The GM0UHC Brand Image! /cont
The completed lower deck
I was in two minds as to whether two independent PSUs were required for the two PAs or if a single PSU would suffice. I believe the answer to that one is a definite on the 2 PSUs! The PSU in my original transverter was completely solid state . . . i.e. ALL the switching was done with MOSFETs. However, even the beefiest MOSFETS incur IR losses. This time round I opted for a pair of high current relays to switch the bulk of the current. A small oversight on my part resulted in the +12V supplies NOT being isolated from each other. When testing the completed transverter, one of the PAs oscillated . . . but only when both were powered. There is a reference on GM4ISM’s website which suggests that for maximum stability, at no time should the +12V line exceed +13.7V. Since this is the bulk DC input, it is set at +13.8V in my case. Mark goes on to suggest that a maximum of +12.5V for this line is probably what to aim for. SO I knocked up a little plate with a couple of 7812 regulators on it and both Pas behave themselves now.