[amsat-bb] Re: usb to serial adapter woes

Larry Gerhardstein gerhardstein at montana.com
Thu Apr 29 21:40:09 PDT 2010

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

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