Hi everybody,
Since my first prototype of the K2 DATA port implementation, I did some
extensive test today during an outdoor portable operation.
I found that ground loop can occur on lower band... 40m or lower... And the
problem come from the PTT line.... that goes to ground during TX. Even if
the line IN and OUT are both isolated with an audio tranformer.
I also test today my DATA port with my SCS PTC-IIe modem and had the same
problem.
I finally found the problem and solved it !!
Like SCS (PTC-IIe manufactuer) said in their user manual. If you tranceiver
have an external power option, like found on Yaesu FT-8XX data connector,
YOU SHOULD USE IT. Do not power your modem from another power source, but
from the transceiver port itself. Like for the NUE-PSK, PTC-IIe or any other
TNC... always power your device with power from your transceiver.
This way, you will avoid ground loop that will harm your signal quality for
sure.
I just add one wire inside my K2 to the DATA port. I took the 12V line from
the AUX 12V connector inside the K2. This way, you will not have any more
problem and finally have an universal DATA port ffor almost any kind of
external device.
I will post a revised schematic on my website this week.
Like my previous modification, I always use RG-174 for inside wires. It does
prevent RF pickup during transmit and keep the signal as clean as possible.
I will also post a few more pics.
Another tip, apply acrylic coating spray on the back of the amplifier board
before applying the two way tape. It will prevent short circuit with any
electronic part with the chassis.
Best 73,
de J-F VA2SS
===
de J-F VA2SS
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