Tag Archives: Digital Modes

Amateur Radio, Tutorials

APRS RX IGate with RTL-SDR and Raspberry Pi

For sometime I wanted to experiment with an APRS IGate. Coverage was spotty at best in my area. There is an IGate in my city but it doesn’t receive so well. Recently there have been more IGates blanketing the area.

APRS stands for Automatic Packet Reporting System and has been developed since the late 1980s by Bob Bruninga – WB4APR. It’s a digital communication mode amateur radio operators use to primarily broadcast location information, though this wasn’t the intended use. It handles text messages, alerts, announcements, bulletins, and information of interest like weather station reports. APRS operates typically on a single frequency.  A system of relay stations and digipeaters repeat messages over a wide area. APRS Internet System (APRS-IS) are Internet connected receivers (IGates).

Any ham can add an icon or information to the APRS map.  The information is available on the Internet or to users on the local RF network.  Data is automatically tracked over time. APRS is frequently used to track mobile stations in a public service event or volunteers in a search and rescue event to visualize locations and track progress.

This project will utilize the Raspberry Pi and RTL-SDR dongle. The Raspberry Pi is a credit-card sized micro-computer intended for teaching computer science to students but became popular with the makers. RTL-SDR dongles are DVB-T (European standard) TV tuner dongles. It was found the signal data could be accessed directly which allowed them to be converted into wide band software defined radio receivers. The Pi costs about $35 and RTL-SDR about $20.

Since the RTL-SDR dongles are meant to receive high power wide bandwidth TV signals, they are not as as sensitive or frequency stable as a ham radio or scanner. Receiver performance will be a little less than an equivalent radio performing the same task but depends on the usual variables: amount of APRS activity, antenna height, antenna gain, propagation, etc, etc. With my antenna about 15 feet high, I get about 5+ miles of coverage. With band openings I’ve heard stations on the opposite side of town and across Lake Erie into Canada.

Even though this IGate will be non-transmitting (cannot relay packets from the Internet), packets are forwarded to APRS-IS. The higher profile – higher power Digitpeaters in the area will relay packets received by your IGate to the local RF network.

Assumptions

This guide is step-by-step in nature, meant for beginners, with brief explanations of the steps. It will help to have an understanding of Linux commands and scripting. Capitalization is important in Linux!

My setup is on my home LAN. The IGate could be installed at a remote site using a shared Internet connection. Be aware that firewalls that might block connection to the APRS-IS network on a shared connection. You may want to request or have port 22 open on your router for SSH to establish a remote connection.

If all wired options fall through, look for a cellular hotspot device such as a MiFi to install along with the Pi. Use the built in WiFi on the Pi 3 or approved WiFi dongles for earlier Pi devices. Associate the MiFi with your Pi (turning on WPA2 so no one else piggybacks on your connection). Test the setup before installing it. Don’t find out after leaving the site that the MiFi times out after a few hours.

Program versions

Applications and versions used in this writeup:

  • Windows 10 64 bit
  • Raspbian Jessie 2016-05-27
  • Win32 Disk Imager 0.9.5
  • PuTTY 0.67
  • SDR Sharp 1.0.0.1444
  • RTL-SDR 0.5.3
  • Multimon-NG ?
  • Pymultimonaprs 1.3.0

Parts list

Listed below are all the parts needed to get this project working. It is noted when items can be left out or substituted.

That’s all the parts needed for this project. Check out the AdaFruit Raspberry Pi page for other hardware that might be useful, like the USB to PS/2 adapter for example. Many of these parts are included in the Raspberry Pi Starter Pack.

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Amateur Radio, Digital Communications in Amateur Radio articles

Digital Communications in Amateur Radio: Station Setup

This article appeared in the The Wood County Amateur Radio Club newsletter CQ Chatter May 2016 edition.

Read the rest of the series in the Digital Communications in Amateur Radio articles category.

