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Archives November 2021

Digital Signal Processing

What is a Digital Signal Processing System?
  • Let’s start with the individual meaning of the words defining Digital Signal Processing in its entirety.
    • Digital: In digital communication, we use discrete signals to represent data using binary numbers.
    • Signal: A signal is anything that carries some information. It’s a physical quantity that conveys data and varies with time, space, or any other independent variable. It can be in the time/frequency domain. It can be one-dimensional or two-dimensional. Here are all the major types of signals.
    • Processing: The performing of operations on any data in accordance with some protocol or instruction is known as processing.
    • System: A system is a physical entity that is responsible for the processing. It has the necessary hardware to perform the required arithmetic or logical operations on a signal. Here are all the major types of systems.
  • Putting all these together, we can get a definition for DSP.

What is Digital Signal Processing (DSP)?

Digital Signal Processing is the process of representing signals in a discrete mathematical sequence of numbers and analyzing, modifying, and extracting the information contained in the signal by carrying out algorithmic operations and processing on the signal.

Block diagram of a DSP system
Block diagram of a digital signal processing system (DSP)
Block diagram of a digital signal processing system (DSP)
  • The first step is to get an electrical signal. The transducer (in our case, a microphone) converts sound into an electrical signal. You can use any transducer depending upon the case.
  • Once you have an analog electrical signal, we pass it through an operational amplifier (Op-Amp) to condition the analog signal. Basically, we amplify the signal. Or limit it to protect the next stages.
  • The anti-aliasing filter is an essential step in the conversion of analog to a digital signal. It is a low-pass filter. Meaning, it allows frequencies up to a certain threshold to pass. It attenuates all frequencies above this threshold. These unwanted frequencies make it difficult to sample an analog signal.
  • The next stage is a simple analog-to-digital converter (ADC). This unit takes in analog signals and outputs a stream of binary digits.
  • The heart of the system is the digital signal processor. These days we use CMOS chips (even ULSI) to make digital signal processors. In fact, modern processors, like the Cortex M4 have DSP units built inside the SoC. These processor units have high-speed, high data throughputs, and dedicated instruction sets.
  • The next stages are sort of the opposite of the stages preceding the digital signal processor.
  • The digital-to-analog converter does what its name implies. It’s necessary for the slew rate of the DAC to match the acquisition rate of the ADC.
  • The smoothing filter is another low-pass filter that smoothes the output by removing unwanted high-frequency components.
  • The last op-amp is just an amplifier.
  • The output transducer is a speaker in our case. You can use anything else according to your requirements.

Applications of a Digital signal processing system

We use digital signal processing in:

  • Telecommunication
    • For echo cancellation.
    • Equalization – Think about tuning your radio for bass and treble).
    • Filtering – Removing unwanted signals using specially designed filters like the Infinite Impulse Response  Filter (IIR).
    • Multiplexing and repeating signals.
  • Instrumentation and Control
    • In designing Phase Locked Logic (PLL).
    • Noise reduction circuits.
    • Compression of signals.
    • Function generators.
  • Digital Image Processing
  • Speech Processing
    • Digital audio synthesis.
    • Speech recognition and analysis.
  • Medicine
    • X-rays, ECGs, EEGs.
  • Signal filtering
    • Noise removal and shaping of signal spectrums.
  • Military
  • Consumer electronics
    • Music players
    • Professional music turntables (like the ones DJs use).

