Good morning to all the group subscribers !
Some notes on AM synchronous demodulation modes in Ciao Radio . There are three ways : AMs , LSBs , USBs . In all this modes the carrier is locked from a software PLL in the range +/-25 Hz to avoid low frequency beat or fluctuations due to the fact that the beat is not synchronous with the carrier .Tuning has to be accurate at minimum +/-25 Hz to achieve lock . In AMs both Side Bands are demodulated and superimposed . You use the maxium possible of the power generated from the AM transmitter . But when the two sidebands are not the same due to selective fading or interference the superimposition is not perfect . In this case , is better to use LSBs or USBs choosing the less interfered band . This is what SWL has showed to be the maximum for them while receiving AM broadcasting stations . There is also "normal" AM , that mathematically implements the rectifying process . In this case reception is only minimally affected from the tuning precision ( +/- 1Khz give only minimal differences ), but a rectifying process is not a linear process and you can see distortion coming up in the demodulation filter window outside the mask of the brickwall filter used before the rectifying process . This is perceived during reception as an annoying effect . If you could guarantee a frequency stability of +/-25 Hz , AMs , LSBs , USBs gave much better results than AM . 73-ClaudioRe-I1RFQ -----Messaggio originale----- Da: [email protected] [mailto:[EMAIL PROTECTED] Per conto di Patrick Lindecker Inviato: domenica 27 agosto 2006 2.17 A: [email protected] Oggetto: [Spam] Re: [soft_radio] MULTIDEM 1.0 (USB/LSB/AM demodulator for direct conversion receivers) Hello Dan, >Providing the audio detection resistor and cap are removed from the vacuum tube grid >or transistor base circuit to preserve the RF in the output, needing the i.f. bandwidth >you mention. Yes the goal is to avoid electronic filtering. In the DSB receiver that I did, the bandpass filter "is done" first by the bandwidth of the Operational Amplifier and, moreover, by the antialiasing filter of the sound card (at about 23 KHz). RR for your experimentations...I suppose that you mean QSD (normally "bad CW keying") circuit for "not very professional circuit"? RR for "AM Synchronous": normally it's just the fact to receive AM in USB or in LSB. In Multidem, AM is received as in the analogical way (by rectifying the signal). TKS for the info about CIAO. It is a splendid software. 73 Patrick ----- Original Message ----- From: wavelengths@ <mailto:wavelengths%40netzero.net> netzero.net To: [EMAIL PROTECTED] <mailto:soft_radio%40yahoogroups.com> ups.com Cc: wavelengths@ <mailto:wavelengths%40netzero.net> netzero.net Sent: Saturday, August 26, 2006 9:47 PM Subject: Re: [soft_radio] MULTIDEM 1.0 (USB/LSB/AM demodulator for direct conversion receivers) Patrick This seems like something one can use with a simple regenerative receiver? Providing the audio detection resistor and cap are removed from the vacuum tube grid or transistor base circuit to preserve the RF in the output, needing the i.f. bandwidth you mention. In which case this might lead to folk making some interesting home gifts of the simple receiver sort to give to others along with a software such as yours. I have been experimenting with a digitally stablized VFO for use with 455 kHz i.f. sections and a simple QSD circuit. I'll do some experiments with your software as I go along here. It seems very interesting. My last VFO test circuit seems to hold some promise if given the right scheme in a receiver to work in. A sort of ideal mixing scheme for better stability. Its all beta circuits for now, and sometimes its hard, then you stumble upon something that opens it up. I am also building various QSD circuits to explore and test. Keep us posted on any software designs you come up with in the future! P.S. I found out the one can have software do "AM Synchronous" also as well as "C Quam AM", and this is in the CIAO Radio 1.35 software. AM Sychronous is something interesting for folk who like broadcast stations to listen to. {SDR is capable of allot of radio modes.} You can see this at the below link: note it only works in one mode since it is meant to be registered. I think it is USB, I am exploring a licensed version with all of the modes working. http://www.comsiste <http://www.comsistel.com/Download/CiaoRadio/CIAO%20RADIO%20MULTIMODE%20RECE IVER%20-%20TEST%20SET_file/Upgrade%20CD%20Ciao%20Radio%20ENG%2008-08-2006.zi p> l.com/Download/CiaoRadio/CIAO%20RADIO%20MULTIMODE%20RECEIVER%20-%20TEST%20SE T_file/Upgrade%20CD%20Ciao%20Radio%20ENG%2008-08-2006.zip Dan ka9rza __________________________________________________________ PrivatePhone - FREE telephone number & voicemail. A number so private, you can make it public. http://www.privatep <http://www.privatephone.com> hone.com [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! 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