This time in our quest to get on the air with digital, I’ll discuss station setup. For most of this article, it will be related to HF and sideband operation. I’ll talk about FM near the end.

For a Ham Radio digital setup, three things are needed: a radio, computer, and an interface to connect the two.

First the radio. Theoretically, any radio can be put into digital service. Two things are important to consider: frequency stability and switching speed. Frequency stability is critical to digital operations because drift is deadly. Tube and older radios tend to drift in frequency as they warm up. For a mode such as PSK, drifting a few hertz puts you into someone else’s conversation. Switching speed and fast turnaround times are needed. The switching speed of older radios can be hard on relays. Solid-state radios manufactured in the last two decades are recommended. Radios that cover HF/VHF/UHF all mode – open up even more operating possibilities.

icom_ic-7000_(accessory_&_data_ports)
ICOM IC-7000 rear view showing data and accessory ports.

Most radios are designed with digital modes in mind. Radios with an “accessory port” or “data port” built in are ready to go, though not plug-and-play. The data port is the recommended way to connect an interface to the radio. These ports have pins for keying, transmit audio, and received audio. The audio pins have fixed audio levels and do not change based on the volume setting of the radio. If the radio doesn’t have accessory or data ports, microphone and audio out can be used. It’s not an ideal situation but it will work. An important thing to keep in mind, some radios mix various audio inputs. An example is an external mic connected to the accessory port maybe mixed with audio coming into the data port. This means audio generated by the computer will mix with ambient noise picked up from the microphone. You don’t want this because you’ll interfere with other digital exchanges. It’s important to know your radio and how it operates in different configurations. Test with a buddy or Elmer first before jumping in.

CAT (Computer Aided Transceiver) ports on the radio including RS232 (serial port) and CI-V are useful when creating your own interface. Audio cables between your radio and computer would provide transmit and receive audio but these won’t key the radio. CAT ports provide a lot of functionally including the ability to change settings in the radio, update memory channels, change frequency, etc. Keying the radio via CAT is universally supported in applications. A configuration example would be using the soundcard for audio in/out to the audio out/mic-in on the radio. A separate cable between the computer and radio provides CAT commands, usually via a COM port.

Duty cycle is the amount of time the radio is generating RF. When operating SSB voice, the amount of RF the radio generates depends how loud your voice is at that moment. In CW, RF is generated with each dot and dash. In both cases, the radio is operating at less than 100% duty cycle due to pauses in between words and characters. Many digital modes operate the radio near 100% which causes a lot of heat. Heat causes components to fail. Radios are designed for SSB voice though some newer models are including 100% duty cycle. Operate the radio at a power setting of 50% or less (30% recommended) of the total output power. A 100 watt radio would be set between 30 and 50 watts. FM, by nature, is the exception because voice or digital over FM uses the same bandwidth. The typically longer key down times for digital will still generate more heat.

Radios have different operating modes: USB, LSB, FM, AM, RTTY, DATA, DIGITAL and possibly others. HF digital mostly uses Upper Sideband regardless of frequency. In most cases the USB setting is what you want. Some radios will not allow keying from a computer unless they’re in a ‘digital’ mode setting. Check your operating manual and, again, practice and test with a buddy first. Turn off all filters, blankers, attenuation and the like or set it to the least disruptive setting. Set transmit and receive bandwidths to the full SSB bandwidth allowed (2.8 kHz). No filtering and wide bandwidths have less of a chance to distort or modify the signal. Modification of the signal affects the ability to decode a signal. Filtering can be used but after practice and understanding how they affect decoding. Contests usually warrant filtering to keep loud adjacent signals from affecting the exchange.

The interface. It serves two main purposes: act as a modem and the device that keys the radio. It acts like a modem by taking modulated audio from the software application and sending to the radio for transmit and taking received audio from the radio and sending it to the application for demodulation. Nearly all computers and laptops in the last decade have on-board audio while older configurations utilize an addon soundcard. Most computers don’t have serial ports these days. If a serial port is needed for CAT, options such as a USB (Universal Serial Bus) to serial adapter, serial port addon cards, or cables manufactured with USB to serial adapters built in are available.

rigbaster_advantage
RIGblaster interface–front view.

