Hi Mark,
I suggest installing 3.3-volt Zeners on the GPIO pins connected as outputs to control the radio.? Ashhar Farhan has stated that these are now included in the V2 (and now V3) radios:
/g/BITX20/message/101206You can check out the V2 schematic.
I have done this mod on my DE and installed a 5-volt regulator before each of the 3.3-volt regulators.? Of course, this was after blowing circuits due to the AMS1117 blow-through failure mode.
The most recent addition I have planned is to add TVS protection on the gates of the IRFZ24N.? These have now been installed in the V3 (at least the one I received yesterday).? The TVS is from the Gate to the source.??Here is the part from Digikey:
Mouser also carries it at the same price.? The update is not shown on the V3 schematic.
There is a SWR/PWR sensor mod that some have done.? If you do that mod, I suggest you modify the code for the LPF filter relay selections.? If the sensor is installed, the code thinks you have a v2 or later.? It uses the LPF PIN diodes to solve an isolation issue (I forget why).? This code will clatter the LPF relays on a DE when sending CW.
I do not have the link for the SWR sensor mod saved.? Let us know if you want to add the sensor, and I will hunt for it.
The DE works significantly better with the V3 software.? You must modify the TR transition code if you install the SWR sensor.
73
Evan
AC9TU
