64-QAM Archives

2 05, 2012

Why is QAM Getting Me Down?

Mia Colabrese2021-08-18T09:11:04-04:00May 2nd, 2012|

64-QAM lower than Analog video on the downstream? 64-QAM lower than 16-QAM on the upstream? Why is a 6.4 MHz channel lower than a 3.2 MHz DOCSIS channel? Someone said there is math for all of this, but man QAM is getting me down! These questions come up in every lecture I give on DOCSIS. Why do QAM measurements show up at different levels on a spectrum analyzer than analog measurements. What's more, why do QAM signals of different bandwidth have different levels? Some of the questions have

1 03, 2012

Impact of Impulse Noise on Adaptive Pre-Equalization Part II

Mia Colabrese2021-08-18T09:36:31-04:00March 1st, 2012|

In part I of this article I discussed adaptive pre-equalization in DOCSIS cable modems and how it can compensate for many upstream impairments such as frequency response, group delay and micro-reflections. I also left off with a cliff-hanger, which is also the title of the article; impulse noise has an impact on adaptive pre-equalization, but how and what is it? I'll cover both what impulse noise is and why and how it impacts adaptive pre-equalization.

29 02, 2012

Impact of Impulse Noise on Adaptive Pre-Equalization

Mia Colabrese2021-11-24T09:26:04-05:00February 29th, 2012|

For those of you who have attended my seminars you are familiar with adaptive pre-equalization in cable modems (if not I'll explain it in detail momentarily). Also, if you have done any amount of RF plant troubleshooting you are certainly familiar with Impulse noise (again, I'll cover this too). But if you are like me, I never knew that the two topics were co-related.

19 11, 2011

Fresh Tech from Cable-Tec Expo 2011

Mia Colabrese2020-06-09T09:59:13-04:00November 19th, 2011|

At this year's Cable-Tec Expo, Rohde & Schwarz (www.rohde-schwarz.com) introduced a 1U Cable Load Generator (CLG) capable of simulating cable TV networks with full channel loading. This baby is not just limited to North America, but can do channel plans for the World over! Here are the highlights:

2 10, 2009

Speeding Upstream – Part I

Mia Colabrese2021-08-18T10:19:55-04:00October 2nd, 2009|

The first part of this article (in CT's March 2009 issue) discussed downstream potential issues, while this one focuses on the potential issues associated with upstream deployments. In particular, this article covers the critical upstream areas that one should be aware of when getting ready to deploy or already deploying DOCSIS 3.0.