All-in-one interface solutions make the connection between the radio and computer easy. Solutions offer a built in sound card and fewer cables needed to make the connections. Offerings include products from West Mountain Radio, MFJ, MicroHAM, or RigExpert. These options free your on-board soundcard to listen to music or surf online minimizing the possibility of transmitting audio not suited for the airwaves. Adjustments on these interfaces are audio levels and speed (delay) at which the interfaces switches the radio from transmit to receive. Newer models include all functionality integrated into a single USB port requiring only one cable.

signalink_front
SignaLink USB interface–front view.

The recommended solution for a radio without integrated USB audio is the Tigertronics SignaLink USB. Two cables are needed to make all connections. A USB cable connects the computer and SignaLink for the audio (soundcard) and a cable to the radio for audio and keying. The cable for the radio is specific to connector type or manufacturer. A list of cables is available and simple internal wiring diagram to match the cable to the radio.

signalink_back
SignaLink USB interface–rear view.

Unterminated cables are available to create custom solutions. The SignaLink and cable are about $120 and available at all ham radio retailers. It is a simple VOX (“voice” operated switch) device. When sufficient audio is generated by the computer it keys the radio. It unkeys the radio when that audio has fallen below a threshold.

signalink_diagram
SignaLink USB connection set up.

If you have an interface or are setting one up for the first time, I wrote a tutorial on configuring the interface in Windows. It shows setting default devices and audio levels. These settings help avoid splattering on the bands (taking up more bandwidth than intended) due to too much audio fed into the transmitter. Again, practice with a buddy or Elmer to verify optimal audio settings. Included is a section showing how to record digital transmissions and play them back for decoding at a later time (time shift) such as a net: http://www.k8jtk.org/2015/04/16/radio-interface-setup-for-getting-started-with-ham-radio-sound-card-digital-modes/

The computer. Aside from the requirements to make connections, most computers work fine for digital operation. Ones made within the last decade seem to work without issue. Some older ones tend to have issues. A computer with a 1.5 GHz CPU and 4GB of RAM is sufficient. As always, more is better. Windows is the operating system of choice for digital programs. Mac and Linux are well represented with a program or two less viable than their Windows counterparts. Let’s not forget portable devices like tablets and smartphones. Digital applications are available for those devices too. My operating has been on a Windows 7 64 bit desktop computer.

Up to this point I’ve talked about operating digital on HF and Sideband. What about Technicians who don’t have access to digital portions of the HF bands? All of these digital modes can be operated over FM so you Technicians can get in on the fun too. Won’t be able to transmit as far as an HF station but digital can be transmitted over simplex or even a net on a repeater using an HT! On HF, audio tones are generated by Audio Frequency Shift Keying (AFSK). Audio generated by the computer is converted into RF frequencies when transmitted. Only those frequencies in use at that time are transmitted by the radio. This allows hundreds of exchanges to take place on the same frequency. FM on the other hand occupies the full 10 to 15 kHz, even though the bandwidth of the audio generated by the computer is less. So it still stands only one transmitting station can have the frequency at a time. Yes, this defeats the purpose of narrow bandwidth modes. Someone wanting to learn and experiment with these modes may get bitten by the bug and lead to a license upgrade. I say let them have at it. That’s how I did it.

To this point, Stephen Cass – KB1WNR, Senior Editor for the IEEE magazine built a low power FM digital transmitter for just that reason, get more people interested in digital. It’s a great maker project or demonstration tool for digital. I also mention it because he used my instructions to get Fldigi running on the Raspberry Pi! http://spectrum.ieee.org/geek-life/hands-on/hands-on-a-ham-radio-for-makers

Next time, I’ll start covering specific digital modes, software, and operation.

