1. VS Series Transmitters Design Overview
Module 1 covers NV series product overview and installation requirements.
After the slide presentation do a show & tell using the transmitter pointing out the various PWBs, power supplies, RF modules, etc.

2. Design Overview
The VS transmitter project objective was to create a low power FM transmitter family.
Some of the basic design criteria included (must have):
Broadband, capable of operation from 87.5MHz to 108MHz.
19 inch rack mount chassis with minimal rack size
Output power levels to meet low power market requirement
Full SWR protection and operation at rated power up to VSWR of 1.5:1
Easy to install and operate
Can move between analog and HD or DRM at the touch of a button.

3. Design Overview
The design also needed features that would distinguish this family from other low power offerings on the market.
Some of the additional features considered (nice to have):
Integrated audio processing
Ethernet control
Audio over IP
HD upgradeable
Reliability and cost needed to be at the top of the design criteria to ensure a product that would be attractive to customers.
Can move between analog and HD or DRM at the touch of a button.

4. Design Overview
The basic transmitter block diagram is shown below. Innovation was required to take the VS family from a basic transmitter design to an industry leader.
Controller
Exciter
RF Drive
RF Amplifiers
Combiner
RF Filter
Power Probe
Can move between analog and HD or DRM at the touch of a button.
AC/DC Power Supply

5. Design Overview –RF Amplifier
Let’s take a look at some the parameters that guided the design decisions of the VS family.
Power Levels – Based on market data and RF amplifier power capabilities, it was decided to design 3 power levels: 300W, 1 kW, 2.5kW. The RF amplifier chosen was the SD2942 Gemini FET which had known performance and reliability from the V series and NV series transmitter. This amplifier is capable of producing 375W conservatively into 50 ohm load. This amplifier is capable of linear operation, has high efficiency and has a push pull design (low 2nd harmonic).
The 300W model would require 1 amplifier.
The 1kW model would require 4 amplifiers.
The 2.5kW model would require 8 amplifiers.
Can move between analog and HD or DRM at the touch of a button.

6. Design Overview –RF Amplifier
VS2.5 was the last transmitter in the family to be designed.
During the time of the VS300 and VS1 development, several significant events occurred:
It was realized that the 8 amplifiers and the associated combiners would occupy too much real estate to fit in a small (5U) package
A new LDMOS amplifier was being developed with 800W capability
This resulted in the VS2.5 adopting the LDMOS amplifier which was also very efficient, linear and capable of meeting the TX power requirements with only 4 amplifiers and therefore saving valuable real estate due to reduced combiner size.
Can move between analog and HD or DRM at the touch of a button.

7. Design Overview- RF Amplifier
RF Amplifier - building block for VS300 and VS1
Can move between analog and HD or DRM at the touch of a button.

8. Design Overview – AC/DC Power Supply
The AC/DC power supply needed to be small, efficient with a large AC operating range and low output ripple. The power supply used in the NV transmitter was the natural choice as it met the $/watt and W/inch3 requirements.
With a DC output capability of 2kW 40A typ), the 300W model required 1 power supply (lots of headroom!), the 1kW model required 1 power supply, and the 2.5 kW required 3 power supplies once PA efficiency and SWR were included in the power budget.
With the power supply chosen, this would set the AC input voltage for all models to be:
Vac, 1 phase, 50/60 Hz with Optional step up transformer available
for 120V operation
Can move between analog and HD or DRM at the touch of a button.

9. Design Overview – RF Drive
Knowing the gain of the final stage amplifiers and the output capability of the RF exciter stage, an RF driver was designed using the latest LDMOS technology. The VS300 required a one stage amplifier (10W capability) while the VS1 and VS2.5 required a 2 stage amplifier (150W capability). Power control for VS transmitter whilst in analog operation is achieved by varying the DC voltage on the final stage so the RF drive amplifiers could be operated in a constant power mode
Can move between analog and HD or DRM at the touch of a button.

10. Design Overview – Combiner
With only one amplifier, the VS300 did not require a combiner. However without the aid of a 3dB quadrature, the amplifier power rating needed to be reduced (330W max) in order to account for SWR conditions. (Amplifiers in quadrature tend to manage SWR better).
The VS1 with 4 amplifiers required a 4-way star combiner utilizing stripline design found in NV RF module. In order to achieve quadrature combining, the RF drive for a pair of the amplifiers was delayed by 90 degrees and compensated at the input to the combiner.
For the VS2.5 with higher power, a pair of Wilkinson combiners followed by a 3dB quadrature was used. The Wilkinson used a stripline design while the 3dB used broadside coupled lines.
Reject loads were sized appropriately for reasonable power capability under failure conditions.
Can move between analog and HD or DRM at the touch of a button.

11. Design Overview – Power Probe
The power probe for all transmitters utilized a stripline design optimized with the latest software tools and true RMS RF to DC converters for accurate power measurement even under digital operation. Directivity of the probes was measured at better than 25dB.
Can move between analog and HD or DRM at the touch of a button.

