Each receiver front-end contains filters or other band-limiting components to place constraints on the observable RF input frequency range. Each front-end incorporates one frequency conversion with limits both on the LO input frequency range and on the IF output frequency range. Several of the front-ends provide choices for RF or IF filters, selectable through the M/C system.
In order to use a receiver, the LO1 frequency must be set so as to produce an IF1 signal in the proper range. Constraints on IF1 and LO1 settings for each receiver front-end are given in Figure1. For most observations, the default value of LO1 should be calculated by tuning the desired sky center frequency to the recommended IF1 center frequency.