The Hamtronics R139 WX FAX Receiver is a 5 channel crystal controlled receiver specifically intended for reception of the polar orbiting weather satellites that broadcast on the 137 MHz weather band. The receiver has a wideband IF that allows for reception of the wideband FM signal from the satellites. The received audio from the receiver is passed to a computer sound card where a program such as WxToImg is used to decode it to an image.
The R139 can scan the 5 channels and automatically stop on an active channel. This works well provided one has a strong signal. If the signal is weak or subject to fading the squelch will close and the scan will resume during the satellite pass which results in a truncated satellite image. For reception of the satellite pass horizon to horizon manual selection of the received channel and running with open squelch is needed.