Problem solved.
Just to re-state the issue: strong tones within the passband, mostly fixed in ferquency. Some slight variation in frequency when scanning through the menu items. Also strong tones outside the passband (near 6400Hz and 14900Hz). These were fixed in frequency and would change with BFO frequency adjustments.
I also had noises when turning the tuning encoder each time the frequency was changed. I thought these were normal as they were mentioned in the Bitx40 rig.
I bought a cheap Arduino on eBay and after some struggle I changed the Nano, re-programmed it and all came good. The tones within the passband are gone and the ones outside the passband can be eliminated with a careful choice of BFO frequency.
Also the tuning noises have disappeared.?
So it must have been a bad Arduino in all logic.
As an interesting aside, when chasing this issue I changed the first two mixers VFOs thereby changing the alignment between the 45Mhz filter and the 12Mhz one. I noticed that the default values produced a signal around 8dBs lower than when "re-aligning" the two passbands.
If anyone is interested I can share the code for this test (I simply re-assigned the RIT menu item and had an extra variable which was added to the first two VFOs so that the net received frequency stayed the same, but the first IF was shifted correspondingly).
Please note that I found the removal of the Arduino a challenge and resorted to cutting the edges out of the Arduino board with a
Dremel and cut the plastic spacer between each pin to be able to de-solder each one individually. I have not mastered James technique obviously!
Since I have mounted the display remotely and have space towards the front of the Raduino, I opted to put some female headers so that I can plug/unplug the Arduino, just in case.
Hope this helps,
73, John (VK2ETA)
