The frequency band determines the type of receiving antenna and downconverter (if needed). LPTV signals are received by the cable modem using a normal outside TV antenna, possibly with an amplifier but paying more attention to the signal level than one would with an analog television set. The level must be close to the high end of the range acceptable to the modem, as the signal is more likely to fade than increase in level.

MMDS, MDS, and WCS require a small antenna integrated with a downconverter mounted on the roof or on the side of the building. These low-cost units are one-third the price of the cable modem. The antennas may be flat arrays, one foot square with 17-dB gain, or dome-shaped designs with similar characteristics. Other products use partial parabolas, two feet in diameter, or cast Yagi antennas, two feet long. Most downconverters allow a choice of internal gain as well as antenna gain so that output signal level can be as close as possible to 0 dBmV for the modem.

The following are points to note in a wireless environment:

• Locate the antenna to minimize multipath.
• Make sure the antenna is located to receive the direct signal rather than a stronger reflected signal off a building which may vary in level.
• Set the signal level close to 0 dBmV.
• Work with the downconverter vendor to achieve the simplest selection of amplifier gain and antenna gain for the coverage area to minimize the number of different models needed.
• Use the appropriate path-loss calculations for microwave links. The calculation for multiple modulators through a common transmitter (sub-channelization) is a little different from a single signal on a transmitter.
• A downconverter installation engineered for a cable modem can also support video service. The reverse may not be true as the cable modem has specific level requirements.
• The nominal signal in a wired cable environment is 0 dBmV in 75 ohms. The cable modem tuner/demodulator will accept a limited variation in input level. Depending on manufacturer, model, frequency of operation and MMDS environment, the path loss is stable except for multipath distortion (ideally removed by the cable modem adaptive equalizer), and the antenna or downconverter gain can be selected to provide the right level to the cable modem. In the case of LPTV, path fading is more common but an outdoor antenna with LOS operation will minimize the level variations from multipath.