Just wondering what some of you are using as your analog FM Modulation reference standard? Anyone have a favorite analog FM modulation monitor? Here's an excerpt from the Inovonics 531 modulation monitor manual:
FCC Measurement Method:
One reliable guideline in determining just how far you can go with respect to total carrier modulation is to be aware of how at least one government authority monitors a broadcasters signal. As far as we have been able to determine, the United States FCC does not use a commercial Modulation Monitor with a metered readout. Instead they connect an oscilloscope to the composite baseband output of a wideband FM receiver and look for deviations beyond a predetermined peak-to-peak amplitude. As divulged by one Field Engineer, the FCC is not looking for the occasional overshoot, but for consistent and flagrant overmodulation, which is invariably noticed and complained about before the station is flagged for scrutiny.
As Delivered:
The Inovonics 531 allows the user to select one of four integration times: 100µs, 200µs, 500µs, and 1.0ms. As delivered, the 531 is jumpered for the fastest (100µs) integration. This is the safest choice, but the one that consistently shows the highest total modulation reading for any given signal. Offered a selection, most broadcasters will opt for longer integrationz sometimes as much as 10ms! We feel that this long an integration period equates to fooling no one but yourself.€ The longest (1.0ms) integration afforded by the Model 531 is probably safe under nearly all operating conditions, though the user is cautioned to compare his modulation with that of his companions in the market to avoid sticking out like the proverbial sore thumb.
FCC Measurement Method:
One reliable guideline in determining just how far you can go with respect to total carrier modulation is to be aware of how at least one government authority monitors a broadcasters signal. As far as we have been able to determine, the United States FCC does not use a commercial Modulation Monitor with a metered readout. Instead they connect an oscilloscope to the composite baseband output of a wideband FM receiver and look for deviations beyond a predetermined peak-to-peak amplitude. As divulged by one Field Engineer, the FCC is not looking for the occasional overshoot, but for consistent and flagrant overmodulation, which is invariably noticed and complained about before the station is flagged for scrutiny.
As Delivered:
The Inovonics 531 allows the user to select one of four integration times: 100µs, 200µs, 500µs, and 1.0ms. As delivered, the 531 is jumpered for the fastest (100µs) integration. This is the safest choice, but the one that consistently shows the highest total modulation reading for any given signal. Offered a selection, most broadcasters will opt for longer integrationz sometimes as much as 10ms! We feel that this long an integration period equates to fooling no one but yourself.€ The longest (1.0ms) integration afforded by the Model 531 is probably safe under nearly all operating conditions, though the user is cautioned to compare his modulation with that of his companions in the market to avoid sticking out like the proverbial sore thumb.
