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
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
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@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
Hi Francesco and all,
If you do it the simple way, that is use the signal as is like is done in the Funcube you can not use a balun transformer. Going from DC to 48 or 96 kHz is not possible. Audio transformers can not provide that bandwidth. It is possible to go from perhaps 5 to 96 kHz in a transformer, but highly impractical because of the heavy magnetic shielding that would be required.
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@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@hacklabproject.org
Hi 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@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@hacklabproject.org
Hi Zilvinas,
There are many OP-amps that you can choose from. The dynamic range of the E4000 is good, but not super-high so you do not need something expensive. (The WSE system is ultra-high performance, but today old.)
Have a look at what they use in Softrock and other soundcard based hardware. You should be able to find something very cheap for a single 5V supply.
I am not up-dated on what is available, but first I suggest you have a look in your junk-box:-)
A poor OP-amp could cause an increased noise floor. That can easily be checked by connecting the two resistors to the same output pin of the E4000. If the noise does not go down significantly, OP-amp noise is too high.
A poor OP-amp could also cause distortion. Typically a signal twice as far from the center as a strong signal. There could also be intermodulation.
Dynamic range performance will be much better than for the Funcube because there is not a LNA in front of the E4000. With appropriate isolation from USB and computer noise you should get the same NF as possible with the Funcube.
Regards
Leif / SM5BSZ
Hi 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@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@hacklabproject.org
Yes! Tap. The only problem is a sound card can only accommodate 48K - 96K bandwidth, some maybe as wide as 192K. The noise at the center of tuning may wipe out much of this tuning. What is needed is a tunable "Zero IF" double-balanced converter like a SA602(612) or NC1496 on the output of the Tuner chip driven by a very clean VC oscillator, these chips have differential I/Q inputs so the tuner can be used as it was designed and not constrained by that funky 8-bit A to D chip. A 16 bit I/Q sound card conversion of the double-balanced IF tuner output would reveal much the slow 8 bit converter does not, like very good noise cancelation, ultra narrow-band RADAR signals, very high speed frequency hopping, and spread spectrum modulation.
I would create such a thing if I were not involved in more profitable ventures.
Jay Salsburg
-----Original Message----- From: osmocom-sdr-bounces@lists.osmocom.org [mailto:osmocom-sdr-bounces@lists.osmocom.org] On Behalf Of Zilvinas, LY2SS Sent: Wednesday, June 12, 2013 3:14 AM To: osmocom-sdr@lists.osmocom.org Subject: e4000 r820t signal output
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
----- No virus found in this message. Checked by AVG - www.avg.com Version: 2013.0.2904 / Virus Database: 3199/6404 - Release Date: 06/12/13
-
Francesco Gugliuzza -
Jay Salsburg -
Leif Asbrink -
Zilvinas, LY2SS