Total coverage of the territory using one single frequency without interference.

SYES wishes to share its pioneering experience in broadcasting with state-of-the-art digital technology, offering an interference-free radio coverage with a single frequency from multiple overlapping emitting centres. A milestone has been achieved by synchronizing analogue transmitters with results never seen before.

The 90.9 frequency was used to converge multiple FM signals over the same territory, obtaining excellent audio quality over the whole coverage area.In its determined commitment to technological innovation, Syes has conducted tests of iso-frequency in Frequency Modulation (FM) with a technology which allows to offer radio coverage without interference in shadow areas using a single frequency from various emitting centres.

The state-of-the-art digital technology provided by Syes has made it possible, for the first time, to synchronize with absolute technical precision the emissions from repeaters of a public network.

It is worth mentioning that we are not talking of the so called Single Frequency Network (FM) which is widely used in linear areas to provide coverage by using one frequency on a motorway which, for its own nature, it is pretty easy to achieve: it is in fact enough to locate transmitting points to such a distance that the coverage achieved by one transmitting point does not affect the one that follows and the one that precedes hence taking advantage of the natural signal degradation.

The scope of this pilot was, in some way, completely the opposite; where the SFN takes advantage of the signal loss, the iso-frequency aim is to get the most out of the strength of a plurality of signals hitting a common area.
The test, which demonstrated positive results, consisted of using the same frequency (90.9 MHz) simultaneously from the three FM transmitters, converging its emissions over the same cover zone.

This scenario is impossible using conventional analogue technology, as the strong interference generated between transmission centres makes the signal inaudible where the coverages overlap. However, this test demonstrated a successful reception result and excellent audio quality in the wide geographical area under study.

The test was conducted in an orographically clear area and, for the purposes of this study, a signal with 100% interfering level was planned between the three emitting centres, with direct line of sight between them in more than 80% of the territory, and radio electrically by more than 95%.

Measurements showed that, far from interfering, signal strength increased (by almost +8dB on average) at those points where all three emissions summed up, which is equivalent, for practical purposes, to multiply by 6.3 times the value of the power received from a single transmitter. All this, with very low signal-to-noise ratio levels.

These results greatly improve the recommendations of the International Telecommunication Union (ITU) on the application of such systems to analogue FM.
The synchronization of centres has now considerably improved those early results, thanks to the combination of the most advanced technology available on the market and specifically designed for this scope. The incorporation of new GPS geolocation receivers that offer greater stability and accuracy, as well as state-of-the-art Direct Digital Synthesis Modulators (DDS) of the greatest stability and precision and the use of high performing IP audio transport chain made eventually possible something that had never been achieved before.

This technology also affects the use of the radio spectrum by greatly optimising it and improves coverage in areas of complicated orography.
In addition, it allows to significantly reduce transmission power without affecting coverage, it requires simpler installations in the broadcasting centres, and improves energy efficiency thus minimizing both the power consumption and the maintenance costs.