FM frequency test.

Jul 22, 2006 2 Replies
B

Hi All,



I have some FM frequency test questions, could you please advice?


  1. SNR, should I get the definition of SNR first? or we do have general SNR definition for FM ? In my experiance, I will calculate as this:

Major tone power - the most high noise power between BW.


  1. Frequency variation:

A: When FM TX power on, but no music is loaded, compare to when music is loaded. B: When FM TX power on, compare RDS transmitting data and no data.



I am not quite understand the RDS operation, seems a second FM TX near major tone...?


  1. I saw the major tone (FM freq,ex: 100MHz ), when music is loaded, the whole frequency variation is very big, almost become a triangle ( originally is a single tone ), is that correct?




Thank you very much!



Best regards, Boki.



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V

Signal to Noise Ration is defined as the difference between the carrier and the noise floor, measured in dB. There are also some variations of the SNR as:

- Spurious Free Dynamic Range which is the lowest difference between the carrier and the adjacent subcarriers or images

- the phase noise( dBc) which is measured at a standardised distance (

1Khz, 10KHz, 100Khz or 1Mhz) from the carrier and it caracteristic to the oscilation source

That's depends on the resolution and bandwidth you've set on your spectrum analyzer.

greetings, Vasile

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A

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