Hi Frank, The quadrature demodulator I am using is the LT5517. (40 Mhz to 900 Mhz) I wasn't looking for any specific FM, I was just scanning around hoping to find anything. Commercial radio stations are more reliable to find.
I have been able to listen to many AM transmissions: 590.3 K Hz 1.1111 M Hz Many from 9.327 M Hz to 10 M Hz. If you are interested, the schematic for the RF board I am using is posted in my folder "AD5JO" at the Files section of the AQRP Yahoo group. The LT 5517 requires an LO of 2X frequency and about 1.5 Vpp or larger. I received free samples of the LT5517. Also, I don't have an audio amplifier before the sound card jack. I found that I could get enough signal using the I+ and Q+ referenced to ground, fed directly to the stereo input of the sound card (The I- and Q- are just floating). I plan to add an op amp with a very low gain, maybe even unity, to take advantage of the I- and Q- signals. I first had connected an op amp with a gain of 250, but the Op Amp would occasionally oscillate. Thanks, Dave -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Frank Sent: Monday, February 20, 2006 5:39 PM To: [email protected] Subject: [soft_radio] Commercial FM David, How did you redesign your quadrature downconverter for commercial FM's bandwidth? Did you put the FM signal on a filter with a slope in the frequency response to get AM and thus fit into the sound card's bandwidth? What do you mean by "much higher frequencies"? Frank >Message: 1 > Date: Sun, 19 Feb 2006 02:25:48 -0000 > From: "David WardenDurkee" <[EMAIL PROTECTED]> >Subject: SD Radio V .99 possible Bug > > My first attempt to tune in anything was to look for standard US broadcast FM. I was not able to demodulate anything. The problem may be that my hardware was actually designed for much higher frequencies. Yahoo! Groups Links 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! Groups is subject to: http://docs.yahoo.com/info/terms/
