Replies: 7 comments 2 replies
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In my opinion this is never going to work as it should. No matter what. This is an FM transciever, even AM or SSB demodulation is out of the specs, not documented features, and all of the sudden people want AM or SSB transmittion to work. |
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Got my hands dirty and started to experiment. I modified the app main loop, and when in TX , I call BK4819_GetVoiceAmplitudeOut() which provides the current MIC AF Amplitude. I modulated the BK4819_SetupPowerAmplifier bias value using the above value normalised, and i seem to have a working variable amplitude signal, but on the current carrier frequency. I also muted the TX Audio on the TX preparation routine, in order to avoid FM modulation. In order to be 100% correct I would have to use fast fourier transform to get the frequency of AF, in order to modify the center frequency accordingly, but I think the hardware is not capable for this. I think it could work by enabling BK4819 Register 40 (see register documentation for the above) and try to deviate the carrier accordingly and create a DSB signal cheaply. Lets see where this takes us ! |
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The experimenting is the future for all , this cheap radio is the example . I agree about your perseverance and i like read any improvement or not , on this aspect. |
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You may find a test firmware with my initial results here : Code exists in master branch. |
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Now i'm more perplex after see this video making a contact with LSB -DSB - after on FM on a perfect way , on appreciate when changes to FM how sounds the modulation . I know too that have created the mode CW for transmission too . I'ts incredible with this little chiness. I have no words .I need one quansheng more now , i have the 2 on real use , one more for only test . |
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congratulations for your continuous idea with this firmware |
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Hey sfotis , i tested a bit and it's not bad a all , is good for start testing with others devices and firmwares with SSB/DSB band , will test more on free time , for now just the main contact and all seems on good route. |
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I just read a little the code, and it seems that the power level can be controlled by an 8-bit register. By modifying according to modulation this register when TX'ing under SSB modulation would this be able to produce a suppressed carrier DSB signal ? Could the CPU handle the workload ? Would the RF chip accept such rapid changes in power level (I guess we need maybe few khz for decent voice quality). I did some checks modifying some wav files to 8 bit unsigned PCM and the voice quality was not so bad (in order to check how would voice be sampled using 8 bit amplitude levels). What do you think ?
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