Receiver Improvenents.

All modules are build in. Now it is debugging time.

First I made the receiver operational.
Some problems that I had:

• Audio distorted.
• Banpass tuning not enough range to be useful for USB
• Attenuation of first xtal filer  too high.
• First xtal filter in not wide enough for SSB.
• Oscillation in audio path.

These problems were solved but there is room for improvement.

The first SSB xtal filter at 9 MHz contains just 4 xtals. The shape factor can be improved.
The second  xtal filter is at 6MHz that is used for passband tuning. It also contains 4 xtalsThe bandwidth is not optimal for SSB. It is usable but it should be wider. Now it is 2 KHz wide at -6 db. It is usable but not optimal. Shape factor is not really good so SSB signals can be heard.
In the future I will rebuild these xtal filters to optimize performance.

A problem that needs to be solved is the software. Sometimes the display or the microcontroller crashes/hangs. It seems to be related with the new pushbuttons that I use. During development I was using on/off switches .No crash was seen back then. The pushbuttons suffer from bouncing.

Now the receiver works but it needs improvement.
But first I will make the transmitter work. Then the transceiver is usable.
After that the improvements will be made one by one.