2001.08.21 - NLARC Repeater Site Inspection

Reason for Inspection:

The 146.34/94 repeater has been exhibited a squelching problem that has made the transmitter retransmit what sounds like audio oscillations that resemble intermodulation distortion.

Course of Action:

Jim Byrd and John Parker visited the site and performed the following items:

• The identification of the repeater controller connections was accomplished. A sketch of the repeater controller card was made.
• The VSWR of the antenna system was checked at the repeater and at the antenna.
• The repeater control cards inside the 146.34/94 repeater rack were cleaned with an eraser and the cards were reseated.
• The correct receiver squelch control was located.

Results:

• A finalized sketch of the repeater controller card functions and connections will be made available on the website.
• The full-up antenna system VSWR is still 1.4/1. Some subsequent tuning of the j-pole antenna can make this figure better. The VSWR at the antenna is 1.3/1.
• Some oxidation was removed from the card edge connectors.
• The receiver was found to be undersquelched. The squelch was set to a "tight" setting. Also, the roar sound did not occur the entire time the repeater/duplexer was on the dummy load. It was noted that the repeater could still be brought up from 15 miles away with one Watt despite the tight squelch setting.

Further Action:

• Install a short section of new coaxial cable to a spare j-pole antenna. The existing heliax that is on the catwalk may have internal problems we cannot detect by any other means but elimination. If the roaring sound dissappears then this may indicate the heliax be no longer suitable for repeater operations.

Web page operations: James E. Byrd
Responsible NASA Official: Richard S. Eckman