Problem reported in this thread solved. Bought and installed two optical isolators. One in ICOM serial line and one in GS232/G5500 serial line. Rotor position now reading correctly, but there was one more issue. Cables that I believed to be straight through were not; they were null modem. Should have used an ohm meter right away. Tests of pins 2 and 3 at both ends proved what the cables really were.
A warning: two null modem cables back-to-back to not make a straight through cable.
But there still are more problems with my sat system, which I will discuss in further posts.
Larry W7IN
On 4/15/2010 6:41 PM, Larry Gerhardstein wrote:
Jim, et. al., Thanks for the advice. However, after installing the USA-49WG and driver install for Windows 7 with help from Tripp Lite technical support, my system still does the same thing. I plug the serial cables to both rotor and transceiver digital interfaces and then to the 49WG and the same thing happens. Azimuth meter drops to zero and there is no control. Further it is now working worse than before, as I have neither control of rotor or transceiver. If measure the voltage between metal shields of the two cables, there is about 2 volts there. It sure looks like a ground loop, but where and how. I have no idea at this point. In 56 years a ham operator, I've never run into anything like this. Maybe RS232 isolators would fix this??? Seems like overkill.
Larry W7IN