Ham Radio

One of my projects – GPSDO

For more than a year I have been accumulating parts to build a GPS disciplined 10 Mhz frequency standard. The goal of that is to have a high quality frequency source that I can pump into my oscilloscope, frequency counter and various other gizmos.

I have been thinking about this type of project for a long time. When I lived in Colorado I had tried to get WWV 10Mhz off of groundwave from their site north of Ft. Collins. My electronics skills were not up to the task.

This most recent effort is nearly complete. A year ago I bought a Trimble Resolution-T GPS card from a guy at the Jackson, MS hamfest. I also bought an old HP counter which had their high stability ovenized crystal oscillator off of e-bay (cheaper than buying just the oscillator!). I built a controller board which I purchased from VE2ZAZ (a ham in Canada), purchased the parts and got that all ready. The only hold up now is building power supplies for +24, +12 +5 +3 and -5 volts. I have the parts for all but the -5. Somehow I just have not gotten that done. I have an enclosure.

Why is it so hard to get that last little bit completed?

You may be asking, “What is a GPS disciplined oscillator?” GPS receivers get timing data from the GPS satellites. Certain kinds of GPS receivers are made to then put out a 1 pps (pulse per second) timing signal. Taking that 1 pps signal and a stable crystal oscillator, you “discipline” the crystal oscillator by doing a long term count of oscillator transitions over a hundred or a thousand seconds and adjust the crystal oscillator using its built in voltage control pins. When it is working and locked to the GPS, such an oscillator can produce a steady signal for use as a laboratory standard. The VE2ZAZ controller board uses a PIC microcontroller to manage the integration of the GPS and oscillator, and it has a handful of output ports for connection to lab devices.