The Project
The following outlines how I established a portable GPS Disciplined Oscillator for use with my microwave Transverters. The unit is based on the Trimble Thunderbolt and the object of the Project was to allow the “Thunderbolt” to be used in the field as well as in the radio shack.
Prior to commencing the project I reviewed as many articles as I could find on the internet as I was not looking to reinvent the wheel. While there are many excellent ideas appearing in the articles I could not find an article that satisfied my requirements. My needs were quite simple I thought and really centered on a high percentage of usage away from the home QTH.
For portable work there was a need to allow the unit to be operated on 12 volts DC making it compatible with all of the microwave transverters and other portable equipment used by me for field days and portable style operation. In addition there was a need to make the change over process from AC to DC as simple one and ensuring that the unit would also be polarity protected.
“Those of you who have operated portable will know how easy it is, even for the most experienced operator, to make a mistake, in the haste of the moment, when setting up a portable station, to reverse the supply polarity and without polarity protection the ultimate failure occurs! The result equipment destroyed.” The challenge, in fulfilling these requirements, was to make sure that the solution adopted was cost effective. By the way the total cost of my project was under $200 and has resulted in a very functional and flexible piece of equipment.
In developing this project I was determined to use readily available components and to make the unit as light as possible while allowing it to be robust to allow it to survive Field Day activities.

Front panel
Back panel
This image shows the inside of the unit.

An explanation of the Project will follow shortly.

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4 Responses to GPSDO

  1. David VK4DC says:

    Congrats on a beautifully finished home brew well done hope i can get there too David

    • vk4zq says:

      Hello David,
      Thank you for your kind words. I have had a great time developing the projects.
      The resulting performance have been very pleasing. It’s great when it all comes together!
      Regards Roy O’Malley VK4ZQ

  2. Bruce says:

    G’day Roy
    An absolutely excellent blog and set of photos. It is a fine example for all Amateurs of what can be done if one puts one’s mind to it.
    The only problem that I can see, and where you may have trouble in the future, is your use of one of those rectangular power switches in your GPSDO. Having worked in the electronics trade for a long time, I have seen many of those switches fail… usually because there is not enough downward pressure on the contacts to start with, slight intermittent making of the contacts, the contacts become heated and the plastic case becomes deformed, causing the switch to fail.
    This is especially so with power supplies, when there is a sudden inrush of current to charge capacitors.
    Keep up the good work. I wish that I had a workshop to be able to do the same.
    73… Bruce… VK2EM

    • vk4zq says:

      Hello Bruce,
      Thank you for your email and the kind words. Thank you for the advice on the switch type. I will certainly keep a watchful eye on it in the future.
      Our hobby certainly has had a checked history but I must admit I enjoy the Microwave world with its twists and turns and ample scope for experimentation.
      Thank you again for your comments!
      Regards Roy VK4ZQ

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