Images: F8DZY, W3YJ, West Mountain Radio.

Amateur Radio, Tutorials

Calibrate Receive Audio for Ham Radio Soundcard Digital Modes

This tutorial will show to determine an optimal Receive Volume (RX) level on your audio interface for operating (or only receiving) digital modes.  My tutorial showing how to setup your audio interface in Windows is the starting point for this tutorial.  Please review it, specifically the “Recording” settings as this tutorial builds upon it including having an existing audio interface setup.

The audio level from the radio into the audio interface is typically a fixed level.  Once the audio enters the audio interface, the level sent to the computer is adjustable by the RX or Receive Level controls.  This tutorial will help determine the optimal setting for the RX level.

Soundcard Oscilloscope is a program that emulates an oscilloscope from signal data received from a sound card.  The radio will need to monitor active digital transmissions.  Tuning to HF frequencies where PSK31 (7.070/14.070), JT65 (7.076/14.076), or RTTY (7.080-7.125/14.080-14.100) transmissions can be observed are great places.  The 40 and 20 meter frequencies for those are listed as those bands are more active.

This tutorial can help set the transmit level of another station by observing or monitoring their transmissions.  Do this only after you’ve calibrated your receive audio and spent a good amount of time operating with no audio issues of your own.  Use a quiet simplex frequency both can hear the other station.  This way adjustments will not be effected by other stations on the same sideband frequency.  FM won’t matter because only one station can occupy the frequency at a time.

A similar tutorial appeared in QST recently.  They beat me to it, lol!

Program versions

  • Windows 7 – 64 bit
  • Soundcard Oscilloscope 1.46

Download and Installation

This will install Soundcard Oscilloscope on your PC.

receive_level_calibration-01_install-01_soundcard_oscilloscope_website

Go to https://www.zeitnitz.eu/scope_en.

Click the link to “Download the latest version.”  Save it in your Downloads folder.

receive_level_calibration-01_install-02_installer-01

Launch the installer.

Click Yes.

receive_level_calibration-01_install-03_installer-02

Click Next.

receive_level_calibration-01_install-04_installer-03

Click Next.

receive_level_calibration-01_install-05_installer-04

Click Next.

receive_level_calibration-01_install-06_installer-05

Installation will begin.

receive_level_calibration-01_install-07_installer-06

Click OK.

receive_level_calibration-01_install-08_installer-07

Click Finish.

Soundcard Oscilloscope is now installed.

Configuration

This will setup Soundcard Oscilloscope to capture audio coming from your audio interface device.

receive_level_calibration-02_configuration-01_language

Start Soundcard Oscilloscope by clicking the Start orb.

Click All Programs.

Click Scope.

Click Scope.

The first time the program is run, you’ll be prompted to select a language.  Select your language and click Continue.

receive_level_calibration-02_configuration-02_license

The program is not free and will ask for a License key.  Not entering a license will display this screen each time the program is started.  The program is less than $12.50 US.  Please support the developers by purchasing a license.  This is made at the download site by clicking the “private donation license” link.

Click Continue if you don’t have a license.

receive_level_calibration-02_configuration-03_audio_interface_selection

Click the Settings tab.

Under Windows Sound Parameters, Audio Devices, Input is where you select the audio interface device.  For SignaLink USB, this would be Microphone USB Audio Codec.  Other interfaces: Line In, or Mic In would be selected appropriately and known from my audio interface setup tutorial.

Soundcard Oscilloscope is now configured.

Setting receive level audio

These screenshots will help determine optimal audio RX setting for receive audio.  It is important to leave the audio level settings alone in Windows.  These settings were shown in my audio interface setup tutorial.  Adjust the settings in Windows ONLY when where is not enough audio when RX level is at the maximum setting or there is too much audio with RX set to the lowest setting.

receive_level_calibration-03_calibration-01_settings

Click the Oscilloscope tab if you are not there already.

