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Comtech EF Data CDM-760 User Manual

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Appendix J

Revision 2

CDM-760 Advanced High-Speed Trunking Modem

MN-CDM760

J–17

J.5.2.2 Calculating CnC R atio from Ca rrier t o Noise Rati o (C/ N) on a

Spectrum Analyzer

For this example, assume Site A is running a link to Site

B (referred to as Link 1), and Site B is running a link to

Site A (referred to as Link 2):

CnC Ratio = C/N Interferer – C/N Desired + 10log(SR Interferer /

SR_Desired)

CnC Ratio at Site A = C/N Link 1 – C/N Link 2 + 10log(SR Link 1 / SR

Link 2)

CnC Ratio at Site B = C/N Link 2 – C/N Link 1 + 10log(SR Link 2 / SR

Link 1)

CnC Ratio from C/N

C/N (dB)

Symbol Rate (Msps)

CnC Ratio (by Carrier Direction)*

Link 1

Link 2

SR

Link 1

SR

Link 2

CnC A

(Site A Site B)

CnC B

(Site B Site A)

9.5

7.5

5.0

6.5

+0.86 dB

-0.86 dB

Notes:

From the standpoint of Site A:

CnC Ratio = 9.5 – 7.5 + 10log(5.0 / 6.5) = +0.86

From the standpoint of Site B:

CnC Ratio = 7.5 – 9.5 + 10log(6.5 / 5.0) = -0.86