I've found when aligning radios, such as CB radios, the SDR dongle is useful to detect carrier leakage on Single Sideband, and for detecting harmonics on 54 MHz.
In some service manuals these are part of the alignment procedure, and those without an expensive spectrum analyzer can use the dongle for this purpose.
It can also be used to monitor the quality of your transmitted CB AM or SSB signal. Just remember to turn down the RF gain on the dongle when transmitting, and use a dummy load on your CB radio too.
Sponge
In some service manuals these are part of the alignment procedure, and those without an expensive spectrum analyzer can use the dongle for this purpose.
It can also be used to monitor the quality of your transmitted CB AM or SSB signal. Just remember to turn down the RF gain on the dongle when transmitting, and use a dummy load on your CB radio too.
Sponge