STL Studio Transmitter and Receiver Link
FM Radio Equipment

GENERAL DESCRIPTION

This transmitter and its companion the receiver 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 previously established STL series, 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.
These allow the reception of mono or stereo signals 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 the VHF to the SHF range.
Two main models are built: one for the 200-960 MHz range, and the other for the 1300-2500 MHz one.

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 site.
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 programmable on site via the 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 this information is externally available via the same RS232 I/O port, which 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 other analog controllers or supervisory systems.

A powerful 3-level 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 also provided.

DESIGN

These radio links were specifically designed to comply with the latest international standards and the requirements of advanced broadcasters, meeting tighter specifications than usually required, at an affordable cost.

Great care was spent into producing a Hi-Fi-quality modulated signal, with low residual noise and distortion. The RF signal is also free from spurious and harmonic components to a higher degree than required by CCIR, European, USA and most other national standards.

RECEIVER RADIO LINK MODELS

MODEL	DESCRIPTION
TK-STL-R1	Link Receiver Band 170 - 490MHz (band max ±10MHz)
TK-STL-R3	Link Receiver Band 820 - 960MHz (band max ±10MHz)
TK-STL-R5	Link Receiver Band 1.4 - 2.5 GHz (banda max ±5MHz)

RADIO LINK RECEIVER: TECHNICAL FEATURES 

PARAMETER	VALUE
Frequency Ranges	200~960 MHz - 20MHz sub-band
Type of Modulation	FM Class F3
VCO Tuning	25 MHz
Frequency Stability	± 2.5 ppm (Better on request)
Synthesizer	Step 25KHz
Image Rejection	60dB Typ.
RN Noise Figure	6dB or lower
Stereo Separation	> 45 dB @ 1 KHx
Distorsion	< 0.5% (TYP 0.2 % @ 1KHz)
Base Band	30 Hz - 60 KHz within 0.08 dB
S/N Ratio	> 72 dB with 0.2 mV input (Typ 78 dB)
Deenphasis	50 or 75 μS int. selectable
RF Connectors	N-F 50 ohm
B. Band-IF Conn.	BNC-F
Base-Band Imp.	< 30 ohm
Cooling	Forced air
P. Temp. Range	0 ÷ +45°C
Maximum Umidity	90%
AC Supply	100 ÷ 240 Volt; 47 ÷ 63 Hz
Dimension	1 Units Rack 19” 44 cm Depth
Weight	5.8 Kg