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How would one use a ProgRock2 in a Colpitts crystal oscillator? A crystal is essentially an LC circuit, while the ProgRock outputs a square wave. Can the ProgRock2 simply replace the crystal? If so, will the Colpitts circuit turn it into a sine wave?

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Does the ProgRock2 start up at the last frequency used before its last power down?

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Steve, N9SZ

Hi
Frequencies which you select
73 DE muhsin TA1MHS

Steve,

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The ProgRock2 is a tiny square wave generator (Si5351a) -- it replaces the entire oscillator circuit -- you don't use it in a Colpitts oscillator, you replace the oscillator with the ProgRock2.? The ProgRock2 has three outputs, each with eight selectable frequencies (banks 0 thru 7).? By default, bank 0 is output, so if you only need one frequency, there's no need for switching.? The switching involves a logic pattern of grounding three select pins.? What I do is use a diode matrix and transistors to present grounds to those selection pads in the correct sequence.? The ProgRock2 needs a stable voltage source for operations -- I use a LM7805 voltage regulator and give it a clean 5 volts.??

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The square wave is usually not an issue, but of course it depends on your application and the circuit involved.

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I've attached a couple of photos that show how I implement the ProgRock2 in a Heathkit HX-1681 transmitter.? It replaces the entire oscillator section on the HFO/Mixer board, and the frequency output is selected by a voltage coming from the band switch.? The output of the ProgRock2 is buffered by a 74ACT08, which was recommended by Hans.

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If you want to know more, I've written extensively about how to implement the ProgRock2 in both ER Magazine and Spectrum Monitor. ?The ProgRock2 is a nifty way to get around the problem of flaky/drifted crystals.

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73 - Steve, KW4H

Tucson, AZ

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Hi Steve,

If you look in the Kenwood Hybrids, Kenwood TS-940, or Icom Classic fora, you may find where I've posted circuits for replacing a reference oscillator with a TCXO.? You can use the ProgRock2 instead of the TCXO.? Another approach is to couple the ProgRock2's output into the crystal oscillator's base, gate, or grid, causing it to lock to the ProgRock2's frequency.? Just a few pF capacitance is usually enough.? With the ProgRock2 unpowered, adjust the crystal oscillator's trimmer so that it's close to the ProgRock2's output frequency.? When you turn the ProgRock2 on, it should lock to it.? This should eliminate the concern about the waveform.? But usually the circuit you're feeding from the crystal oscillator will filter out the harmonics.? Can you be more specific about the Colpitts oscillator you're working with?

Cheers

Halden VE7UTS