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64 Chapter 3
Overview of the Test Set’s Built-In Tools
Using RF Tools Program
Typical cable fault return loss measurements. Return loss is a
ratio of input power to reflected power. For example, if 100 Watts was
applied to a cable and 10 Watts was returned, the return loss is 10 dB
(10 log (100/10)). In the same example, if 1 Watt was returned, the
return loss is 20 dB (10 log (100/1)). Typical return loss measurements
for the cable loss test are listed below:
• Open-Circuit Cable = 0 dB
• Short-Circuit Cable = 0 dB
• 50-Ohm Terminated Cable = 20 to 30 dB
• Antenna = 10 to 20 dB
Return loss measurements below 25 dB should be considered
excellent. For best results, the cable output should be terminated in
50 ohms.
Entering Cable Length
The greatest accuracy is obtained when you enter a cable length
slightly greater than the actual cable length, considering length
uncertainty. If you are not sure of the cable length, enter a value 1.5
times the estimated length. Depending on the return loss of the
antenna or device at the end of the cable, you may see a high relative
mismatch displayed at the actual length of the cable.
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