What is a frequency allocation?
A frequency allocation assigns a part of the radio spectrum to one or more radio services. It helps prevent incompatible services from using the same spectrum without coordination.
ITU allocation table
Article 5 of the ITU Radio Regulations contains the international Table of Frequency Allocations. It shows which services may use different frequency bands in the ITU Regions. Some allocations are primary and others are secondary.
Primary and secondary services
A primary service has allocation status shown in the table with capital service names. A secondary service must not cause harmful interference to primary services and cannot claim protection from harmful interference caused by primary services. It must also follow the applicable sharing conditions.
ITU Regions
The world is divided into three ITU Regions for frequency-allocation purposes. India is in ITU Region 3. A band allocation can differ between Regions, so an international band chart must be read with the correct Region column and footnotes.
National frequency permissions
The international table does not, by itself, give an Indian operator permission to transmit. The Indian Government specifies the frequency bands, emissions and power for each ASOC category. The operator must use only the current authorised range and conditions.
Band edges
A band edge is the upper or lower frequency limit of an authorised band. The entire transmitted emission must remain within the permitted limits. A carrier close to the edge may still produce sidebands outside the permitted range.
Emission and power limits
The permitted emission types and maximum transmitter power depend on the ASOC category and the current Government schedule. Never copy a power figure from another country or an old licence chart and assume it applies in India.
Band plans
IARU band plans are voluntary operating arrangements developed by the amateur community. They help separate CW, narrowband, voice, image and digital activity. They do not replace national frequency regulations or the conditions of an ASOC.
Choosing an operating frequency
Before transmitting, check that the frequency is within the authorised band, suitable for the emission, and not occupied by another station. Also consider band plans, local coordination and any special restrictions.
Out-of-band emissions
A transmitter must be tuned accurately. Unwanted energy must not be radiated outside the authorised frequency limits. Filters, correct alignment and suitable operating practice help control unwanted emissions.