@Shadetree Mechanic - you raise a good point.
The mode you are using - play the part in how the signal gets "decoded".
USB and LSB are "mirrors" of each other.
But, using USB to decode LSB, even when you're able to tune into the exact frequency, the signal sounds garbled - because it's INVERTED - it's not going the "right way" for the receiver to track it.
Same thing happens when LSB tries to decode USB - again, the frequency is there, you can tune to it, but the signal is INVERTED - you hear "garbled" because you're in the wrong mode to decode it.
Think of it as a freeway, a highway - so to speak.
Upper Side band is ABOVE the Carrier frequency - going to the top of the graphic - in US, you're on the Right side traveling forward - towards the horizon - the carrier contains information (your white line) that tells you how to interpret your side of the road.
Lower side band is still on the highway, it's using the information in your Carrier - but is BELOW the carrier frequency - so think of it as information traveling on the highway, but to interpret it, you see it arriving towards you travelling the opposite direction towards and past you - so you see it and can decode it, but you have to understand it is in the oncoming lane..
You can pass information by changing your frequency - you can even go into the OPPOSITE lane if you wish by SHIFTING your frequency, but don't expect that traffic to understand your intent or even be able to process the signal your sending on this highway. - because it's not in the MODE of that lane.
- So whether your travelling forward, or going back home on this same highway
- - just remember that the lane you're in, you see the traffic ahead of you in your lane as able to travel along with you...
- It's the opposite lane the Opposite MODE - is the trouble - it's not going to understand you or your intent - in being there in their lane in the wrong MODE
To understand the traffic you either follow their direction - or you can change YOUR direction to follow the other lane - but to process the other lane, you need to be travelling in the same direction - with it.
It's about as basic as I can make it to help understand that your carrier is the center line - your audio information travels above and below it, but if you use the wrong lane you can't process it.