I've worked up an FET switching circuit for more reliable CW keying using a hand key or bug with the uBITX. I added a couple of identical stages to handle the dot/dash inputs from paddles as well.
Due to the way the ADC was used for CW keying, contact resistance (varies with the key, length of connecting cable & how dirty the contacts are) was causing random dots & dashes even with a hand key and it was next to impossible to use my bug with it.
The 2N7000 switching stages I came up with give very reliable, low resistance closures to ground on the key line or the dot/dash paddle inputs (through the respective 2.2K and 10K resistors) which makes things work a lot better. I am actually able to key the uBITX at 25+ wpm with my bug and have it actually transmit what I send every time without introducing any garbage into the key stream.
I supply the schematic here for anyone wanting to see if the circuitry will help their CW operation. No PC board is available but the circuit is simple enough (2 resistors & two 2N7000 FET's per stage) that building it on a small piece of perfboard is easy enough to do.
Jim Sheldon, W0EB
Jim Sheldon