These settings will need to be reset after restarting the program.  At this point, my radio is off but it doesn’t matter.

Set the Amplitude to 250mv.

Set Time to 10ms or less.

Turn on the radio if it is not already.

Examples

Adjust the RX level until there are no peaks with flat-tops on the oscilloscope.  Flat-tops indicate the audio level is too high and digital programs will have a hard time decoding the signal.  These examples were taking monitoring PSK31 on 20 meters.

receive_level_calibration-03_calibration-02_best_example

This is the best example.  No flat-top peaks.  Peaks appear about two divisions from the center line.  There is plenty of headroom for louder signals.  My RX setting was about the 10 o’clock tick-mark on my SignaLink.

Anything lower than two divisions will still work.  There maybe issues pulling out weaker stations.

receive_level_calibration-03_calibration-03_ok_example

Here is a good example but I would not be comfortable with this audio level.  The peaks do not have flat-tops which is good.  However, the peaks are reaching well into the third division.  My RX setting was about the 11 o’clock tick-mark on my SignaLink.

receive_level_calibration-03_calibration-04_bad_example

This is an example of what the scope should not look like.  Peaks have flat-tops at the fourth division.  The audio level is too high into the computer and RX volume needs to be dialed back.  My RX setting was about the 1 o’clock tick-mark on my SignaLink.

When optimal level is reached, the audio interface receive audio level is calibrated!

Amateur Radio, Digital Communications in Amateur Radio articles

Digital Communications in Amateur Radio: Overview

This article appeared in the The Wood County Amateur Radio Club newsletter CQ Chatter February 2016 edition.

Read the rest of the series in the Digital Communications in Amateur Radio articles category.

When I was planning my HF station a few years ago, I knew I wanted to learn more about digital modes. I was familiar with some like Slow Scan TV and Craig – NM8W told me about JT65 a couple years ago. I didn’t understand HF – let alone HF digital. I was lost and had alot to learn.

Since I’ve been on the HF bands, the large majority of my contacts are some form of digital and I’m always exploring new ones. JT65 is my current mode of choice. The perception from many hams is digital modes are foreign and complicated to setup. It takes a little understanding.

In this series of articles, I will be discussing getting on the air with digital from your station. This article will give a general overview of digital communications. Future ones will discuss setting up your station, dive into operating specific modes, and using specific applications. Much of the information will be related to HF and sideband operation. Technicians – fear not, these can be operated on VHF/UHF sideband or even FM simplex with HTs. I’ll get into important distinctions between sideband and FM next time.

I’ve been using computers from a young age. I learned applications and started programming in middle school and continued through high school. I received my undergraduate degree in Information Systems. Through most of college, I was a Technician class licensee and didn’t know much about sideband. I didn’t use computers all that much in ham radio. Most of my activities were related to other things I knew how to do, like build websites. I wasn’t logging or controlling my radio since I was using HTs most of the time.

There were a couple FM digital nets on repeaters in Cleveland that got the ball rolling for me. Slow Scan TV was the first of these modes. It was really cool seeing still pictures come across my screen with a couple audio cables. Later, a digital net for NBEMS training was formed to practice passing messages and forms for emergency communications. That net exposed me to one of the most versatile programs for operating digital modes. After college, I got into D-STAR. That integrated IP (Internet Protocol) technology, which I studied in college, and continued my interest.

Let’s start by taking about digital communications. At a basic level, digital communications is a binary representation and transfer of data (1’s and 0’s). Data is encoded into some structure (protocol, format, rate) before it is transmitted. Digital communication is a very broad term and takes many forms.

Morse Code is the most basic form of digital. The signal is either on or off (1 or 0). The on/off keying creates a series of dots and dashes to make up letters, numbers, and symbols.

