The paper introduces a new channel access method called Multiple Access with Collision Avoidance (MACA) for amateur packet radio, addressing the "hidden terminal problem" and the "exposed terminal problem" that are common issues with Carrier Sense Multiple Access (CSMA). MACA is inspired by CSMA/CA and the "prioritized ACK" scheme, and it can be extended to include automatic transmitter power control, potentially increasing the channel's carrying capacity. In the hidden terminal situation, stations cannot hear each other, leading to collisions. In the exposed terminal case, well-sited stations waste transmission opportunities due to unnecessary deference to distant stations. MACA overcomes these issues by extending the Collision Avoidance (CA) part of CSMA/CA, allowing stations to inhibit transmission based on the receipt of RTS and CTS packets, even if they do not hear a response. The paper explains how CSMA/CA works, detailing the Request To Send (RTS) and Clear To Send (CTS) dialogue. It then proposes turning CSMA/CA into MACA by removing the Carrier Sense (CS) component, focusing instead on inhibiting transmission based on the receipt of RTS and CTS packets. This approach is illustrated with examples and metaphors, such as a cocktail party where speakers pause to let others speak. MACA can also be seen as a single-channel, time-multiplexed form of Busy Tone Multiple Access (BTMA), but it uses the same channel for both data and busy tones, making paths more likely to be symmetrical. Collisions between RTS packets are minimized with a randomized exponential back-off strategy, and MACA can bypass the dialogue for smaller data packets to reduce overhead. The paper discusses the potential for automatic power control in MACA, which could significantly improve channel reuse. It also explores applications for MACA, such as creating practical single-frequency amateur packet radio networks, particularly useful in emergency situations and temporary operations. Finally, the paper concludes by highlighting the need for further simulation and experimental work to evaluate MACA's performance and compare it with other multiple access methods.The paper introduces a new channel access method called Multiple Access with Collision Avoidance (MACA) for amateur packet radio, addressing the "hidden terminal problem" and the "exposed terminal problem" that are common issues with Carrier Sense Multiple Access (CSMA). MACA is inspired by CSMA/CA and the "prioritized ACK" scheme, and it can be extended to include automatic transmitter power control, potentially increasing the channel's carrying capacity. In the hidden terminal situation, stations cannot hear each other, leading to collisions. In the exposed terminal case, well-sited stations waste transmission opportunities due to unnecessary deference to distant stations. MACA overcomes these issues by extending the Collision Avoidance (CA) part of CSMA/CA, allowing stations to inhibit transmission based on the receipt of RTS and CTS packets, even if they do not hear a response. The paper explains how CSMA/CA works, detailing the Request To Send (RTS) and Clear To Send (CTS) dialogue. It then proposes turning CSMA/CA into MACA by removing the Carrier Sense (CS) component, focusing instead on inhibiting transmission based on the receipt of RTS and CTS packets. This approach is illustrated with examples and metaphors, such as a cocktail party where speakers pause to let others speak. MACA can also be seen as a single-channel, time-multiplexed form of Busy Tone Multiple Access (BTMA), but it uses the same channel for both data and busy tones, making paths more likely to be symmetrical. Collisions between RTS packets are minimized with a randomized exponential back-off strategy, and MACA can bypass the dialogue for smaller data packets to reduce overhead. The paper discusses the potential for automatic power control in MACA, which could significantly improve channel reuse. It also explores applications for MACA, such as creating practical single-frequency amateur packet radio networks, particularly useful in emergency situations and temporary operations. Finally, the paper concludes by highlighting the need for further simulation and experimental work to evaluate MACA's performance and compare it with other multiple access methods.