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Re: [Discuss-gnuradio] How to generate a FM signal?

From: nansai hu
Subject: Re: [Discuss-gnuradio] How to generate a FM signal?
Date: Tue, 27 Oct 2009 11:27:04 -0400

I just want to do a demo about two radios in one USRP by time divition, both are FM&FH, but with the intention to distingrish these radios,the FM deviation and FH hop step should be different.Now I could control the hop step,but the FM deviation can't be controled(FM deviation should be12.5K and 25K,which input to  max_dev in WBFM module)

2009/10/26 Josh Blum <address@hidden>

nansai hu wrote:
I appracite you could tell me what is the meaning of following paramaters:
      address@hidden audio_rate: sample rate of audio stream, >= 16k
      address@hidden audio_rate: integer
      address@hidden quad_rate: sample rate of output stream
      address@hidden quad_rate: integer

This is the input and output rates of the block.

      address@hidden tau: preemphasis time constant (default 75e-6)
      address@hidden tau: float
      address@hidden max_dev: maximum deviation in Hz (default 75e3)
      address@hidden max_dev: float

No idea, check the source, but the default values are good to get a working wbfm radio.

I try to change the max_dev from 10 to 1000,and give it to a usrp source as
baseband signal,

For transmit, the usrp expects numbers between +/- 2**15. Your transmit amplitude should be on the order of 10k. What are you sending it?


but, the bandwith on spectrum analyize don not change.How to change
deviation of a fm signal?

2009/10/26 nansai hu <address@hidden>

I tried to run your code wfm, but there is nothing happened in my spectrum
I am just wondering that your code is in baseband or how to add a carrier
freq by usrp source.

2009/10/24 Josh Blum <address@hidden>

nansai hu wrote:

Is anybody had a experiment about How to generate a FM signal?

Use the wideband and/or narrowband fm blocks; just specify your data


or tell me how to use FM MOD or VCO module in GRC, what is the paramater
sensitive means?

check the source :-)


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