FM STL Link Microwave Aural Transmitter 1.4-2.5GHz-5W

STL Link Transmitter
Band 1.4-2.5GHz-5W

Our STL Transmitter Link, transmits Cristal and Clean High Quality Audio Sound From Studio to Transmitter Site-B1.4-2.5GHz-5W-Worldwide Immediate delivery

A studio link transmitter, studio transmitter link, or STL is a special type of equipment used in broadcasting industry.


This transmitter are the core of a high quality, synthesised studio-to-transmitter link (stl), to be used for broadcast repeaters in conjunction with any standard FM or AM transmitter. They are an evolution of the previous extablished series stl whose main circuitry is still extensively used here with a new controller, user interface and software and more advanced oscillators in a compatible 2u 19" case. They allow the reception of mono or stereo signal and its retransmission without using any additional stereo-coder on the receiving end: in both cases the LF output signal from the receiver must be sent to the stereo input (linear or not pre-emphasised) of the local FM rebroadcast transmitter.

The stl is built for several different frequency slots from VHF to the SHF range. Two main models are built: one for the 200÷960 MHz and the other for the 1300÷2500 MHz range. While the exterior cabinet, the controls, the basic circuitry and the performances are the same, some internal components vary or are specifically tuned as required to cover this wide frequency band. Usually these components are the local oscillator, the power amplifier and the input/output filters The factory adjusted frequency slots are 10 to 50 MHz wide and must be specified in the order. In the preset sub-range, the frequency and power of the transmitter may be freely changed on the field. The receiver may require some more adjustment for wider frequency displacement: in fact the adoption of narrow, low loss input filters permitted to achieve the best possible rejection of interfering signals in the band at the expense of some frequency agility. So nearly 8-10MHz may be used without any retouching but wider variation up to 50-60MHz will require retuning of the input filter.

Being the apparatuses completely digitally controlled, they are extensively on field programmable by front panel or remotely in every respect. The alphanumeric display permits easy and accurate metering, adjustment and continuous monitoring of modulation levels, power, operation and internal parameters. All these information are externally available on the same RS232 I/O port that may be used to remotely control the transmitter. In addition to the serial I/O,some signals and controls are available on a parallel I/O socket for easy interfacing with others analog controllers or supervisory systems. A powerful 3-levels password management permits a very high degree of security and privacy as may be required in different situations.

The LF input and output levels are precisely adjustable over a broad range, by means of 0.5dB stepwise variable attenuators. The transmitter has also an auxiliary input, specifically designed for RDS and SCA encoders. A modulation monitor output permits to control other transmitters or STL's with the same internally processed high-quality mpx signal. Furthermore, the system is optimised to be compatible with external digital companding encoder/decoders and to provide RDS and SCA signals, with almost no attenuation.

Optional top-quality stereo encoder/decoder boards may be factory installed on the transmitter/ receiver or field retrofitted with minimum required technical skill. The powerful internal software and monitoring functions recognise their presence and enable the functions. A universal switch-mode power supply permits operation in the extended 95-250 V ac range with no intervention and a 24 V back-up battery input is provided too.


The transmitter and receiver set are fitted in the same sized cabinet and are nearly identical on the front view. In fact they differ for the name on the front panel and the display and for the rear panel connector's accommodation.

Both the equipment are clean and easy to control from the front panel through a single knob. The wide alphanumeric display and a simple self-explanatory menu drives navigation through the various options. A single fast push on the jog knob acts as an "Enter" or confirmation while pushing for a longer time is interpreted as "Escape".

Some leds signal at a glance proper functioning and warning states. Two red led signal warning status, "Alarm"and"Limiter".Abi-stableyellow/greenledsignals"Ontheair" whileafourthonesignals"PLL Lock": both these two should be green in correct operation.

All equipment inputs and outputs but RF monitor are allocated on the rear panel. They are:

  • The mains supply IEC320-type outlet, which incorporates the mains switch and the fuses. An additional earth screw for system earthing and a 24V= battery backup socket pair. In alternative the mains outlet with fuse-holder and the mains switch may be separate components
  • The RF antenna connector, N-type
  • The L & R stereo analog audio channels input on balanced XLR-type connectors (L input is used only with internal Stereo Encoder option).
  • The AES/EBU stereo digital audio input on a balanced XLR-type connector which may be used as an alternative to the analog input (this is a special option and may be used only in conjunction with the internal Stereo Encoder option).
  • The wide-band external processed stereo or composite signal input on a grounded unbalanced BNC connector
  • A frequency limited (20k ÷ 100kHz) auxiliary channel input on a grounded, unbalanced BNC connector for a RDS or SCA signal.
  • A LF modulation output for monitoring, RDS external synchronisation or re-broadcasting purpose, BNC-type
  • A RS232 Dsub9 female remote serial control port, inverted wired.
  • A parallel control port, Dsub9 male type

No internal or external preset is needed to correctly perform on 110 - 240V~ mains range


Frequency error <2,5 ppM
Frequency drift <1 ppM/year
RF output power 7W / 15W (215÷960 Mhz)

2W / 5W (1.4÷2.6 Ghz)
Max allowed reflected power 1W / 2W
RF harmonic products <-60dBc
Rf spurious products <-70dBc, -80dBc typ.
Audio/Mpx input level -3.5 ÷ +12.5dBm

@ ± 75kHz deviation
Audio/Mpxinput 10k ohm/600 ohm, bal./unbalanced
Common mode rejection >50 dB, >60dB typ. (20÷15000 Hz)
Audio input connectors female XLR type
Auxiliary channel input level -12.5 ÷ +3.5dBm @±7.5 kHz dev.

-24 ÷ -8dBm @±2 kHz dev.
Aux channel input 10kohm/BNC-type
Monitor LF output 0 ÷ +10 dBm @ ±75kHz dev.
Pre-emphasis time constant 0/50/75μs±2%
S/N noise ratio (30÷20000Hz rms) >77 dB, 82 typ. (mono)

>74 dB, 77 typ. (stereo)
Modulation distortion, 30÷15000 Hz <0.02% @ 75kHz dev.
Stereo crosstalk >50 dB (100÷5000 Hz)

>45 dB (50÷15000 Hz)
Audio channels response 30Hz÷15kHz±0.1dB
Out of band audio attenuation >50 dB @ F≥19 kHz
Deviation limiter 0 ÷ +7.1 dB, adjustable
Mpx composite response 10 Hz÷100kHz ±0.1dB
Auxiliary channel response 10÷ 100 kHz ±0.2dB
I/O lines RF disable, RF power, On-the-Air, alarm, RS232 control and monitoring
Mains absorption 50 Wmax @ 110-240V~(Po=5W)

Battery absorption ≤1.8A @ 24 V= (Po= 5W)

≤3.0A @ 24 V= (Po= 15W)
Dimensions, without handles 19" 2 un. std. Rack


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