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Intermodulation interference is a problem constantly lurking in the background,
were multiple productions are taking place simultaneously in relative close
proximity. In these cases, proper frequency coordination is a must.
Lectrosonics has developed a frequency coordination chart designed to help
users quickly locate intermodulation free frequencies.
The Compatible Frequency Chart divides the frequency blocks used in the North
American market into Row 1 and Row 2, then further divides each row into two
groups of eight frequencies each. These frequency groups are labeled A and B
and C and D, and correspond to the factory set frequency groups
(Groups A, B, C and D) used in the Digital Hybrid Wireless™ (400 Series) products. Understanding and using the Compatible Frequency Chart is not as
difficult as it first appears.
The following guidelines should be observed when selecting compatible frequencies:
1. Set 1 and Set 2 are NOT compatible.
Proper coordination requires that all frequencies be taken from either Set 1 or Set 2, but not a combination of the two.
(The remaining guidelines make the assumption that you are choosing frequencies within one frequency set.)
2. Frequencies within an individual frequency block in the same Set are compatible.
(Example: All 16 frequencies in Block 25, Group A and B)
3. Frequencies from adjacent blocks, but different Groups are compatible.
(Example: Block 21, Group C frequencies are compatible with
Block 22, Group D frequencies)
4. Frequencies from adjacent blocks and the same Group are NOT compatible.
(Example: Block 26, Group B frequencies
are NOT compatible with
Block 27, Group B frequencies)
It is highly recommended that you choose frequencies that are in the same set and same group. By following these guidelines, it is possible to locate a number of operating frequencies early in the production that are free from intermodulation, then refine the list during system setup.
The Frequency Chart is available for download as either an Excel Spreadsheet (xls) or a PDF file.