Radio World International Article


In today’s competitive broadcast environment, knowledgeable buyers have a difficult time justifying several thousand dollars for a 25-watt exciter/ transmitter combination. That is why BEXT recently introduced the LEX 25, a complete FM transmitter for $1,995. With more than 80 units [1996] sold since its introduction, this unit is the price/ performance leader.

Since technical quality and reliability were high on the list of desirable features, the design centered around getting the most value for the money spent. A single motherboard, heat sink and back panel design provide effective convection cooling. This eliminates the need for an internal cooling fan with its inherent reliability problems. The front panel consists of a single power switch and eight status LED’s. Unusual in this price range, the unit is a completely crystal-controlled, frequency-agile and broad-band amplifier. The frequency is easily set in 10 kHz increments by direct reading digit switches. If your frequency is 103.7 MHz, just set the first switch to 1, the second switch to 0, etc. There are no complicated binary codes to figure out. Placing these switches on the rear panel helps keep unauthorized adjustment to a minimum. In addition, the power output trim pot is located on the rear panel.

The VCO uses a short piece of coax as the oscillator inductor. This clever design eliminates the problems of microphonics and vibration that have plagued many designs in the past and allows an unprecedented 80 dBm signal to noise ratio.

Other features include balanced or unbalanced composite inputs, two additional subcarrier inputs and an internal jumper for pre-emphasis should the unit be used as a stand-alone monophonic transmitter.

Operation may be at 120 or 220 volts, 50 or 60 Hz allowing worldwide compatibility in a variety of configurations. In addition, the simple power supply uses a single-ended 24V source to provide the necessary voltages. The unit can be powered by two automotive batteries in series as an emergency or permanent installation. DC connection and protection circuits are already provided.

With the optional audio processor/ stereo generator, a complete standalone package for satellite feed or translator operations may be put together by the broadcaster. Since the unit includes a built-in low pass filter it can also be used as a stand alone transmitter/ booster.

An internal comparator circuit will keep the power within a 0.5 dB range despite temperature or aging effects. This circuit also provides VSWR protection and automatic foldback of the power should there be a problem with the antenna or load. A circulator may be added to match unusual load conditions if necessary. Levels are set for standard 3.5 v P-P but a trim pot allows an adjustment over a 12 dB range.

With a full two-year warranty and a bargain price, the LEX 25 series provides an attractive option for today’s equipment buyers.

For further information contact BEXT at (619) 239-8462 or fax your request to (619) 239-8474.