Advantages of a Digital Signal Processing system

A digital signal processing system enjoys many benefits over an analog signal processing system. Some of these advantages are briefly outlined below:

  • Less overall noise
    • Since the signals are digital and inherently possess a low probability of getting mixed with unwanted signals, the entire system benefits. Thus, DSPs don’t really have as much noise to deal with comparatively.
  • Error detection and correction is possible in DSPs
    • Again, the presence of digital signal means we have access to many error detection and correction features. For example, we can use parity generation and correction as a detection and correction tool.
  • Data storage is easier
    • Yet again, an advantage because of digital signals. You know how easy it is to store digital data, right? We can choose from a wide plethora of digital memories. However, analog data needs to be stored in tapes and stuff like that. It’s harder to transport and recreate with 100% fidelity.
  • Encryption
    • Digital signals are easy to encrypt. So this one counts as a win for the entire DSP system too.
  • Easier to process
    • Digital signals can easily undergo mathematical changes as compared to their analog counterparts.
  • More data transmission
    • Time-division multiplexing is a great tool available for digital systems to transmit more data over unit time and over a single communication path.
  • Higher component tolerance in DSP
    • The components like resistors, capacitors, and inductors have a certain threshold in terms of temperature. Outside this threshold, as the temperature increases, they might start behaving erratically.
    • These components are not present in a digital system. Moreover, digital systems can increase their accuracy with concepts like floating-point arithmetic.
  • Easier to modify
    • To modify an analog processing system, you need to change components, test, and verify the changes. With digital processing systems, you just need to change a few commands or alter a few lines of code.
  • DSP systems can work on frequencies of a broader range
    • There are some natural frequencies, like seismic frequencies that detect earthquakes. These signals have very low frequencies. Traditional analog signals might not even detect these signals. However, digital signal processing systems are adept at picking up even the tiniest of disturbances and also process them easily.
  • Cost
    • When working at scale, DSPs are cheaper.

Disadvantages of a Digital Signal Processing system
  • Complexity
    • As we saw in the block diagram above, there are a lot of elements preceding and following a Digital Signal Processor. Stuff like filters and converters add to the complexity of a system.
  • Power
    • A digital signal processor is made up of transistors. Transistors consume more power since they are active components. A typical digital signal processor may contain millions of transistors. This increases the power that the system consumes.
  • Learning curve and design time
    • Learning the ins and outs of Digital Signal processing involves a steep learning curve. Setting up digital processing systems thus takes time. And if not pre-equipped with the right knowledge and tools, teams can spend a lot of time in setting up.
  • Loss of information
    • Quantization of data that is below certain Hz causes a loss in data according to the Rate-Distortion Theory.
  • Cost
    • For small systems, DSP is an expensive endeavor. Costing more than necessary.

With the basic knowledge of the concept, you are now ready to dive right into our digital signal processing course.

Reference technobyte

Willamette Valley Mesh Network

Overview

The Willamette Valley Mesh Network provides a local TCP/IP network for all connected users. It is like a highway leading around the region. Services are like the places you visit and allow you to do useful things which support emergency communications: file transfer and document storage, chat, telephony, network monitoring, mapping, and situational awareness.

Some services are available by simply clicking a link on the mesh status web page, and others run as servers such as a NTP time server. Other services may be accessed through client installed apps. We use mostly open source and free software; some software has been written by our mesh users.

An advantage of the mesh system is that these services are distributed throughout the regional coverage area. This offers the advantage of redundancy in the event of a network disruption, such as a local power failure. For example, we have several different installations of the MeshMap installed on different devices operated by users in Linn, Marion, and Yamhill Counties.

WiFi access can be provided to users of the mesh network to Part 15 Computers, Tablets, and Phones at a deployment site. The AREDN documentation has a good section describing services, and gives examples of services that have been deployed by users of the AREDN mesh network.

