IAS is the abbreviation for ISO-ASYNCHRONOUS and SYNCHRONOUS modes. Iso-asynchronous modes have start and stop elements like Baudot, but the code words have an integer number of elements. The IAS function is used for the extremely accurate baud rate estimation of a synchronous or iso-asynchronous bit stream.

The automatic phase correction for the ideal bit center sampling (bit synchronism) is completely independent of the IAS function and is always active. The extremely accurate baud rate determination uses the number of necessary phase correction steps for the baud rate determination.

In modes working with an interrupted data stream such as PACKET-300, it may be advantageous to be able to switch off the baud rate correction to prevent drifting of the pre-selected baud rate. When the IAS function is disabled, any pre-selected variable baud rate will be treated in the same way as a fixed baud rate.

In most of the VHF/UHF modes the IAS is permanently disabled. This is due to the lack of phase coherence between successive data blocks. An exact measurement of the phase shift is not possible for an extended period of time.

In the event of adverse HF reception conditions (fading), enabling IAS may offer substantial advantages. The software will decrease the size of the phase correction steps in accordance with the verified, reduced phase errors, and thus prevent bit glitches and the resulting loss of synchronism. It is therefore recommended to enable IAS as a default.

Choose “on” and “off” to enable and disable the ias parameter, respectively.