Chapter 5 - Return Loss Measurement Testing; Introduction - Deviser SitePROFILER User Manual

Chapter 5 — Return Loss Measurement Testing

Introduction

This chapter provides an overview of performing Return Loss measurements with the E7000L SitePROFILER
Cable Analyzer. The Return Loss measurement is used to characterize the cable and antenna system in
order to ensure that the cell site is performing in accordance with established standards.
Underperforming cell sites typically exhibit a high level of signal reflections, due to impedance mismatches
within the cable and antenna system. Impedance mismatch issues often contribute to blocked or dropped
calls, poor data rates, and an overall undesirable performance in cell (or section of cell) coverage. Thus,
the Return Loss performance of the antenna system – included the cable feedline – is a critical factor in the
service and maintenance of an RF transmitter system.
Return Loss and VSWR both display the match of the system, but they show it in different ways. The return
loss displays the ratio of reflected power to reference power in decibels (dB). The return loss view is usually
preferred because of the benefits of a logarithmic display; for one, it is easier to compare a small and large
number on a logarithmic scale. The return loss scale is normally set up from 0 to 60 dB, with 0 being an open
or a short and 60 dB being close to a perfect match.
Reflection measurements are generally performed with the antenna connected to the cable feedline, or
by replacing the antenna with a Load at the end of the RF cable.
To begin a Return Loss measurement, press the Menu button to open the measurement mode desktop,
then tap the Cable & Antenna mode icon. In the Measurement main menu, select Return Loss.
Which reflection measurement should I use?
Your specification (test procedure) will ordinarily direct you to make either a Return Loss or VSWR
measurement. Typically, system sweeps are performed in Return Loss mode, while component sweeps are
performed in VSWR mode.
For your convenience, the E7000L SitePROFILER can perform Return Loss and VSWR sweeps simultaneously
while in Dual Display mode.
NOTE: The larger of the values of the Return Loss measurement, the better the impedance match. Thus a
Return Loss measurement of 42dB represents a much better impedance match than one of 25dB.
Conversely, in VSWR, better impedance matches are indicated by smaller values.
E7000L SitePROFILER
Handheld Cable/Antenna Analyzer
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