All that will do is invert the sideband so that anyone with an SSB receiver just switches to the opposite sideband and offsets the carrier frequency by the amount of your "audio inversion gizmo".
O/k so you have an original two tone test signal 300 Hz and 1 Khz.
You feed that through your magic 5Khz audio inversion gizmo box so that the frequencies that come out are (say) 4.7 Khz and 4.0 Khz
If you modulate a 10 Mhz carrier you get
USB 10.0047 and 10.004 frequencies
LSB 9.9953 and 9.996 frequencies.
If you transmit just the USB I can receive that perfectly clearly if I use a receiver tuned the LSB but tuned 5khz higher
10.005 - 10.0047 = 300Hz
10.005 - 10.004 = 1Khz
The same trick works if you transmit on LSB, I just switch to USB and tune 5 Khz lower.
9.995 + 9953 = 300Hz
9.995 + 996 = 1Khz
You have scrambled nothing.
Either signal would sound perfectly normal, and anyone would never even realize it was supposed to be scrambled.
Thanks Tony, but my goal is NOT to scramble the conversation so that it cannot be heard.
My point is to be able to make two homemade DSB transceivers to communicate together, whereas they normally cannot, because of the opposite sideband problem at the reception.
One of them has to be tuned to an offset so thet the TX USB and the RX LSB lie together. But in that case you cannot recover the audio because you try to recover a USB signal on the LSB.
By the audio inversion, I try to propose a system (if it can be done) to do so.
For example:
DSB transmitter A, transmits a DSB signal, but the content of the sidebands (audio) will be scrambled.
Explaining only what happens for the USB sideband for the shake of the example, a 1KHz audio tone will appear 1KHz away from the suppressed carrier, whereas a 2KHz audio tone, will appear 2KHz away from the suppressed carrier.
If the audio tones are previously scrambled (inverted), prior to modulation, the 2KHz audio tone will appear closer to the suppressed carrier than the 1KHz, is that right?
If the above line is true, then the DSB receiver will receive the DSB signal and in the RF domain, it must be tuned so that the suppressed carrier frequency is above the suppressed transmitted carrier frequency. This will make the LSB of the receiver to lie on the frequencies of the USB of the transmitted signal.
The transmitter LSB and the receiver USB will never interfere, as they are apart, due to the offset of the receiver carrier (tuned frequency).
The transmitter USB will lie to the receiver LSB frequencies.
In a normal audio modulation this would be heard as trying to receive an USB signal on the LSB, but in our case, because the audio is inverted, a descrambler on the receiver can recover the original audio tones.
That is my idea, how does it sound?
After detection, the recovered audio will be scrambled and it needs to be discrambled (re-inverted) so that the audio is recognized.