LO1B: GBT Receiver Room LO used for Doppler tracking
Local Oscillators 1 A and 1 B are located in the GBT receiver room and are used for the first down conversion of the input, amplified signals to a convenient intermediate frequency for transmission to the Jansky building. For most GBT receivers, only LO1A
is used for down conversion. The LO signals must be routed to the receiver for use. The required power levels and Doppler tracking modes are specified by the observer or engineer.
For diagnostic purposes, one of the LO1A
may be coupled to the receiver to test frequency stability and/or correct receiver operations.
The KFPA receiver array uses both LO1A
for normal down-conversion and input of signals to the IF rack. Normally LO1A
is used for doppler tracking and setting the sky (observing) frequency. In the KFPA IF chain, LO1A
is doubled before use in the mixer.
has a fixed value of 6.8 GHz.