12. Design Overview – RF Filter
With the harmonic content from the amplifiers known, and broadband operation required, a multi pole low pass Chebyshev topography was employed for all transmitters. For added protection an RF choke was located at the TX output to shunt unwanted transients from entering the transmitter’s critical circuits.
Because the VS300 could also act as an exciter and be exposed to possible voltage transients while driving tube transmitters, a gas discharge tube was placed at it’s output for additional protection.
Can move between analog and HD or DRM at the touch of a button.

13. VS1Combiner& Filter
Can move between analog and HD or DRM at the touch of a button.

14. VS2.5 Combiner Filter
Can move between analog and HD or DRM at the touch of a button.

15. Design Overview – Controller/Exciter
The design of the controller and exciter was decided to be amalgamated onto a single PWB design thereby integrating the exciter into the transmitter. This would prove to be a significant design advancement for low power FM transmitter architecture.
State of the art RF generation circuitry was employed using quadrature digital upconverters which aided with keeping cost under control while providing a pure spectrum output. Additionally, an ARM processor was added which provided ethernet conductivity and control via Nautel’s award winning AUI interface. The ethernet doorway now added the capability of streaming audio over IP. USB ports added the icing on the cake for audio file storage and retrieval.
An agreement was reached with Orban allowing Orban audio processing to be integrated into the exciter/controller functionality.
Can move between analog and HD or DRM at the touch of a button.

16. Design Overview – Controller/Exciter

17. Design Overview – Controller/Exciter
The exciter/controller architecture allows for an unprecedented amount of modulation sources including:
Left and right
AES 1 and 2
Composite
SCA composite
SCA baseband
RDS data (internal generator)
IP audio Livewire, Shoutcast, Ice cast (Ethernet)

18. Design Overview – Controller/Exciter
The exciter/controller was design with remote control as a priority. With the ARM processor and traditional I/O, 2 remote control paths were now available:
Web Based Control:
From a web browser you can access most of the transmitter’s local functionality.
An Ethernet port is provided for remote connection to remotely monitor and/or control an VS series transmitter.
Discrete Logic Control:
All important status, telemetry and control of the VS transmitter’s operation is available such as on/off control and status, RF power level, power level adjustment, and system reset.
Includes 10 digital inputs, 16 digital outputs, and 4 analog outputs.
Each input is preset by Nautel but can be mapped by the user to any available digital control/status within the transmitter.
All digital inputs and outputs are defined using the AUI.
Read information on slide. 18

19. Design Overview – Controller/Exciter
Built in Web Browser allows for AUI accessibility with wide range of configurable displays.
Features:
- Advanced Instrumentation (Spectrum Analyzer, etc…)
Configurable meters
Exciter Control
- Linux OS
Explain AUI

20. Design Overview – VS Family
1 Amplifier
1 Switching Power
Supply
1 Preamplifier
VS1 W
4 Amplifiers
1 Switching Power
Supply
1 Preamplifier
1 Intermediate
Power Amplifier
VS2.5 W
4Amplifiers
3 Switching Power
Supplies
1 Preamplifier
1 Intermediate
Power Amplifier
1 Switching Power
Supply

21. Design Overview- VS300

22. Design Overview- VS300

23. Design Overview –VS1 Top

24. Design Overview –VS1 Bottom

25. Design Overview –VS2.5 Top

26. Design Overview – VS2.5 Bottom

27. VSHD Exciter
With the addition of the VSHD exciter, a VS transmitter can be configured to operate in FM+HD or HD only mode.
The VSHD uses the HD exciter core from the NV transmitter and features:
Adaptive Pre-correction
Pre-Equalization
Enhanced metering including output spectrum

28. Design Overview- Cooling
Ambient Temperature between 0°C (32°F) and 50°C (122°F)
Derate by 3°C / 500 m (2°F / 1,000 ft.)
Altitude 0 m to 3,000 m (0 ft to 9,750 ft.)
Humidity 0% to 95%, non-condensing

29. Design Overview- VS300 Cooling

30. Design Overview- VS1 Cooling

31. Design Overview- VS2.5 Cooling

32. Design Overview –Output Impedance
As with all Nautel transmitters, the design load is 50 ± j0 ohms. This obviously is best case and can not always be realized in the field so the design has the flexibility to operate into non-ideal loads.
VSWR
Rated Power achievable up to 1.5:1
Automatic power reduction above 1.5:1
Shutback above 2:1
Shutdown above 3:1
Read information on slide.

33. Design Overview –Output Connectors
The VS transmitters were designed to available with the most popular high quality RF output connectors:
VS300 –N type or 7/16 DIN
VS1 - 7/16 DIN or 7/8 EIA
VS /16DIN or 7/8 EIA
Read information on slide.

34. Design Overview –Conclusion
The VS series was launched in 2010 and now boasts more than 1000 units in the field.
Field performance has been excellent and user feedback has been positive.
The VS family revolutionized the low power FM market providing features and a cost that had not been available before.
It took a dedicated and caring team many long hours to design and develop such a special family of transmitters and we’re very proud of our accomplishment.
Read information on slide.