Digital voice (often referred to as “DV”) is a method of taking audio from a source (microphone) and digitizing (or encoding) it into a data stream. When decoded at the receiving end, the data stream is converted back into audio and played through a speaker. Voice formats include P25, D-STAR, DMR, FreeDV, and System Fusion. Many voice formats include the ability to transmit a small amount of text at the same time. This text stream is not very fast because voice takes higher priority and the majority of the bandwidth. Text is relegated to call sign, a banner message, or GPS coordinates; things that don’t take a lot of bandwidth.

Data formats exist to transmit text or binary data. Most text based formats are keyboard-to-keyboard or chat style exchanges. Binary exchanges can be files, pictures, or documents. Data format examples are D-STAR, MT-63, MFSFK, JT65/9, Olivia, Packet/APRS, PSK31, RTTY, and System Fusion. Some formats can carry voice (mentioned earlier) but most cannot (i.e. PSK31, RTTY).

Why digital communications? The widespread ownership of personal computing devices allows amateurs to develop and use these modes for communication purposes. Many digital modes are referred to as “sound card modes” because to operate many of them requires little more than a computer, sound card, and radio. In recent years, ‘personal computing devices’ has grown to include smartphones, tablets, and micro-computers because programs have been written to use these modes on those devices.

Digital transmissions can be faster and more reliable. Faster: more words per minute can be transmitted over digital modes. They can be more reliable over greater distances, poorer conditions, and contain error correction. Error correction is the encoding of redundant data into the transmission. When errors are encountered, the redundant information can help reconstruct lost data without retransmission. Error correction helps when noise or other undesirable characteristics are introduced to a receiver. If the signal is completely lost, interrupted, or falls to the noise, no level of error correction will decode the signal. Like most things in technology, each digital mode has its intended use, advantages, and disadvantages. Not all modes fit into all categories and may not be mutually exclusive to a single category.

Next time, I will discuss considerations for your station and the interfaces that go between your computer and radio. Please contact me with questions and ideas. It will let me know what readers are interested in and modes to cover.

Amateur Radio, ARRL Ohio Section, Ohio Section Journal

Ohio Section Journal – The Technical Coordinator – November 2015 edition

One of the responsibilities of the Technical Coordinator in the Ohio Section is to submit something for the Section Journal. The Section Journal covers Amateur Radio related things happening in and around the ARRL Ohio Section. It is published by the Section Manager Scott – N8SY and articles are submitted by cabinet members.

Once my article is published in the Journal, I will also make it available on my site with a link to the published edition.

You can receive the Journal and other Ohio Section news by joining the mailing list Scott has setup. You do not need to be a member of the ARRL, Ohio Section, or even a ham to join the mailing list. Please sign up!

If you are an ARRL member and reside in the Ohio Section, update your mailing preferences to receive Ohio Section news in your inbox.  Those residing outside the section will need to use the mailing list link above.
Updating your ARRL profile will deliver news from the section where you reside (if the leadership chooses to use this method).
Go to www.arrl.org and logon.
Click Edit your Profile.
You will be taken to the Edit Your Profile page. On the first tab Edit Info, verify your Email address is correct.
Click the Edit Email Subscriptions tab.
Check the News and information from your Division Director and Section Manager box.
Click Save.

Now without further ado…

Read the full edition at: http://n8sy2.blogspot.com/2015/11/november-edition-of-ohio-section-journal.html

THE TECHNICAL COORDINATOR
Jeff Kopcak – TC
k8jtk@arrl.net

DSCF5081 K8JTKHey Gang,

During the State Emergency Test (SET), the Medina ARES group had some issues getting Fldigi working correctly. Not because they didn’t know what they were doing but because when you use Fldigi once or twice a year, you forget what to do. I got an email wanting to know if I would develop a training session on NBEMS standards using Flgidi and Flmsg.