Current Services Deployed on the Mesh
  • MeshMap – a live updating map by KG6WXC showing station locations, services and connections.
  • Mesh Chat – a synchronized chat client and server that runs in all regions. Also allow file transfers.
  • APRS-IS – Local mesh server to handle Mesh APRS Traffic to Global APRS IS network.
  • Winlink – telnet post office and telnet P2P modes allow high speed email for amateur radio users.
  • Web servers – Apache and NGINX web servers provide a variety of services using clickable links
  • File Management – Tiny File Manager and FileGator are web file servers for all media.
  • NextCloud – A completely integrated, mesh-hosted content collaboration platform.
  • FreePBX – VoIP telephony provides trunked mesh phones and Linphone cell phone connectivity
  • iPerfSpeed – Utility to test RF connection throughput and packet loss built into the AREDN devices.
  • TeamTalk 5 – A video conferencing client/server (similar to Zoom) for presentations and meetings.
  • Weather Stations – WeeWX and DIY weather stations are installed in Albany and Florence
  • DokuWiki – a collaborative reference document platform
  • DMR Reflector – DMR Reflector to link DMR repeaters and Hotspots overmesh, it also supports linking into bandmister.
  • Rocket.Chat – a communications platform  that offers chat, audio, and video messaging and file transfer.
  • Video – network IP cameras are installed for RTSP video monitoring and viewing in web browsers
  • Wikipedia – The full Wikipedia is mirrored on the mesh, Every article.
  • Othernet – a satellite-based receiver downloads  reference materials and information.
  • Zenmap – a GUI based network topology and monitoring service.
  • Chronyd and NTPd – GPS synchronized local network time protocol services.
  • Arednsig – a custom RF station connectivity monitor written by KA7JLO
  • DIY Radiation Monitor – a custom KA7JLO radiation monitor which can be accessed via web server

Reference – For complete details visit Willamette Valley Mesh Network website.

Station Grounding for Amateur Radio

The word “grounding” — meaning a connection to the Earth — is casually applied to so many different purposes in Amateur Radio, it’s no wonder there are many opinions and misconceptions about it. “Bonding” is a less familiar term to most amateurs. In the electrical sense, bonding simply means “to connect together” so that voltage differences between pieces of equipment are minimized.


Why Are Grounding and Bonding Important?

There are three needs we are trying to satisfy:

• AC safety: protect against shock hazards from ac-powered equipment by providing a safe path for current when a fault occurs in wiring or insulation.

• Lightning protection: keep all equipment at the same voltage during transients and surges from lightning and dissipate the lightning’s charge in the Earth, routing it away from equipment.

• RF management: prevent unwanted RF currents and voltages from disrupting the normal functions of equipment (also known as RF interference or RFI).


Why Is “Grounding” So Complicated?

The very word — grounding — means a lot of different things depending on who you’re talking to and what you’re talking about. Isn’t grounding just connecting equipment to the Earth? That is certainly one definition of grounding.

The British use the terms “earthing” and “protective earth conductor” which are more exact references to what the connection is for. But the layer of soil and rock at the Earth’s surface is not a magic zero-voltage point into which we can pour any amount of electric charge where it safely disappears! The current’s strength and frequency, soil characteristics, whether it is wet or dry, the length of the path to the Earth connection and through the soil — all of these affect what our equipment experiences at the “ground” connection.


Station Grounding for Amateur Radio – Ask Dave

FCC Application Fees Unlikely to Go into Effect Until 2022

From the ARRL: 8/17/21:

The schedule of FCC amateur radio application fees likely will not go into effect before 2022. FCC staff confirmed during a recent virtual meeting with Volunteer Examiner Coordinators (VECs) that the agency is still working on the necessary changes to the Universal Licensing System (ULS) software and other processes and procedures that must be in place before it starts collecting fees from amateur
applicants. Earlier this year, the FCC said it would not start collecting fees from amateur applicants before this Summer. The new estimate is that the fees won’t go into effect until early next year.

Once it’s effective, the $35 application fee will apply to new, modification (upgrade and sequential call sign change), renewal, and vanity call sign applications. All fees will be per application. Administrative update applications, such as those to change a licensee’s name, mailing, or email address, will be exempt from
fees. ARRL VEC manager Maria Somma, AB1FM, said Volunteer Examiner (VE) teams will not face the burden of collecting the $35 fee.

“Once the FCC application fee takes effect, new and upgrade applicants will pay the exam session fee to the VE team as usual, but they’ll pay the $35 application fee directly to the FCC using the FCC Pay Fees system,” she explained. When the FCC receives theexamination information from the VEC, it will email a link with
payment instructions to each successful candidate who then will have 10 days from the date of the email to pay.

