Recently the Edision Mio line of receivers running TNAP5 has added the feature to allow display of SNR values for a transponder that is not locked. Here is a practical example of why this is useful.
Montana PBS on 99W on a sunny day here can be 11.0 dB. But it can be tough to receive when it is raining or about to rain. Its C/N lock value is 6.6 dB. This is the minimum SNR at which you can see the channel. It is now currently 6.0 dB.
Before this new feature, I might have guessed the signal was too low to see but I would have been guessing. It also might simply be off air. Now I can measure the unlocked value and KNOW that the signal is too weak for me to see.
Unlocked SNR of Montana PBS:
Locked SNR of PBS:
Montana PBS on 99W on a sunny day here can be 11.0 dB. But it can be tough to receive when it is raining or about to rain. Its C/N lock value is 6.6 dB. This is the minimum SNR at which you can see the channel. It is now currently 6.0 dB.
Before this new feature, I might have guessed the signal was too low to see but I would have been guessing. It also might simply be off air. Now I can measure the unlocked value and KNOW that the signal is too weak for me to see.
Unlocked SNR of Montana PBS:
Locked SNR of PBS: