An off-air Low Power FM (LPFM) transmission audit
Radio Inspectors recently visited the Dargaville area early to track and assess the source of a previously unaudited Low Power FM (LPFM) transmission.
The General User Radio Licence prescribes limits, conditions and a schedule on the operation of LPFM. Section 5 of the schedule specifies a maximum field strength of 112dBµV/m at a reference distance of 10 metres from the transmitting aerial in a 100 kHz resolution bandwidth (of the measurement receiver). Because the signal appeared stronger than expected, and an off-air audit does not require the assistance of the licensee, signal strength measurement was promptly commenced.
After correction for all factors, the measured field strength was calculated as 126dBµV/m at 10m within 100 kHz; 14dB over the limit prescribed. This indicated that the output of the transmitter was slightly over 10 Watts e.i.r.p. Also noted was excessive occupied bandwidth levels against both the LPFM licence schedule and the applicable Table 3 limits prescribed in the Radiocommunications (Radio Standards) Notice 2008.
As the transmitter was not operating in accordance with the licence conditions, an infringement fine was issued to the company responsible.
10 November, 2009 9:19 am 
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