The Quartzmite V1.0 SMT QRPp
CW transceiver

The prototype was built and tested. With a 9v supply it is delivering about 0.25 watts and with a 12v supply about 0.4 watts. With the 12v supply on Rx it draws about 15mA and on Tx about 150mA. Some effort was focused on increasing the power output by adjusting things in the driver and PA part of the circuit to make them more efficient.

One area that took some work was the 'shift' function that moves the local oscillator between two frequencies about 700Hz apart, this is used to separate the Rx and Tx frequencies. The original Rockmite design is rather basic in this area and it has proved impossible to get a sensible shift with any of the available zener diodes. After some experiments I decided that rather than use a single zener diode to generate a reference voltage and use ground (0v) for the other voltage, it was better to use two zeners with the lower voltage one switched by the FET. To do this on the prototype board I cut the track going to the drain of Q2 and inserted D7 between there and R10 where it just fits. As well as making it easier to get the required shift this has the additional benifit of allowing the use of the low end of the varicap capacitance range, which means we are pulling the crystal less and so the oscillator is more stable.

The output waveform on a 'scope is a nice sine wave and my spectrum analyser measured the transmitter 2nd harmonic at -52dB so the low pass filter is performing as expected.

The last thing to do was to put it in an enclosure, I had a 2oz tobacco tin at the ready since the prototype board was (by design) slightly too big for an 'Altoids' tin.

the prototype in it's tin
The prototype installed in it's tobacco tin.

A schematic is available here, a Bill of Materials here, and a set of construction notes here.

The Quartzmite keyer is functionally identical to Dave Benson's original Rockmite keyer.
A quick push of the control button reverses the Tx/Rx frequency shift.
If a straight key with a mono plug is connected at power up then the iambic keyer is disabled and the rig operates in straight key mode.
With paddles connected, pressing and holding the control button enters speed change mode where one paddle increases the speed and the other reduces it.

The version 1.0 pcb had a few bugs:

the prototype
The prototype during testing.

the bodge for the varicap
The slight bodge required to fit D5, the varicap diode.

prototype PCB
The prototype V1.0 PCB.

PCB image from kicad
The prototype V1.0 PCB layout.

3D View of board
A 3-D view of the V1.0 PCB design.

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