The FCC Pay Fees system can be accessed at, https://apps2.fcc.gov/Batch_Filer/login.cfm .

After the fee is paid and the FCC has processed an application, examinees will receive a second email from the FCC with a link to their official license. The link will be good for 30 days. Licensees also will be able to view, download, and print official license copies by logging into their FCC ULS account. The FCC no longer
provides printed licenses.

Licensees can log into the ULS with their 10-digit FRN (FCC Registration Number) and password at any time to view and manage their license and application, print their license, and update anything in their FCC license record, including adding an email address.

FEE SCHEDULE:

INDIVIDUALS –

$35 FEE: New, modification (upgrade and sequential call sign change), renewal, and vanity call sign applications. All fees will be per application.

NO FEE: Administrative updates, such as a change of name, mailing or email address, or license cancellation.

AMATEUR RADIO CLUBS –

$35 FEE: New, renewal, trustee change, and vanity call sign applications. All fees will be per application.

NO FEE: Administrative updates, such as a change of name, mailing or email address, or license cancellation.
NNNN
/EX


ARRL Northwestern Division
Director: Michael T Ritz, W7VO
w7vo@arrl.org

Public Alerts

Emergency Alerts Can Keep You Safe.

PublicAlerts sends information about how to stay safe during an emergency. It can send messages by text, email, or voice message.

It’s available for anyone who lives, works, or visits the Portland-Vancouver Region.

Each county uses a separate PublicAlerts system. Click on the map or enter your address in the box. This will take you to your county’s registration site.

You can also find direct weblinks to the county registration websites on the map.

This system will only send alerts to the email addresses and phone numbers you provide when registering. If you live, work, and play in multiple counties, sign up in each county’s system.

Personal information is kept secure and private. The service is free, but message and data rates may apply depending on your phone provider.

Sign up for PublicAlerts

C4 FM Digital Radio

What is C4 FM

The introduction of C4FM / FDMA technology is the beginning of a new digital communication system in Amateur Radio world. The most attractive advantage of digital communication is the ability to transfer large amounts of data. The 12.5 kHz channel spacing in using the C4FM FDMA digital modulation mode allows high-speed data communication with reliable voice communication and strong error correction performance.

C4FM FDMA offers a 9.6 kbps data transfer rate speed. It differs significantly from existing digital radio systems and expands the possibilities for interesting amateur radio activities in the future.

The C4FM / FDMA technology provides three digital modes and an analog mode (FM) V / D-mode voice and data communication in the same time frame. This mode allows voice data with GPS position data and the ID data to be sent in the same time frame. In addition, transmitting the voice data with strong error correction data, this mode that contributes to the stabilization of the digital communication. This mode is the basic mode of C4FM FDMA Digital HAM radio system.

Data FR mode uses the full data rate of capacity for the Transmission of data. This mode allows you to transfer large amounts of data, text messages, pictures and voice notes data at twice the speed as the V / D-mode. Voice-FR mode uses the full data rate of capacity for voice data. This mode allows a clear high quality voice data transmission.

Analog FM mode is the same as the current FM mode used by all
VHF / UHF amateur radio operators . A very useful Automatic Mode Select function identifies and selects These four modes automatically upon receipt of the respective signal.

Source Reference
http://www.on0dp.be/?page_id=266


System Fusion – Mostly referred to as Fusion is the newest digital radio mode. It was designed by Yaesu and is not an open standard. Yaesu is the only manufacturer of radios for this mode. Yaesu repeaters are true multi-mode capable and can replace an existing analog repeater while still providing digital capabilities.

I monitor 443.050 (locally), which connects me Worldwide to Americas Link.

I run a Yaesu FT70D handheld radio, I can hook it up to an outdoor antenna if needed. Works great!

Useful Links & Videos

Yaesuhttp://www.yaesu.com/

Amateur Radio Hotspots
https://amateurradionotes.com/hotspots.htm

Yaesu System Fusion Introduction

Get Licensed – Learn About Amateur Radio

Before you can get on the air, you need to be licensed and know the rules to operate legally.

