NCE Wireless signal issue

Since instalation of the wireless system mid 2009, we've sometimes had issues with the handheld cab establishing communication with the main controller. This cab works fine when it is plugged into the control bus not using radio communication.

The cab has since been sent back for repair and the problem appeared to be solved when we got it back. However, as of early May 2010, the problem appears to be coming up again.

ISSUE:
At times, the only way to establish communicate wirelessly after power up (pressing E-Stop button once & waiting about a minute) is momentarily unplugged the control cable from the antenna and reconnected it.
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When the LCD displays "LOC: XXXX" XXXX being the last engine number run on the cab, the system has established communication.

NCE said they will take another look at the problem but they also want to look at the antenna.