Troubleshooting guide

Bulletin 639519 • Revision D May 2009 11-1

Section 11

Smart Bias Tee Issues

11.1 No Devices Found

• Verify that surge arrestor on coax line can pass dc. Two acceptable surge arrestors are

APTDC-BDFDF-DB and APTDC-BDFDM-DB. Other types may ground the dc voltage, preventing

voltage from reaching the actuator, TMA, etc.)

• Verify that the smart bias tees are installed correctly.

• Verify that the coax line doesn’t have a short by connecting ohmmeter between connector pin and

shield. (Line could have a short even if it sweeps OK.)

• Another device in the coax line (such as a cross-band coupler) may ground dc. You may need to

introduce a dc block in the line.

• Top and bottom bias tees may not be on the same coax line.

• See Section 12, TMA Issues.

• See Section 5, Isolate and Replace.

Note: For information on smart bias tees, see “Smart Bias Tees, Conﬁ gurations,

and Practical Usage” white paper, available on the Andrew website:

http:\www.commscope.com→andrew→eng→products→antennas→

teletilt→literature.