Find a Class: Find a license class offered in your local area.

Take Practice Exams: Get a feel for how the exam is going to go and what you should really focus on while studying.

New Hams Info website – NewHams.info site. Its purpose is to provide training, information and general encouragement to new or prospective amateur radio operators (hams). Sort of a virtual “Elmer”, as we say. Experienced hams should find it interesting and useful as well.

Amateur radio – a 21st Century hobby

Whether you enjoy writing software, getting hands-on with practical equipment, developing new technology or simply want to use what’s already there to communicate with others across the world, you’ll find all of this – and more – within amateur radio.

Look Up A Newly Obtained or Current Amateur Radio License. The first place your new license will appear online, please check, Universal Licensing System.

Oregon Hamwan Gets $88,000 GRANT

The Oregon HamWAN program has received an ARDC grant of $88,000 to expand its digital communications network.

The project aims to enhance amateur radio digital and emergency communications capabilities between Portland and Salem, Oregon.

The nonprofit plans to expand its digital communications network by deploying 12 network backbone distribution sites between the two cities. Eventually, the sites will connect to the Puget Sound Data Ring, which currently extends from Seattle to Vancouver, Washington.

The network would allow emergency management personnel to communicate in the event of a disaster, such as a major earthquake, that disrupts telecommunications systems.

In such cases, amateur radio operators will be able to quickly set up network nodes where they are needed to provide emergency communication via the Oregon HamWAN digital network.

ARDC is a California-based private foundation that supports innovative amateur radio projects. The foundation makes grants for projects and organizations that follow amateur radio’s practice and tradition of technical experimentation in both amateur radio and digital communication science.


Press Release



For complete set up and configuration details visit Oregon HamWan Website


Ham Radio Hobbyists Ready for Major Quake

Vietnam veteran Skip Fedanzo shows off the disaster response radio system in his Corte Madera home. Brontë Wittpenn / The Chronicle

Fedanzo is part of a civilian disaster response network relying on early 20th century technology. Alvin A.H. Jornada / Special to The Chronicle

Members of the Radio Communications Volunteers group gather with ham radio antennas for an emergency response exercise in San Rafael. Photos by Alvin A.H. Jornada / Special to The Chronicle

The group believes more primitive technology would be vital if cell phone towers and the internet go down.

At 10 a.m. on Wednesday, Skip Fedanzo was expecting an 8.0 earthquake on the Hayward Fault. Assuming his Corte Madera home didn’t slide down Ring Mountain, Fedanzo was set to make his way past his cell phone, laptop and land-line, heading to his garage for the only communication method he can count on to be still working — a ham radio.

Setting up in his rocking chair, at a window with a view stretching from Mount Tamalpais to the bay, Fedanzo’s plan had him pushing the power button to announce: “This is Skip, KJ6ARL; is anybody out there?” That is the call to bring a response from any or all of 15 ham operators spread from Novato to Point Reyes Station — and Operation Golden Eagle, an orchestrated region-wide emergency response exercise, will be on the air.

The simulation involves five Bay Area counties, where emergency service professionals exchange requests for information and resources after the presumed disaster. But only Marin among the five counties is operating without internet or cell phone capabilities. Instead, Marin is employing a network of amateur radio hobbyists who call themselves Radio Communications Volunteers. Acting under supervision of the Marin County Department of Public Works, RCV is providing vital communications between the emergency operations center and community-based organizations that serve the most vulnerable residents.

The goal is to have the county Board of Supervisors certify RCV as part of its official emergency response. The idea is that early 20th century technology — antenna to antenna, without reliance on cell towers, satellite dishes or cables — will be a vital tool when 21st century technology stops working, which Fedanzo expects to happen the moment the real disaster hits.

“The weak underbelly of America is that we are overly reliant on gadgets and gizmos,” said Fedanzo, 77, a retired software engineer who was trained as a radio operator while serving as a Marine in the Vietnam War. “The more complex the systems get, the more likely they can fail.”

