"7.1997 corresponds to the 300Hz audio, 7.197(0) corresponds to the 3000Hz audio"
Really? Is a SSB LSB RF signal coming in with the audio inverted? It certainly is not coming from the IF that way.
If inversion happens, it must happen twice (or an even number of times) for it to be readable.
john
AD5YE
---In BITX20@..., wrote :
Ken:?? I think?sideband inversion is a lot simpler than that and can easily be explained without resort to "negative frequencies."
Just consider an LSB signal coming in at 7.2 MHz.? It will be spread out from about 7.1997 down to? 7.197 Mhz.? 7.1997 corresponds to the 300Hz audio, 7.197 corresponds to the 3000Hz audio.
Assume your IF and crystal filter ate at or around 10 MHz.
You have two options for the VFO:? 2.8 MHz?or 17.2 MHz.
With 2.8 MHz you take the sum product out of the mixer.?7.1997+2.800=9999.7 MHz?? 7.197+2.800=9997? That's an LSB signal at 10 Mz. NO INVERSION
With 17.2 MHz you take the difference: 17.2-7.1997+10.003MHz????? 17.2-7.197+10.003 MHz..? That is a USB signal at 10 MHz? SIDEBAND INVERSION!
It helps to draw this all out.? See attached.?
This proves the rule:? Sideband inversion only takes place when you SUBTRACT the signal carrying the modulation FROM the signal without the modulation (the VFO or LO).
Please let me know what you think about this explanation.?
73? Bill N2CQR
