What is … ?
By Ron Hranac
Ours is an industry rich in technology, dating back to the first community antenna television (CATV) systems of the late 1940s to today’s hybrid fiber/coax (HFC) and fiber-to-the-home (FTTH) networks. Underlying all of that technology is a foundational knowledge that in some cases is slowly slipping away, as many of those who understand it have moved on to other industries, retired, or are no longer with us. What can be done to preserve that foundational knowledge?
In the late 1970s to early ’80s timeframe, SCTE offered a series of technical monographs to its members. Each covered a specific topic. (I had several of those monographs in my personal archives until a few years ago, when I donated them to the Syndeo Institute at The Cable Center’s Barco Library.)
Those old technical monographs got me thinking. What if the concept could be resurrected, and a series of new technical monographs created and made available? I ran the idea by members of SCTE’s Network Operations Subcommittee Working Group 1 (NOS WG1), who gave it an enthusiastic thumbs up. The working group completed a project authorization request and submitted it to SCTE’s Engineering Committee for review. The PAR was approved, and NOS WG1 was off to the races, so to speak.
During the past few months, members of NOS WG1 have been writing draft technical monographs that cover a variety of subject matter. As of the end of 2024, six technical monographs have been approved and published on SCTE’s standards download page (https://account.scte.org/standards/library/catalog/).
The technical monographs have been assigned document numbers using the format SCTE 293-n 202x, where n is a sequential number starting with “1”, and “202x” is the year of publication. Figure 1 shows the cover pages of the first six technical monographs.
The good news: There is no cost to download copies of the technical monographs (or any other documents on SCTE’s standards download page), all of which are in the widely used PDF file format. That means they can be easily stored on a computer, printed to provide a hard copy, emailed to others, etc.
Benefits and Target Audience
Early in the development of the new series of technical monographs, members of NOS WG1 discussed who the target audience would be. Given the monographs’ technical content, the hope was that pretty much anyone with a technical background might find the material useful. Each technical monograph provides a high-level overview of its topic, and includes references in the bibliography for those who want more of a deep dive in the subject matter.
Section 1.3 of each technical monograph summarizes the benefits: “The material in this document can be used as part of technical training programs, a tutorial for individuals seeking a high-level understanding of [topic], and/or a refresher for those who may have forgotten some of the fundamentals of the topic.” Section 1.4 of all of the monographs includes the following statement: “The intended audience for this document includes technical personnel from installers to engineers. The material is also suitable for those new to the cable industry.”
The following is a brief summary of each of the currently available technical monographs, along with direct links to each one.
Figure 1. Cover pages of the first six technical monographs.
The foundation of much of the mathematics of cable is the decibel, which is a logarithmic-based expression of the ratio between two values of a physical quantity, typically power or intensity. An understanding of the decibel is important, in large part because of its use as the basis for parameters such as loss (attenuation), gain, signal level, carrier-to-noise ratio, and more. https://account.scte.org/standards/library/catalog/scte-293-1-what-is-the-decibel/
SCTE 293-2 2024,
What is …
Velocity of Propagation?
The performance of coaxial cable is described by several parameters, including one called velocity of propagation (VoP). Velocity of propagation is the speed at which an electromagnetic wave propagates through a medium such as coaxial cable, expressed as a percentage of the speed of light in a vacuum. For instance, a common VoP specification for subscriber drop cable is 85%, which means the RF signals inside of that drop cable are traveling at 85% of the speed of light in a vacuum. This document provides a high-level overview of velocity of propagation and its importance. https://account.scte.org/standards/library/catalog/scte-293-2-what-is-velocity-of-propagation/
SCTE 293-3 2024,
What is …
Return Loss?
There are several ways to characterize impedance mismatches and their severity, many of which are highlighted in this technical monograph. The cable industry has long used return loss, expressed in decibels, which fits in nicely with our use of the decibel for various other measurements. The appendices include discussions about how an impedance mismatch causes a reflection, and the formation of standing waves in a transmission line. https://account.scte.org/standards/library/catalog/scte-293-3what-isreturn-loss/
SCTE 293-4 2024,
What is …
Loss (Attenuation)?
Gain and loss are important but straightforward metrics that have long been used by the cable industry. This technical monograph focuses on loss, what it is, and the importance of managing it in our networks. https://account.scte.org/standards/library/catalog/scte-293-4-what-isloss-attenuation/
SCTE 293-5 2024,
What is …
Unity Gain?
Unity gain is an important concept that applies to the forward and reverse paths of most cable networks. Without it, network performance can be degraded. This technical monograph focuses on unity gain, what it is, and includes examples of downstream and upstream unity gain. https://account.scte.org/standards/library/catalog/scte-293-5-what-isunity-gain/
SCTE 293-6 2024,
What is …
Skin Effect and Skin Depth?
Skin effect and skin depth describe the transmission of alternating current—including radio frequency signals—on and near (below) the surface of a metallic conductor, such as the center conductor and shield of coaxial cable. Skin effect and skin depth are, in part, why signals transmitted in coaxial cable stay inside of that cable (and undesired external signals stay outside of the cable). Skin effect and skin depth are also major factors in the attenuation of coaxial cable varying with frequency. https://account.scte.org/standards/library/catalog/scte-293-6-what-is-skin-effect-and-skin-depth/
Wrapping Up
As of this writing, two more technical monographs have been completed by NOS WG1 and are going through the approval process. They will likely be published on SCTE’s standards download page by the time you read this. The titles of those two documents are “What is … Long Loop Automatic Level Control?” and “What is … S-Parameters?”. NOS WGI is reviewing and editing a working draft of “What is … RF?”, which will also be available soon.
Other topics on the drawing board include frequency response, signal leakage, ingress, field strength, power spectral density, total composite power, noise figure, noise power ratio, carrier-to-noise ratio, impedance, and adaptive equalization. If there is a specific topic that you think NOS WG1 should consider for a future technical monograph, drop me a note at the email address in my bio.
Images provided by author, Shutterstock.
Ron Hranac
Technical Editor,
Broadband Library
rhranac@aol.com
Ron Hranac, a 52 year veteran of the cable industry, has worked on the operator and vendor side during his career. A Fellow Member of SCTE and co-founder and Assistant Board Member of the organization’s Rocky Mountain Chapter, Ron was inducted into the Society’s Hall of Fame in 2010, is a co-recipient of the Chairman’s Award, an SCTE Member of the Year, and is a member of the Cable TV Pioneers Class of ’97. He received the Society’s Excellence in Standards award at Cable-Tec Expo 2016. He was recipient of the European Society for Broadband Professionals’ 2016 Tom Hall Award for Outstanding Services to Broadband Engineering, and was named winner of the 2017 David Hall Award for Best Presentation. He has published hundreds of articles and papers, and has been a speaker at numerous international, national, regional, and local conferences and seminars.
Image provided by author.
Shutterstock
