James O. Farmer

Specifications for tuner design for use in cable ready television receivers and VCRs

It is pointed out that, with the expansion of the number of cable channels from 12 or fewer to the current 78, the realization has come that television tuner performance is not always satisfactory. Some of the performance parameters important to tuners operating on cable systems are described, and tuner performance is compared with set-top converter performance. The following tuner issues affecting performance on cable television systems are discussed: direct pick-up, local oscillator emission, distortion, image rejection, adjacent channel rejection, and noise figure. >

High speed data to the home — An update

This paper describes the current and future practices in delivering video, voice, and data to the home over a single fiber optic strand, a technology known as fiber-to-the-home (FTTH). The topic is of interest to consumer electronics engineers because it represents technology that consumers will be connecting their CE equipment to in coming years. The best-known example of commercial deployment of this technology to date is likely the Verizon FIOS system, but there are others as well. The most fibered countries in the world are probably South Korea and Japan.

Operational Characteristics of Modern Set-Top Terminals

A brief history of set-top converters is presented, along with notation of the techniques commonly employed in modem terminals. The digital architecture of a modern terminal is shown. Key RF characteristics are presented, followed by cursory exploration of one class of scrambling techniques. Finally, some information concerning the compatibility between scrambling and stereo is presented. Most of the material is intended to be generic, but where particular techniques are referred to the system described is that used by the Scientific- Atlanta Series 8500 set-top terminal.

Headend Signal Switching Techniques

Signal switching has been practiced in CATV headends as a means of achieving better utilization of a limited number of channels and for commercial deletion and non duplication substitution. In designing a headend switching system, several problems need to be addressed. A selection can be made between baseband and IF switching, each having advantages under certain conditions. Different types of hardware are available to implement switching operations, including mechanical switches and relays, and electronic switches. When multiple inputs or output are involved in a switching operation, differing methods may be employed to implement signal distribution, with the method selected affecting isolation, loss, and complexity.

Improved Headend Performance Using a Test Demodulator

Besides its traditional applications, a precision demodulator can benefit the CA TV engineer as a tool for improving system performance. In the past, demodulators have been used as inputs to microwave links, and have found use in demod-remod types of headends. In addition to these applications, a demodulator can be of great value during modulator evaluation and set-up, in aligning antennas, and in evaluating headend equipment on an in-service basis

Setting and Maintaining Modulation Levels

We deal here with two related problems faced by the user of television modulators: the problemn of initially setting modulation and the problem of maintaining it over a long period of time. Actually, we have four problems here, because the same problems exist for both audio and video. Failure to maintain correct video modulation may result in loss of sync, a washed out-picture, and weak color in the case of undermodulation. Overmodulation can result in poor detector, amplifier, and kinescope linearity, causing problems with the intensity and tint of picture highlights, and can cause excessive sync buzz in the audio channel. Undermodulation in the audio channel results in weak audio and poor signal to noise ratio. Overmodulation of the audio can result in distortion. Any errors in setting modulation levels are particularly annoying when changing from one channel to another. Signal processors will generally not alter the modulation level of off-air stations, though frequency response errors will cause an apparent change in video modulation depth at higher video frequencies.