NBEMS stands for Narrow Band Emergency Messaging System (or Software, depending who you ask). It is a set of standards developed to define passing email and text-based traffic over Amateur Radio. We have many digital modes available to us. The VHF/UHF standard is MT63. MT63 is a sufficiently robust mode to deal with background noise and poor band conditions. This doesn’t mean you can have a party at your station and still send MT63 messages but it does well with ambient noise. In contrast, HF NBEMS uses Olivia.

This request was right up my alley as I love to operate digital, educate other hams, and help them get on the air. Much of my time this month was dedicated to putting together a presentation covering: digital communication, use case in Emcomm situations, interfacing options, talking about the Fldigi and Flmsg programs used, setting them up, and workflow.

We though this training might be useful to the section so we invited the leadership. Stan N8BHL and Scott N8SY came. There were County Emergency Coordinators (ECs) who were also in attendance. No pressure. We had a lot of people who wanted to learn about NBEMS, Fldigi, and the capabilities we have. After the presentation, we did hands-on demonstrations with Dave NF8O, Bob K8MD, and Fred K8FH as instructors and transmitting stations so students could see transmitting and receiving all in one place. A lot of great questions and discussion was had. Thank you to the instructors and everyone for coming out! The presentation is available: http://www.k8jtk.org/2015/11/10/vhfuhf-nbems-an-introduction-using-fldigi-and-flmsg-presentations/.

DoboyOne of my points during the presentation was always practice with these technologies BEFORE you need use them. Do a class for beginners. Have the students bring their setup –laptops, go-boxes, radio interfaces, and radios. Find some space to hold the class –EOC/EMA building, restaurant, or library. Then walk through the whole nine yards –installing the applications, setting up Windows audio, setting up the applications, and demonstrate the various tasks they would need to perform. Additional instructors who can assist students or send example transmissions (prepare these ahead of time) should be available. Have the students participate by transmitting messages. This will get them more comfortable and it’s easier to troubleshoot on-site than over-the-air. Make plans for some on-the-air meetings to practice ahead of a test or drill. Meet for an hour or so for a couple weeks until everyone is comfortable.

In Cleveland on Thursday nights, I assist with the LEARA Digital Practice Net on the 146.880/R at 9PM (you don’t have to be a member to participate). The net will operate Fldigi for a number of weeks and switch to SSTV for a time. Our net even ran a simulation drill with ICS forms and everything! Turned out to be a HUGE hit. I wrote up some tutorials for our net. They include: getting your radio interface setup with optimal settings, how to use MMSSTV, Fldigi, Flmsg, and Flwrap. The Fldigi suite tutorials are mostly written to FM NBEMS standards. Links are at the end of this article.

signalinkThe OHDEN (Ohio Digital Emergency Net) is on Tuesdays at 8:00pm. 3.585 USB. The net uses OLIVIA 8/500 with PSK31 as an alternate. They do not run voice on this net which might be unusual for some. All checkins and announcements are done using Olivia. More info: www.ohden.org

I encourage groups throughout the Section to start their own digital practice nets on FM, HF, or both! The tutorials are available to modify to fit your net. These are great opportunities to help hams become familiar and knowledgeable about their digital equipment. Do make sure you obtain permission from the repeater Trustee if you plan to use any repeater. If you do have a digital practice net that originates from the Ohio Section, let me know and I’ll put plug in the future.

Earlier, I mentioned Bob K8MD. Bob is the latest addition to the Technical Specialists. Welcome! He has a lot of experience with networking and has been utilizing MESH. Ottawa County is certainly aware of this as he helped their EMA build out a VOIP (Voice over Internet Protocol) system to use during their incidents.

Tutorials:
Sound card setup: http://www.k8jtk.org/2015/04/16/radio-interface-setup-for-getting-started-with-ham-radio-sound-card-digital-modes/

Fldigi, Flmsg, Flwrap: http://www.k8jtk.org/2015/04/16/getting-started-with-fldigi-including-flmsg-and-flwrap/

MMSSTV: http://www.k8jtk.org/2015/04/16/getting-started-with-mmsstv/

Thanks for reading

73… de Jeff – K8JTK

Amateur Radio, Archive, Tutorials

NBEMS/FLDIGI Sound Card Calibration

9/26/2017 update: This is a less effective way of calibrating Fldigi.

