Just as there is no lowest power for QRP, there is no smallest antenna. As antennas get smaller, they tend to approach, but never reach 0% radiation efficiency. If a smaller antenna has say, 50% radiation efficiency, you can compensate by doubling the transmitter power. To anyone receiving your signal from some distance, there will be no observable difference.

If you can't double the transmitter power, then you can use a modulation technique that doubles the energy per unit of information. For example, you could switch from AM to SSB, or you could halve the bitrate for a digital modulation. If you can't do that, there's something else you can do. See How can I know over what distance or at what speed I can communicate?

Just as there is no lowest power for QRP, there is no smallest antenna. As antennas get smaller, they tend to approach, but never reach 0% radiation efficiency. If a smaller antenna has say, 50% radiation efficiency, you can compensate by doubling the transmitter power. To anyone receiving your signal from some distance, there will be no observable difference.

If you can't double the transmitter power, then you can use a modulation technique that doubles the energy per unit of information. For example, you could switch from AM to SSB, or you could halve the bitrate for a digital modulation. If you can't do that, there's something else you can do. See How can I know over what distance or at what speed I can communicate?

Just as there is no lowest power for QRP, there is no smallest antenna. As antennas get smaller, they approach, but never reach 0% radiation efficiency. If a smaller antenna has say, 50% radiation efficiency, you can compensate by doubling the transmitter power. To anyone receiving your signal from some distance, there will be no observable difference.

Just as there is no lowest power for QRP, there is no smallest antenna. As antennas get smaller, they tend to approach, but never reach 0% radiation efficiency. If a smaller antenna has say, 50% radiation efficiency, you can compensate by doubling the transmitter power. To anyone receiving your signal from some distance, there will be no observable difference.

If you can't double the transmitter power, then you can use a modulation technique that doubles the energy per unit of information. For example, you could switch from AM to SSB, or you could halve the bitrate for a digital modulation. If you can't do that, there's something else you can do. See How can I know over what distance or at what speed I can communicate?