Hamtronics USB Computer Control

The project illustrates the use of USB connection which is a more convenient way to interface to a computer for the Hamtronics receiver.

A device designed as a 5-channel crystal controlled receiver is the Hamtronics R139 WX FAX Receiver, specifically intended for reception of the polar orbiting weather satellites that broadcast on the 137MHz weather band. The reception of the wideband FM signal from the satellites is allowed due to the wideband IF of the receiver. It can scan the 5 channels and automatically stop on an active channel and works well with a strong signal.

Allowing the computer to determine the currently tuned channel is the basic idea of the computer control modification. The connection to the computer is through a DLP-USB232M serial interface mounted in a small project with 8-pin connector to the back of R139 receiver. Using this USB to Serial module makes it very simple to convert a serial port based design to USB because of freely available drivers.

Two sections divide the circuit consisting of the radio side for determining the selected channel and the computer interface side where powers are drawn from the radio and USB bus respectively.

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