Modifying the BITX40 for Upper Sideband
Because some digital modes require Upper SideBand (USB) to work properly, many people have been wondering how to get the BITX40 on Upper Sideband. Well, I’m here to show you- it’s pretty easy!
First, we need to understand that to get the BITX40 on Upper Sideband, we just want to change from a negative offset VFO (12mhz BFO minus 5mhz VFO = 7mhz)
to a positive offset (19mhz VFO minus 12mhz BFO = 7mhz) and that takes us from Lower Sideband to Upper Sideband. To allow the BITX40 to work on Upper Sideband, you do have to remove c91 and c92 as shown to the right.
The results work, although I do have a rather loud squeal when lowering the volume- some uncontrolled oscillation. When I have that figured out I’ll update the post. For now, it only happens on USB. Please check out the video below. It explains how to use the BITX40 on Upper Sideband further and shows a demonstration of the modification: