Simulcast Radio Systems optimize the use of available spectrum by synchronizing transmission from multiple overlapping antennas. Under this system, all baseband (VF) channels are assigned to identical RF frequencies at each transmitter. This arrangement makes best use of the available RF band and permits mobile units to leave radios set to the same frequency while traversing the entire service area.

In an "overlap" area, receivers pickup signals from two or more antennas. To have clear reception, signals have to be synchronized - four ways:

1 RF carrier frequencies are matched to within a few Hz.

2 The phase response of the VF channels are matched to within 10 degrees.

3 The amplitude response of the VF channels are matched to within 0.1 dB.

4 The absolute time delay of the VF channels are matched to within 10 microseconds.

Convex Corporation produces PC controlled equipment and software to handle the VF matching. VF transmission is routed through a Convex 2042 Simulcast Equalizer. The 2042 provides response correction, gain, and time delay adjustment needed to match all channels.

This is accomplished with three functional blocks:

FLAT GAIN - Amplifies or attenuates all frequencies by a variable factor to compensate for difference in loss to diverse transmitters.

DELAY / AMPLITUDE EQUALIZER - Selective frequency controls shape delay and amplitude responses. High resolution adjustments permit all channels to be set to a common, flat characteristic.

BULK DELAY - Delays all frequencies by a variable time factor to compensate for difference in transmission delay to diverse transmitters. The range is 0 to 500,000 microseconds in 1mS. steps!

Channel characteristics are measured using the Convex 806ARTIMS. The 806A is a general purpose transmission test set which is used to measure signal amplitude, amplitude response, delay response, and round-trip time delay. (It also measures noise, signal to noise ratio and impulse noise.) A 2 minute auto-test feature measures delay and amplitude response - simultaneously. The response data is saved as a PC file, and subsequently used to calculate equalizer settings.

Convex C40CSS Control Set Software is used to determine equalizer settings which "flatten" the delay and amplitude response. Inputs are measured response files. Outputs are "setting" files which are downloaded to the 2042 Equalizers.

Related Products:
Audio: Delay module - remote
Audio: Delay voice land lines
Audio: Equalize voice land lines or analog mux-voice channels

Last update 5/4/06.

Simulcast Solutions®LLC 18 Port Meadow Trail, Fairport, NY, USA, 14450 TEL: (585) 223-4927, FAX: (585) 223-3255 info@simulcastsolutions.com