Question from an ARTCC controller
 

I work at Houston Center. My question is: If an acft loses its transponder, how does this affect its ADSB capabilities? I'm under the impression you would lose ADSB as well.

It would depend on which frequency the ADS-B out is using. Here is a good source for ADS-B training. If a transponder is the ADS-B-out source (1090 MHz), than yes, ADS-B would be lost. If a separate 978 MHz (978UAT) transmitter is the ADS-B-out source, than ADS-B should continue to function.

Freeflight Systems | NextGen Avionics - ADS-B Solutions - ADS-B University

To expand a bit...

Most GA owners (not flying in Class A / FL180+) will probably keep their existing Mode A/C transponder and install a completely separate 978 MHz ADS-B "out" transmitter, or a 978 MHz ADS-B transceiver (UAT). So if their ADS-B goes out, they'll still have their original Mode A/C transponder.

Most large commercial aircraft will probably get a 1090 MHz ADS-B transceiver to replace the existing Mode S transponder. Loss of the ADS-B transceiver would typically mean loss of Mode S capability as well.

I'm asking because I'm curious as to whether or not I'd lose a plane on my scope if they lost their ADS-B the same way I'd lose one that wasnt ADS-B if it lost its transponder.