I've built an interface between my computer sound card and the Accessory
jack on my Pegasus. This seems to work fine. I'm attempting to add PTT
control via a computer serial port. I've tried two different interfaces, the
one printed several times in QST that uses a transistor, a resistor and a
couple of diodes. In this interface, the grounds of the radio and the
computer are connected, With my Pegasus (and also with it's predecessor Omni
V) I get some hum on my transmitted signal, if the PTT interface is
connected to the computer serial port. If I unplug the interface and use
other means to key the Pegasus, the transmitted signal appears hum free. I'm
just reporting results from monitoring the signal with the TX monitor. I
figured that since the grounds were common in the interface that that might
be the source of a ground loop, so I rebuilt the interface using an
opto-isolator where nothing is common. I still get the hum.
On other thing to mention that may be a factor. I recently added dedicated
110V electrical wiring for my ham shack. I now have a home run directly to
the breaker box and thus I know that the ground pin on the 110V plug is
wired properly. Previously, I was using a 2 prong outlet that had been
replaced with a 3 prong outlet, but I don't know if the ground wire was
really any good. My station ground is a couple 6 foot copper ground rods
buried a few feet from the electrical ground. I ran a piece of heavy cooper
wire from the station ground to the electrical ground rod, but it is not
silver soldered, just an acorn clamp on both ends.
Mark
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