A diode is often put across a relay coil to prevent the "kick" from blowing out the relay driver or disturbing other circuits when the relay opens. What is the major disadvantage of using this diode?

It slows down the release of the relay

It ends up failing as a short, and fries the circuit controlling the relay

The relay can only be activated with one polarity

It rectifies RF and holds the relay on

Answer: It slows down the release of the relay

Ampliifer T/R switching times are sometimes important, especially if you use QSK or some of the digital modes. The relays are often the slowest part of the system , and many speedup circuits have been used to address the slow ON time of relays. The catch diode can ruin these efforts by allowing the coil current to keep flowing and extending the release time, making the OFF time the slow link in the chain.