Hello,
I found the source of the noise. (It's not directly 50 htz, but near to be heard.
My assembly being in "scratch", the small snore came from the sound potentiometer. it was enough to connect the mettalic part of it to the ground. Hence the importance of putting the assembly in a metal case.
In spite of doing my measurements, I notice this signal of about 20mv at the output of the demodulator (When no signal on the antenna, put it to ground)? which is after the filter SSB (go to Q70 --> M1? -->M2? --> input of the audio amplifier).
it won¡¯t fit in the audio amplifier , but I was wondering if it could be filtered, or if it was due to an unbalanced demodulator or something else (?)
?
YOU WROTE:
(De)Modulator
The post filter signal is strong enough to not need an IF amplifier, so we directly take it to a balanced (de)modulator made out of two matched diodes. It is important to use matched diodes here as the same circuit is also used to modulate during transmission. Balance controls are pesky circuits, they are easily unbalanced and setting them properly is more difficult than finding two diodes with the same forward resistance and soldering in the pair. An easier option it to just order a small strip of the inexpensive BAT54S which come as pre-matched pair for a few pennies each. We use the remaining CLK#0 output of the Si5351 to drive the BFO. The carrier is permanently fixed to generate upper sideband signal. The sideband is inverted by flipping the second oscillator between 33 MHz and 56 MHz. ?When the second oscillator is at 34 MHz, the upper sideband propagates either way without inversion as 33 + 11 = 45 MHz. When the second oscillator is at 56 MHz, the 45 MHz is generated as 56-11 = 45 MHz. Note that in the second case, the 45 MHz signal will decrease in frequency as the 11 MHz signal is subtracted from 56 MHz, thus achieving sideband inversion. A few minutes of pencil and paper work will be required to figure out how this works.
On my assembly, it is a set of diode made-up (BAT54SLT1G-dk_Diodes-Rectifiers-Arrays).? 2 diode in the same package
I¡¯ve still planned a location to put BAT54S diodes in case.
If the problem comes from there, do you have a method to test? a pair 2 diodes??
cdt
Gerard