LNBF

Direct Broadcast Satellite (DBS) dishes use a low-noise block converter with an integrated feedhorn (LNBF). Often times, small diplexers allocate the resulting intermediate frequency signal in the same cable television wire that transmits lower-frequency signal from a terrestrial antenna. A separate diplexer then divides the signals to the integrated receiver-decoder (IDS) of the DBS set-top box and to the receiver of the TV set.

Up-to-date Ka band systems use more intermediate frequency blocks from the LNBF. One of these intermediate frequency blocks will cause disruption to UHF and cable TV frequencies that are more than 250MHz, ruling out the use of the diplexers. The other block is superior to the original with frequencies up to 2.5 GHz. This would oblige connection of the LNB to first-class all-copper RG-6/U cables. This would also add up to the higher electrical current and electrical power requirements for multiple dual band LNBFs.

For some free-to-air (FTA) and satellite Internet, seasoned individuals recommend a universal LNB. Majority of the DBS signals in North America use circular polarization, rather than linear polarization. This uses a different type of LNB for suitable reception. With this, the polarization must attune to the counterclockwise and clockwise directions, instead of the vertical and horizontal.

In the case of DBS, the voltage provided by the set-top box to the LNB establishes the setting of the polarization. In multi-TV systems, a dual LNB enables both to function at once using a switch that serves as the distribution amplifier. The amplifier then transmits the proper signal to each box in accordance to the selected voltage. The most recent systems may choose polarization and which LNBF to utilize by transmitting DiSEqC codes. The earliest satellite systems power-drove a rotating antenna on the feedhorn, during the time when there was only one LNA or LNB on a very large TVRO dish.

Weather Problems

One of the problems encountered by people using LNB is loss of signal due to moisture accumulation, especially during inclement weather. During snowy or rainy conditions, the snow or rain collecting on the LNB tends to interrupt the signal. Wiping off the moisture from the LNB will cause the signal to return. Some would even tie a plastic bag around the device just to keep moisture away.

An LNBF with appropriately constructed shield over the device can eliminate the problem with moisture accumulation and signal loss. This protects the device from precipitation while not obstructing signal reception.