I’ve always wanted to model the effects of a choke balun on a balanced dipole antenna fed by an unbalanced coaxial feed line. In particular, I wanted to model the antenna and feed system using EM software in order to visualize the electric field and current along the conductors in the system. Essentially, I wanted to prove to myself that the concepts that I’ve seen in literature and...
Digital data can be transmitted wirelessly over an analog channel in various ways. Let’s start with an explanation of digital data. Digital data in modern information systems is also known as binary data, which is represented by a string of “binary” digits (bits), each of which can only have one of two values, either 0 or 1. Sequencies of digital bits can be organized into...
The matched filter is one of the most useful tools available to the Digital Signal Processing (DSP) engineer. Matched filtering maximizes the Signal to Noise Ratio (SNR) of the filter output when a signal matching a known pattern is passed through it. This process is extremely useful for “finding” signal patterns, possibly hidden within a noisy signal (low SNR). One application is in...
The 8-bit Z80 microprocessor has been a popular choice for early computer designs and continues to see some use in embedded systems today. When I was 14 years old, my Dad purchased a Commodore 128 as an upgrade to our C64, which contained both a 6510 and a Z80 microprocessor. In the 128, it was intended to be used as a platform to run CP/M, an OS intended for business computing, which the C128...
In December 1982, Santa delivered a Commodore 64, which became an obsession for me during my childhood and teen years. I quickly discovered that most of the graphic operations I wanted to perform were not possible using the BASIC interpreter built into the OS. Fast, smooth animations were only possible using assembly language routines either natively run or called from BASIC programs. I...
This is a continuation of a previous post in which I examined the signal characteristics of a non-branded dog training collar. I purchased an additional training collar which has two functions: warning, and shock. Our 5 year old lab mix has a dangerous habit of chasing vehicles, and I wanted to curb his behavior as well as keep him safe if he bolted from our front door or gate. With the same...
I picked up a remote control training collar for our 7 year old Maltese to help train her in order to curb barking. In the spirit of keeping everything humane, we only use two of the three functions (alarm, vibrate, and shock), avoiding the shock function for obvious reasons. I became interested in the modulation used to encode the functions, so I used my Real Time Spectrum Analyzer to analyze...