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

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.

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(a)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(a)hacklabproject.org