384352 BPL Measurement Procedure

Publication Number: 384352	Rule Parts:	Publication Date: 06/01/2021
Keyword: BPL Measurement Procedure

First Category:	Equipment Authorization Process *
Second Category:	General [Equipment Authorization Process]

Question: If a proposed system has a signal with a bandwidth from 4 to 22 MHz, the midband frequency of 13 MHz., corresponding to the wavelength of 23.06 meters and the wavelength for the lowest frequency is 4 MHz (wavelength of 74.95 meters), how far out should the measurements go along the line, given these potential measurement points down the line:
Wavelength, midband:0, 1/4, 1/2, 3/4, 1, 1&1/2, 2 And Distance Down Power Line (m) : 0 5.765, 11.531, 17.296, 23.06, 34.592, 46.123.
If the 2-wavelength point for the midband frequency exceeds the half-wavelength of the lowest frequency (which would be 37.475 meters), should the 2 wavelength measurement point be included?

Answer: Appendix C (Measurement Guidelines for Broadband Over Power Line (BPL) Devices Or Carrier Current Systems (CCS) and Certification Requirements For Access BPL Devices) of Report and Order FCC 04-245 (https://docs.fcc.gov/public/attachments/FCC-04-245A1.pdf) states the requirement as follows:
"Testing shall be performed at distances of 0, ¼, ½, ¾, and 1 wavelength down the line from the BPL injection point on the power line. Wavelength spacing is based on the mid-band frequency used by the EUT. In addition, if the mid-band frequency exceeds the lowest frequency injected onto the power line by more than a factor of two, testing shall be extended in steps of ½ wavelength of the mid-band frequency until the distance equals or exceeds ½ wavelength of the lowest frequency injected." Thus, in the example cited in the question, the measurement at 1.5 wavelengths of the mid-band frequency does not meet the requirement that the greatest measurement distance must equal or exceed 1/2 wavelength of the lowest frequency injected, but the measurement at 2 wavelengths of the mid-band frequency does meet that requirement; consequently, measurements at both the 1.5 and 2 wavelength distances are required.

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