"I Don't Want L-Band, I Want C-Band"

During the past three years we have been selling a large number of L-Band modems and Block Up Converters (BUCs). Currently, we are selling about five BUCs to a single transceiver. Not because the BUCs are necessarily better; the reason is price!

A typical VSAT installation has the antenna mounted outside with the transceiver mounted as close to the antenna feed as possible. The modem and other electronics are connected by a cable located in the back of the operations center. If this cable had to carry the original RF frequency of 4 to 6 GHz, it would need to be very thick and expensive. In order to cut down costs, satellite engineers designed transceivers that would take the high frequency from the antenna and then convert it to a much lower frequency. They called this new frequency "Intermediate Frequency (IF)". The advantage of this frequency conversion is that IF frequencies can be carried over long distances between the antenna and indoor equipment using cheaper cables.

To illustrate the difference between the two technologies, let me first review the 70 MHz modem and transceiver combination. I will use C-Band as my example, but principle remains true for Ku-Band as well.

The receive frequency of 4 GHz is collected by the antenna, then fed to an LNA and passed on to the receive port of the transceiver. Typically the transceiver is mounted on the antenna so only a short length of low loss cable is required between the LNA and the transceiver. Once the signal gets to the transceiver, it is converted from high frequency to an Intermediate Frrequency (IF) of 70 MHz and carried by a standard Co-Ax cable the distance from the antenna to the indoor equipment.

The transceiver contains all the frequency conversion and input/output power controls that are needed to send and receive the satellite signal. It must be waterproof and impervious to heat and cold. All of these features add to the cost of the transceiver, which is typically comprised of a power supply, SSPA, an upconverter, and a downconverter.

                A typical 20 watt C-Band transceiver will cost about $16,500 with a compatible modem costing $3,500 or more.

In an effort to reduce the price of the transceiver, a new scheme was developed that uses an intermediate frequency in the range of 900 to 1100 MHz. Even though much higher than 70 MHz, this L-Band frequency, as it was named, can still be carried long distances over cheaper cable.

The other change was to replace the transceiver with a much simpler and cheaper unit called a Block Up Converter or BUC. The BUC makes a simple frequency conversion and then acts as an amplifier sending the signal up to the satellite. The BUC is a "dumb" device compared to a tranceiver.

The power supply, radio settings, and frequency selections are now moved into the L-Band modem. The modem sits indoors and does not require environmental protection, but does cost more than a similar 70 MHz modem. Even so, the cost of the combination BUC, LNB, and L-Band modem is many thousands less the cost of the older system.

A typical 20 watt C-Band BUC will cost $7500 with the L-Band modem costing $4000. Prices for a Ku BUC is slightly differnt than C-Band, but the same ratio of price savings can be expected.

The only downside to the L-Band system is it's name. Many times when we offer the L-Band solution, the client will say that they don't want L-Band- they want C-Band or Ku-Band.....sigh!