A forced re-vamp of the 4mTransverter /cont.
My initial thoughts were to scrap the 4m transverter and build a completely new one, but as I poked around inside it appeared that the only casualties were the two relays and the two resistors (and possibly the two transistors). Then it struck me that given the checkered history of decidedly odd relay problems, it was time to re-think the 144MHz-28MHz transverter side of things. (This is a dual-conversion transverter with a 28MHz Intermediate frequency). No gain is required in the receive converter (28MHz to 144MHz) but some gain is required in the transmit path to drive the 28MHz to 70MHz up-converter. To this end, I simply sawed the first two active stages off the old 28MHz PA.
The rear-panel variable capacitor was replaced with a couple of trimmer capacitors (nominally 27pF when set). The output of the small amplifier was measured at about 0.5mW on transmit so the input attenuator in the next stage was adjusted accordingly.
The basis of the revised 144MHz to 28MHz transverter
The re-vamped 4m transverter is now simpler, uses more reliable relays and since the drive into the second converter stage is now only 0.5mW as opposed to 1W, overall current drain is much less. The output is still a good 30W at 70MHz.