khz i.e a theoretical bandwidth of 4.4khz or am i missing something all together??
Hi its been a while since i have done this much RF work..
Here is my problem,
i have a FSk transmitter on the 433 ISM band transmitting at +17 dbm with a datarate of 2.4kps. Using a 1.5ppm Tcxo for frequency acuracy.
My Reciver is a narrow band with an AF Bandwidth(-3db) of 4 KHZ, and a sensitivity of -120db SINBAD .
I was using a deviation of +- 3 Khz and while this works ok , i am trying to optimise the range of this link. I have been told that this shouldnt work as my theoretical bandwidth is 8.4khz yet the reciver is only 4khz.
Though the way i understood the theoretical calaculations ( i had to look that one up - quite confussing) was 2(bitrate + Deviation) = 10.8 khz..
so here is the question what is an optimal deviation ? what is the problem if the deviation becomes to small? I can live with 1.2kbs datarate but should i then have a deviation of 1 khz i.e a theoretical bandwidth of 4.4khz or am i missing something all together??