05 December 2011

TX-only transverter for 4m - with mixer

The picture shows my TX-only transverter with the diode ring mixer (SBL-1 or ADE-1) component added. The circuit has not grown a lot, but it does indeed work.

The canned oscillator is now terminated in a 1kohm trimmer and feeds the IF port of the mixer. RF from the HF transmitter goes to the LO port. Trimmers will most probably be replaced with fixed resistors.

As a signal generator I used the FT-817 at 24.9 MHz. Listening on a panoramic receiver I could clearly hear LO-HF (20 MHz) and LO+HF (69.8 MHz). The frequency counter on the mixer output picked up the LO-HF difference, which was expected since there is no bandpass filtering afterwards.

I tried swapping HF and LO signals but the result was the same. Signal output decreases if the HF trimmer reduces the mixer drive.

Next step is to build a resonating termination followed by an amplifying buffer. G3XBM circuit calls for a BF199, which is already sitting on the workbench, committed to take part into this project.