This was made apparent in October 2019 when PG&E activated a five-day public safety power shutdown in Marin County to prevent wildfires from sparking in exceptionally dry, windy conditions.

“They throw the switch and the first thing that goes off is the internet,” said San Rafael ham operator Milt Hyams, 78, a retired county prosecutor who also served in Vietnam, as a captain in the Army Signal Corps. “Then after a few days the batteries in the cell towers started to go out and you couldn’t use cell phones. That was kind of a shock and an epiphany to folks.”

Hyams and Fedanzo both worked that blackout as volunteers with the Emergency Operation Center at the Marin County Sheriff ‘s Office. In the aftermath, they pitched the idea to build a countywide communications network using battery-powered radios and a relay signal atop Mount Tam. That was the start of Radio Communications Volunteers, RCV in the acronym-heavy code employed by ham operators.

In their lingo, RCV provides a service to VOAD (Voluntary Organizations Active in Disaster), which is affiliated with EOC (Emergency Operations Center) in cooperation with RACES/ACS (Radio Amateur Civil Emergency Services/ Auxiliary Communications Services). These are not truckers with clever handles killing time on their CB radios. All 16 RCV operators have been licensed by the Federal Communications Commission and assigned call letters.

“This is KJ6ARL, request radio check,” Fedanzo said on a recent practice day. He was sending a test signal to Hyams, who was parked in his Jeep Wrangler in Fedanzo’s driveway. “This is KM6ASI, checking in,” Hyams responded upon picking up the signal. His Jeep door bears the logo of the Marin Amateur Radio Society with the word “communications” in bold white letters.

Affixed above his left tail light is an antenna as long as the ones used for old-time FM car radios.

“Keeping it simple is our watchword,” said Hyams. “In a real emergency, getting on the air can be as easy as throwing a wire over a tree branch to act as an antenna. Then you don’t need a Jeep.”

RCV is a second response unit, after fire and law enforcement first responders who run a separate radio frequency, Marin Emergency Radio Authority.

“We’re not going to put on Superman suits and go out looking for downed buildings and power lines and put bandages on people,” Fedanzo said. “All of the immediate response will be handled before we get activated. We are mobile telephone booths providing long-haul support.”

For the Wednesday test, Fedanzo was tapped to be the net control operator for RCV, coordinating the hams. Each has been assigned a community-based organization, to which they are expected to carry all of their gear by car, bicycle or on foot, depending on how seriously they envision the scenario of an 8.0 quake to be — 8.0 is more than 10 times the magnitude of Loma Prieta in 1989 and could render roads useless. Once RCV arrives at a site and establishes a pipeline to the emergency operation center, the ham radio guys relay requests for information and resources.

Operation Golden Eagle is a one-day drill. But RCV can go much longer. Fedanzo maintains four days of battery power, plus a portable generator with a 5-gallon gas can to load into his Acura Sedan when he heads down from Ring Mountain and into the disaster zone.

He has not forgotten that after the Loma Prieta quake it took him 20 hours to make it home from Cupertino, 60 miles away. Hyams also has not forgotten his experience of that day, Oct. 17, 1989. He was in the District Attorney’s Office at Marin Civic Center at 5:04 p.m. when “all these law books started falling off the shelves and conking me on the head,” he said. He escaped into a hallway and ran into a county administrator who recruited him on the spot for the Emergency Operations Center.

It took 32 years to get to the RCV, and Hyams is ready for the test. He timed the 15-minute drive to the emergency center north of San Rafael. Once there for the Wednesday drill, he has the dispatch role for hams reporting in from service organizations including Community Action Marin, the Canal Alliance, the San Francisco-Marin County Food Bank and others.

“What Milt and I are doing is using our life experience and radio knowledge to help people communicate when they can’t do it any other way,” Fedanzo said.

Sam Whiting is a San Francisco Chronicle staff writer. Article credits.