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MORE MODIFICATIONS TO RT85 
By Paul VK3TGX
Recently when trying to finally get my RT85 on air, I observed the noise on tx audio fault that has been the subject of
previous mods from Ian, (my rig was totally unmodified) However I didn't like cutting the ribbon cable as that meant 2
cords running from the rig to the head, a bit messy I thought.  So I prodded around in the head and found that putting
a 100nf capacitor from pin 6 to pin 4 of U7, LF351 op amp provided a 90% plus fix to that problem.
Subjectively it seemed to work a bit better that Graeme VK3XTA's rig that has had U7 removed and the ribbon cut to
include some shielded audio cable.

Another mod tried by Ian was to connect the mic directly to the rig bypassing the head altogether.  This seems to have
the same level of success, however PTT control is read by the micro processor from the head - the PTT line from a
directly connected mic has to be routed back up the ribbon cable to the remote head!  (there are spare wires)

Later on I plan to completely replace the ribbon cable with some shielded data cable, earthed directly to the rig and
the head case to provide maximum shielding.  This should servery reduce the crud radiated into other rigs in one's shack.

Another quick mod would be to fit some large ferrite beads to the power cable, etc to try and stop any crud at these points.

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