| Filter: |
A device used to reject all but a specified range of frequencies. A bandpass filter allows only those signals within a given band to be communicated. A rejection filter, the mirror image of a bandpass filter, eliminates those signals within a specified band but passes all other frequencies. |
| Frequency: |
The number of vibrations per second of an electrical or electromagnetic signal expressed in cycles per second or Hertz. Frequency Response : The change of gain with frequency. |
| Gain: |
A measure of amplification, usually expressed in dB. For match CATV components, power gain is readily determined as insertion power gain. The amount of amplification of input to output power often expressed as a multiplicative factor or in decibels. |
| Gain Compression: |
The gain of any amplifier is a function of the input signal level, and will always decrease at some point where the input level is sufficiently high. The capacity of an amplifier is sometimes expressed as the level where the gain of the amplifier is decreased or compressed by a certain amount. |
| Ghosts: |
A ghost displaced to the left of the primary image is designated as "leading", and one displaced to the right is designated as "following" (lagging). When the tonal variations of the ghost are the same as those of the primary image, it is designated as "positive" and when the reverse condition occurs, it is designated as "negative". |
| GHz: |
A frequency designation. Giga means billion and hertz means cycles per second. 3.7Ghz would be 3,700,000,000 cycles per second. 1000 MHz or one billion cycles per second. |
| Ground Loop: |
These humbars are created when there is a substantial difference in the grounding resistance at two different points of a system. Headend : The electronic reception and distribution equipment located at the start of a cable system. The portion of a TV system where all desired signals are received and processed for subsequent distribution. |
| Hertz: |
An abbreviation for the frequency measurement of one cycle per second. Named after Heinrich Hertz, the German scientist who first described the properties of radio waves. |
| Hi-band: |
The VHF television channels. High Definition Television (HDTV) : An innovative television format having approximately twice the number of scan lines in order to improve picture resolution and viewing quality. |
| Horizontal (Hum) Bars: |
Relatively broad horizontal bars, alternately black and white, which extend over the entire picture. They may be stationary or may move up and down. Sometimes referred to as a "venetian blind" effect, it is usually caused by a 60Hz interfering frequency or a harmonic frequency. |
| House Drop: |
The coaxial cable from line tap to participants TV converter. |
| Hum Bars: |
A form of interference seen as horizontal bars or black regions passing across the field of a television screen. |
| I.F.: |
Stands for intermediate frequency. A frequency obtained by a satellite receiver after down conversion. In a dual conversion receiver there will be (2) I.F. frequencies. One is created by mixing the incoming signal with a frequency from the V.T.O. (voltage tuned oscillator). The first I.F. is usually between 500 Mhz and 1.5 Ghz. The second I.F. (70mhz) is created by mixing the first I.F. with impedance is usually 75ohms. |
| Insertion Loss: |
Additional loss in a system when a device such as a directional coupler is inserted; equal to the difference in signal level between input and output of such device. The amount of signal energy lost when a device is inserted into a communication line. Also known as "feed through" loss. |
| Interference: |
An undesired signal intercepted by frequency that causes video and/or audio distortion. |
| Intermodulation (Beat Frequencies): |
A form of interference that is generated from creation of two or more beats between carrier. Beat frequencies are given by fbeat-nf1 + mf2 where n and m are integers. |
| Isolation: |
The amount of separation or loss (expressed in dB) between two locations or components. (Such as the loss between the feed-thru and tap/drop line of a tapoff unit). |
| Isolation Loss: |
The amount of signal energy lost between two ports of a device. An example is the loss between the feed through port and the tap/drop of a top-off device. |
| Isolator: |
A device that allows signals to pass unobstructed in one direction but which attenuates their strength in the reverse direction. |
| Jumper: |
A short piece of transmission line used to interface components in a broadcast system. |
