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Zilvinas, LY2SS zilvinas at augma.ltHi and thanks all for the remarks guys! On 2013.06.12 20:45, Leif Asbrink wrote: > A differential amplifier is cheap and efficient and can > repalce an ideal transformer. Something like the output > amplifier in fig 1. here: > http://www.sm5bsz.com/linuxdsp/rxiq/antiali.htm > R124 and R125 would go to the two outputs of > one audio channel. AD797 - (ouch) this one is quite expensive over here: ~26EUR for both I&Q channels. I mean not that expensive one couldn't buy but maybe one could find cheaper solution without degrading overall unit characteristics? I am not specialist in operational amplifiers (just an amateur) and don't know what are criteria for choosing right device in this place. What about kind of instrumentational opamp f.e. INA333 ? (This would cost half of that . Besides they are single power supply) (or even dual ne5532? less than 1EUR but not sure how to avoid dual power supply) Best regards, Zilvinas > > A typical soundcard samples at HF. Maybe 5 MHz or higher. > The soundcard uses digital filters for anti-aliasing > and there is no need to add a good filter. Aliasing > may be caused by signals near the Nyquist frequency > and multiples of it, but very simple filters are needed > to suppress those signals since the Nyquist frequency > is typically several MHz. > > Regards > > Leif > > > >> If the tuner output impedance is known, you could use a balun transformer >> of the right type to convert the signal, and get total galvanic isolation >> as an extra. >> Also, you need a good lowpass filter because the audio cards sample at >> 44100 or 48000 Hz and the lowest tuner output bandwidth is surely > 1 MHz. >> >> >> 2013/6/12 Leif Asbrink <leif at sm5bsz.com> >> >>> Hello Zilvinas, >>> >>> This should work very well:-) >>> >>> The IQ signals are balanced and the proper >>> procedure would be to use a differential >>> amplifier to convert the voltage difference >>> between I+ and I- to a voltage difference between >>> the ground reference and the input of the soundcard. >>> >>> You can try just putting a wire from I+ to >>> the soundcard input. A capacitor in series >>> might be needed. The simple solution might >>> add hum and noise near the center frequency. >>> Such problems are cured with the differential >>> amplifier. >>> >>> Then, do the same for Q:-) >>> >>> Regards >>> >>> Leif / SM5BSZ >>> >>> >>>> Hi all ! >>>> >>>> Please excuse me if this is a bit off topic. >>>> >>>> Is there any sense to tap the IQ signals from e4k or r820t to the >>>> internal or external soundcards. >>>> Is it possible at all (with r820t particularly) ? >>>> >>>> (It could seem like reinventing funcube dongle, bet the >>>> performance/price would be still right) >>>> >>>> Best regards, >>>> >>>> Zilvinas >>>> >>> >> >> -- >> Francesco Gugliuzza >> B.Sc. in Computer Engineering >> HackLabProject.org Administrator >> Linux user #374630 >> Tel (VoIP geographic number): +39 0921440446 >> Tel (Libera il VoIP number): 5125320 >> E-mail: f.gugliuzza at hacklabproject.org