Frequency Locking and GPS References
Simple GPSDO for LF / VLF Use the 1 PPS output from a GPS module to phase lock a crystal oscillator.
Short term stability is poor, but is well-suited to signalling that will be integrated over periods of tens of seconds, or longer.
VE2ZAZ GPS Derived Frequency Reference - Bertrand Zauhar's PIC Based GPS based 10MHz standard working from the 1 PPS signal. Better short term stability than the simple GPSDO, but ought to be kept running continuously due to long lock-up time. Needs a good high spec ovenned 10MHz VCXO
Short term Stability A comparison of several 10MHz References
Short term stability test on the Leo Bodnar GPSDO
Locking Microwave Local Oscillators
Reflock calculation
10MHz Distribution amp and Frequency Doubler. Taking 5MHz input from a standard frequency source, it generates several 10MHz reference outputs with good interport isolation. This isolation is necessary to prevent interference generated in the logic stages of various items of test equipment from being injected back into the 10MHz distribution system, interfering with other more sensitive users.
The original MSF Locked Frequency reference, Published in RadCom April/May 1994
More on using GPS derived techniques with beacons can be found in Publications
Simple GPS Disciplined Oscillator
Low chip-count design using the 10kHz output from a Jupiter-T GPS module
An even simpler design
First Published in Radio Communication october 2002
Simple frequency locking of local oscillators for microwave transverters using a sampling mixer
Frequency Locking Microwave sources
Generating arbitrary frequencies, accurately
Calculate the nearest R and N divider ratios for locking an oscillator for an integer-PLL synthesizer.
Fout = M * N * Fref / R
Specify wanted output frequency (Fout), RF multiplication (M), reference input frequency (Fref) and the minimum and maximum limits for the comparison freq. It will then go away and find the best values of R and N to minimise the resulting frequency error.
A set of Gerber files for the PCB are here.
Part 1 ,
Part 2 - PDF Files
The Mark 2 version. More stable design with 5 or 10MHz reference output
Full Article
Circuit Diagram GIF file
