Bob (and anyone else into this bullseye at microwave type thing!) Anyone interested I will be around on Teamspeak at 0100 tomorrow night to brainstorm this neat stuff! Forum is "It's about Time"
Eric -----Original Message----- From: Bob Tracy [mailto:[EMAIL PROTECTED] Sent: Sunday, January 01, 2006 11:05 AM To: Eric Ellison; [EMAIL PROTECTED]; FlexRadio@flex-radio.biz Subject: RE: [Flexradio] A question on Frequency stability vs. Temperature Eric et al, Thought this tread might be a good place to post an update on the oscillator project. I assembled the PLL using the card I designed from Joe Ruggieri's (the eBay source) schematic. I got the GPS antenna up and got the Jupiter receiver working. I initially tried to use my Kenwood IC-232 level converter on the Jupiter data interface but that was unsuccessful. I resolved the problem with a very simple circuit using a MAX232. Using some free software (GPS Diagnostic http://www.commlinx.com.au/gps_diag.htm) I verified I was getting good GPS signals. At my location and with the antenna mounted just outside the shack window, I am seeing from 3 to 8 satellites at any given time. Hooking all the various components together appears to produce a well-locked 10 mHz signal. I say "appears" because I have nothing better than WWV and a DVM on the OCXO control line to check the accuracy. Now the bad news. I picked up an external clock kit from Flex and tried to install it in my SDR-1000. First thing I found was that there have been hardware changes that affect how the kit is installed. I don't know precisely when the changes were made but my two year old unit has a PA circuit board connector exactly lined up with and adjacent to the mounting hole for the external clock BNC connector. Gerald said to move it to one of the transverter BNC holes (which is OK but I really plan to install the 2 meter transverter at some point in time). Next, I found that the RG-174 coax furnished with the kit was about an inch too short to reach the new BNC location so I lost another day finding some RG-174. Connecting the SDR-1000 to the external clock resulted in severe signal distortion. The OCXO supplies a 1.7 V P-P sine wave into a 50 ohm load which is within the Flex specification. All the internal jumpers were correctly installed and the software setup was modified as required. Converting the SDR-1000 back to internal oscillator gets rid of the distortion so I'm confident the problem is somewhere in the oscillator control circuit. Today I'm going to go back to square one. I am going to eliminate all the circuitry in the GPSDO and start with just the 10 mHz oscillator to see if I can isolate the source of the distortion. I suspect it is some sort of phase noise coming out to the PLL but I am going to start with just the OCXO driving the SDR-1000 and go from there. My second step will be to decrease some ground lengths and add some better shielding to the 10 mHz and 25 kHz circuit wiring. I'll post my results as they occur. Bob K5KDN -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Eric Ellison Sent: Sunday, January 01, 2006 8:18 AM To: [EMAIL PROTECTED]; FlexRadio@flex-radio.biz Subject: Re: [Flexradio] A question on Frequency stability vs. Temperature Larry The last I heard from Bill - KD5TFD on Teamspeak yesterday, was that his weekend goal was to interface the Xylo to his GPS 1 pps, so he may beat us all! Also I am interested in where he is going to pull the sigs out of the SDR. No body commented on that message, but it it seemed like a better idea than messing with the 200 mhz LO. In the FPGA - SDR iteration, if we can do a long term average of the GPS sigs then we might not even need a stable slaved 10 mhz standard. In any case, I have ordered what I think is a pretty good deal from the guy Bob - K5KDN is working with. He is selling these Oscillators on E-Bay for 75 bux and has a simple kit of parts for slaving to the 10 khz GPS sig. http://cgi.ebay.com/New-Isotemp-10MHz-OCXO-1PPB-EFC-For-GPS-Discipline-12V_W 0QQitemZ5847210309QQcategoryZ48702QQssPageNameZWDVWQQrdZ1QQcmdZViewItem On way or tother this type of circuit and osc is what non-fpga SDR-1000 owners could use for good stability with the existing modification kit from FlexRadio. Brainstorming session on Teamspeak next Wed night at 0100. Eric2 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Saturday, December 31, 2005 11:02 PM To: FlexRadio@flex-radio.biz Subject: [Flexradio] A question on Frequency stability vs. Temperature Xyloonians, Build a selectable output frequency standard referenced to GPS or WWV. M/N type thing. Have its frequency output within the range of the soundcard by looking at but offset from the frequency tuned to at the moment. Maybe have it outside the pan adapter window so it doesn't distract the operator. Or put it in the window with a red X to show it is working. The PowerSDR software measures this frequency and compares it to the Xylo frequency number, and adjusts the SDR display to correct it. This now takes into account all the oscillators in the SDR1000 and the soundcard and is continuously compensating. No need for VCO stabilizing the oscillators. All to You Year of the New Happy! Hardware designed by hardheads Software designed by softheads Larry - K2LT - I design hardware! > From: KD5NWA <[EMAIL PROTECTED]> > > > The project being discussed for the Xylo is; > > 1. Thermal isolation with a accurate heater to reduce the drift. > 2. Use the Xylo to connect to a GPS and have a accurate 1 pps clock > 3. Use the 1 pps clock to measure the DDS 200MHz clock, > integrate multiple reading to make for finer resolution. > 4. Use the 1 pps clock to measure the A/D clock, take multiple > readings also. > 5. Feed the results to the PC who will proceed to correct the > internal math so there is no drift. > > No attempt will be made to change the physical 200 MHz clock to > something else that is changeable, so phase noise is not > affected. The Xylo will measure, the PowerSDR software will use the > data to correct it's internals, resulting in very accurate, and > stable frequencies with minimal changes to the existing hardware > > That is my understanding on what the game plan is. > > _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
