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When troubleshooting RF issues, and when surveying challenging RF environ-
ments, it’s important to have a spectrum analyzer capable of measuring the
frequency that you are working with.
An attenuator should be used to protect the
input, when connected to a source of RF power such as the repeater or a
powered DAS.
Both Uplink and Downlink should be measured. Downlink should be measured
on the donor cable and at the output (server) port of the powered up repeater,
and Uplink at the lead from the DAS (on fiber/powered DAS’s, where the lead
would connect to the server port on the repeater) and at the donor port with the
repeater powered up. Measurements may also be necessary at server
antenna locations. Your spectrum analyzer will need to be equipped with a
whip antenna for this.
Resolution Bandwidth (RBW) should be set at 200 kHz for GSM and 1 MHz for
CDMA. If you cannot select these values, the closest available values should
be used. Video filter should be about one tenth of RBW. Other settings like
span are whatever is appropriate. One should also make sure that there are
no signals above the top of the screen.
If you cannot see an adjacent out of band signal when using the 1 MHz RBW
filter, you can decrease the RBW, to see the close-in-frequency signals. Be
sure to set the RBW back when you want to measure the power level.
RF Notes:
To prevent overload of the DSP input stages, the maximum measured level of
in-band or out of band signals should be less than -50 dBm when the DSP gain
is set to 85 dB, -40 dBm when set to 75 dB, etc. This applies when there is
one dominant signal and applies TO BOTH THE DOWNLINK AND UPLINK. If
there are two dominant signals, and the gain is set to 85 dB, then the level of
each signal should be kept to less than -53 dBm. With three signals, each
should be less than -55 dBm. With ten signals each should be less than -60
dBm. This latter reduction prevents the composite power of the multiple
signals from exceeding an acceptable level. Add fixed attenuators in line with
the donor antenna line/DAS feed to keep signals below the levels indicated
above.
Suggested spectrum analyzer setting:
Summary of Contents for CSI-DSP85-C
Page 1: ...CSI DSP85 P CSI DSP85 C CSI DSP85I P and CSI DSP85I C Installation Manual ...
Page 14: ... 15 Functional Block Diagram ...
Page 37: ... 38 Notes ...
Page 38: ... 39 Notes ...
Page 39: ...960 1041 002 revD ECO 2151 ...
