Didier Juges said the following on 10/28/2006 12:18 AM: > The clock shaper uses a commercial 10.7 MHz IF transformer, readjusted > down to 10 MHz (see schematic at > http://www.ko4bb.com/ham_radio/Manuals/2_GPS_Stuff/Clock_Shaper.jpg). > It provides light loading to the OCXO through the 390 ohm resistor, yet > provides about 2V p-p to the comparator, to get it out of the noise. I > do not know the temperature stability of the transformer, or the loaded > Q, I will check that later. I realize this is probably not an optimum > design, but it's what I could do with what I have on hand. I am not > using the fine tooth comb and tweezers yet, I am still with the rake and > the fork lift :-)
To minimize jitter and tempco, you probably ought to stay away from a comparator if you can. I've had good success using the input circuit from Brooks Shera's GPSDO which is a 74HC4046 PLL, but using only the input circuit and not the PLL section itself. Alternatively, you might get away with a simple capacitor followed by 50/50 voltage divider to provide 1/2 Vcc bias going to the input of the divider chip. John _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
