New transmission standards are continuously being implemented. The digitization of television requires transmitter network operators to implement additional digital standards such as DVB-H or A-VSB. An expansion of the existing transmitter system is often not sufficient. Instead, a new system must be purchased. Before buying a news transmitter system, there are several issues to consider.
Future-proof
The era in which a transmitter system transmitted the same signal at the same frequency ended long ago. New standards such as DVB-H, MediaFLO and North Korea's T-DMB, DVB-T, DVB-T2, ATSC's A-VSB, China's DMB-T or Brazil's SBTVD-T require that transmitter systems offer maximum adaptability. Who knows which standards will become mandatory in a few years.
In addition, frequency assignments may change because of the numerous new services. Stations that operate on UHF channel 21 today may be assigned channel 56 tomorrow.
But broadband does not always mean broadband. Although many manufacturers offer systems for a complete frequency spectrum, the spectrum is actually divided into multiple subbands. If a channel is changed over a large frequency range, individual modules may have to be adjusted, or the replacement of hardware may even be necessary.
This is all the more important for operators of more than one transmitter system. Anyone who operates an entire transmitter network is glad if only a few spare parts have to be stocked, a benefit that also means real cash savings over the years.
Only a few manufacturers can provide suitable transmitter units for new standards. These are usually companies that participate in defining the standard and developing test and measurement equipment. That's because new standards are always accompanied by the front-end need for T&M instruments to be used in the development of new chipsets and receivers. If T&M instruments and transmitter systems are also based on the same software platform, system operators will be up-to-date from the start.
There are still regions where new analog transmitters are being installed. Their operators often face uncertainty about which digital standard will be used in the future. This requires a transmitter system designed with flexibility in mind. Only such an investment will be future-proof.
Older transmitter systems should be completely replaced because they cannot handle evolving standards. The new standards for mobile TV cannot be used in many older transmitter systems. Expensive modifications only make sense at first glance. The remaining components are still old, and efficiency is low compared with the latest transmitters.
The uncertainty as to the future standard or frequency for a digital channel is often matched by the difficulty of predicting which output power will be needed. In some cases, relatively low power is deliberately used at the beginning to keep the investment low. Here, it is especially advantageous if a manufacturer provides solutions that allow expansions when they become necessary.
Well-cooled
The lower the operating temperature of a transmitter system, the more efficient and long lasting its components will be. The latest generation of transmitters for high output power use liquid cooling instead of the conventional air cooling. Thus, the systems are considerably more compact than before.
The better the cooling, the less heat will be dissipated, thus eliminating the need for air conditioning. If systems operate around the clock, the positive effect on the electricity bill soon becomes obvious.
A closed cooling circuit is highly recommended because the cooling system can operate at a very low pressure. Moreover, the risk of corrosion-causing oxygen or other impurities getting into the system is almost zero.
Smaller footprint
Today, transmitters with DVB power of up to 6kW and ATSC power of up to 8.5kW are accommodated in a compact 19in rack, for example. Who would have dreamed this possible even five years ago? Thus, space requirements at the station are reduced. Less space means less enclosed area and less maintenance. For transmitter network operators leasing space, the compact designs help to reduce these monthly payments.
Higher efficiency
In recent years, some manufacturers have been able to further increase the efficiency of their transmitter systems. The latest generation of LDMOS technology (lateral double-diffused MOSFET) in particular have offered improvements in digital TV transmitters by more than 20 percent. This translates to a 5kW DVB transmitter using 50,000kWh to 60,000kWh less per year. Converting these savings to euros at current energy prices shows that the slightly higher price of a technically superior model will amortize within a short time.
However, many manufacturers were not able to overcome the challenges presented to create this type of transistor. A major hurdle was the production of broadband transmitter systems with the current transistor technology. Because amplifiers aren't linear by nature, some suppliers can linearly cover only a frequency band of 100MHz. Only a few amplifiers can be flexibly used across the entire UHF range (470MHz to 862MHz).
In today's environment, transmission systems that are not flexible can lead to the loss of great sums of money as new add-ons are continuously introduced in the complete frequency spectrum. Retrofitting will cost more than two or three times as much as the amount saved on the initial purchase.
Easy servicing
When purchasing a new transmitter system, the focus should be on easy servicing. Owing to an intelligent electronic control unit, errors can be detected and displayed before the system fails.
Expensive on-site personnel will no longer be required around the clock because remote maintenance has been greatly improved in recent decades. Excellent transmitter systems of the latest generation have an IP interface and can be maintained from anywhere in the world if necessary.
Remote maintenance, better known as remote access, is now an easy task using a Web browser or SNMP connection. Today, it does not matter if the monitor is in the same room or at the opposite end of the country. If major problems occur, the manufacturer can also be consulted without incurring travel expenses or an additional delay.
A concept that uses uniform modules in one or more product families is another advantage for operators of large transmitter networks. Thus, spare-parts provisioning will be minimized. A uniform operating concept reduces training for the service teams.
Energy-saving
In the long term, the upfront costs for purchasing a transmitter system are secondary to the total costs incurred over the product's entire life. Higher quality minimizes the need for servicing and extends the depreciation period.
Liquid cooling only adds to this benefit. Plus, there is the significantly enhanced efficiency from the (skillful) use of LDMOS technology. In total, this means large savings in energy costs, which can certainly add up over the many years a TV transmitter is kept in operation. Anyone who purchases a system with exceptionally high efficiency quickly achieves a high return on investment. The latest models save so much energy that replacing older units is well worth the money.
Especially in times of rising energy costs around the world, transmitter systems that save on electricity are a must. The lower energy consumption will not only benefit the environment. A transmitter network operators and TV providers will enjoy lower broadcasting costs.
Summary
When purchasing a new transmitter system, it is important to check the details. Only highly flexible and broadband transmitter systems guarantee a solid future-proof investment.
Thomas Loichinger is head of product management, terrestrial transmitter systems at Rohde & Schwarz.
Advantages of new transmitter systems
- High level of operating reliability
- Low operating costs
- Easy servicing
- Low space requirements
- High flexibility
