FMX™ Stereo Generator

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Inovonics' 705 is a full-featured FM Stereo Generator (or "Stereo Coder" in European parlance) which includes the FMX™ "Coverage-Extension" Transmission System as an easily-installed plug-in option.


  • Digital synthesis of pilot(s) and subcarrier(s) gives maximum stereo separation and stable operation with no trimming adjustments or other routine maintenance.

  • Internal phase-compensated lowpass input fltering provides complete pilot and SCA protection.

  • Built-in peak overmodulation protection and proprietary filter overshoot control circuits assure full modulation without need for additional composite processing.

  • Adjustable composite equalization can correct for STL or other system non-linearities.

  • The 705 can interface with a variety of Inovonics or other audio processing systems.



Frequency Response (preemphasis defeated)

+/-0.5dB, 25Hz-16kHz; -20dB or better at 10Hz, -60dB or better at 19kHz.


<0.1% THD in baseband and subcarrier at 90% modulation.

Noise (below 100% modulation, Pilot OFF)

-75dB or better in baseband and subcarrier; 38kHz residual and “digital” noise above 54kHz, -60dB or better.

Stereo Separation

Better than 55dB, 25Hz-15kHz.

Crosstalk (M/S or S/M)

Better than -60dB.


19kHz, +/-1Hz; <2% THD (distortion products better than 55dB below 100% modulation); Pilot injection level adjustable between 6% and 12% relative to 100% modulation.

Inputs (LEFT and RIGHT)

Active-balanced, bridging; accept line input levels between -15dB and +15dB for 100% modulation. (0dB = 0.775V r.m.s.)

Input Filtering

7-pole, phase-corrected, active-elliptic “FDNR” lowpass with defeatable overshoot compensation circuitry. Third-order Chebyshev highpass section.


Selectable for 75- or 50- microsecond or “flat” transmission characteristics.


Single-ended (unbalanced); selectable 75-ohm or “zero” (voltage source) impedance. Level adjustable between -5 and +12dBm (0,5 to 3V r.m.s. or 1.2 to 8V p-p).

Overmodulation Protection

Integral with input filter overshoot compensation circuit and defeatable with same.

Digital Synthesis Sampling Rate

608kHz (16X subcarrier).

FMX™ System Option

User-istallable auxilliary plug-in circuit board with all parameters preset.

Power Requirement

105-130 or 205-255 VAC, 50/60Hz; 8 Watts.

Size and Weight

1 3/4” x 19” x 8”