Farhan has said that the uBitx uses a low side BFO, below the crystal filter passband,
because with a BFO about 3khz higher on the high side of the crystal filter?
the harmonics of the 12mhz BFO beat with the harmonics of the 16mhz oscillator on the Nano
and create havoc.? ? I'd guess that you have an especially low 16mhz crystal on the nano,
and/or a pick of 12mhz crystals that happen to be especially high.
Your best bet might be to either replace the nano or replace the 16mhz crystal on the nano.
It might be possible to shield and filter the nano sufficiently somehow, but that would be tough.
Could be that hfsignals would consider replacing your Raduino, you might ask them.
Do you have somebody nearby you could swap out the Raduino with,
see if the problem follows the Raduino?
?
The ideal would be to buy or build an Arduino of some sort with the oscillator far removed from 16mhz.
That would allow us to choose high side second local oscillator injection (currently low side when operating LSB),
which might help improve opposite sideband rejection (we can choose the sharper 12mhz filter skirt)
and perhaps avoid some birdies.
Jerry, KE7ER
On Wed, Jan 24, 2018 at 12:49 am, John wrote:
2. Changes in tones frequency DO occur when:?
? ?2.1 The unit BFO frequency is changed (the most significant variation)
? ?2.2 When the calibration is changed (this changes the BFO frequency too)
? ?2.3 When I touch the pins of the SI5351 crystal
? ?2.4 When I touch the pins of the Arduino's crystal
