What symptoms may result from other signals interfering with a PACTOR or VARA transmission?

PACTOR and VARA are both connected digital protocols that use Automatic Repeat reQuest (ARQ) for error correction. This means the transmitting station sends a block of data and waits for the receiving station to acknowledge it. If interference corrupts the data, the receiving station requests a retransmission. When other signals interfere with the transmission, these data blocks are repeatedly corrupted. This results in frequent retries as the software attempts to push the data through, which in turn causes noticeable long pauses in the actual message transmission. If the interference is severe and continuous, the error rate may become so high that the software eventually times out, leading to a complete failure to establish or maintain a connection between the stations. Therefore, all the listed symptoms will occur.