The officially recommended calibration method is to use a time standard such as WWV and WWVB.  Details are in the Fldigi manual.

I’ll update or create a post as time permits with more details.  This post and instructions below will be left for reference and should be considered archived.

Archived from: pa-sitrep [dot] com

Archive reason: domain expired, server shutdown, or otherwise unaccessible.

Notes: I had a copy of both the program and the text, I am re-posting both.  Unfortunately it only is available for Windows.

Check the Fldigi tag for my posts running it on the Raspberry Pi or how to use Fldigi.

If you’re concerned about downloading the exe, it was analyzed by VirusTotal and showed 0 detections. The hashes are below and the SHA256 can be compared against the VirusTotal link.

SHA1

396A6ADB43BC76CB48E72A532B2E2E8FE9834551

396a6adb43bc76cb48e72a532b2e2e8fe9834551

SHA256

EE8BA2B907CBCF2551899808ECF717BE61CA76971499CD9EF63F53413114F494

ee8ba2b907cbcf2551899808ecf717be61ca76971499cd9ef63f53413114f494

I do not take any credit for the content or make any claim of accuracy.

1) Download and save CheckSR.exe to your desktop. This is a small, standalone, application that consist of a single exe file. When you double click on it, once it’s saved to your desktop, it provides the capability of analyzing your sound card offsets and gives you the corrections in parts per million (ppm):

http://www.k8jtk.org/drive/ham_radio/digital_modes/checksr/CheckSR.exe

checksr-01-fldigi_audio_devices

2) Open NBEMS/FLDIGI, go to configure, defaults, sound card, audio devices tab and make sure you have the sound card you use for your interface properly selected from the capture and playback drop down choices. Then click the audio settings tab.

checksr-02-fldigi_audio_settings_native

3) Under the audio settings tab, you should see a sample rate drop down box for capture and playback. Under each drop down box, select the sample rate that has (native) listed after it and take note of this figure. Click save config, then click save. Close FLDIGI.

Note: the ‘capture’ sample rate is the only one that seems to have the ‘native’ designation. The playback and capture should be the same.

checksr-04-checksr_input_output_sample_rate

4) Going back to CheckSR, open the application (if it’s not already open, double click on the desktop icon now) and from the drop down boxes for sound card settings, Input and Output, choose the sound card you are using with FLDIGI. Next, select the sample rate from the drop down box in CheckSR for the sample rate that FLDIGI showed as “Native” then click start.

checksr-05-checksr_stop

5) Let the application run for about 15-20 minutes. You will notice that the numbers will progressively stabilize. After about 15-20 minutes, click stop then write down the resulting figures on input and output for the measurements in Hz and PPM. Keep this record.

checksr-06-fldigi_audio_devices_corrections

6) Open FLDIGI, go to configure, defaults, sound card and click on the audio settings tab. Enter the PPM figures for RX ppm (CheckSR ppm Input figure) and TX ppm (CheckSR ppm Output figure). If you had a figure that resulted in a minus from CheckSR, enter the PPM setting with the minus symbol followed directly by the figure with no space. Then click save config, then close.

Although this procedure does not seem to be necessary for MT63 2k long on FM, it is advisable that anyone using FLDIGI, regardless of modes used, should perform this procedure immediately following setup. Once these calibrations are applied to the software, no changes should ever have to be made again, unless you change your software to radio interface sound card.

Amateur Radio, Tutorials

Running Fldigi Flmsg and Flwrap on the Raspberry Pi 2

With the popularity of the Raspberry Pi and the growing need of NBEMS, I wondered if it was possible to run NBEMS programs on the Pi. This maybe of interest to those who want to make a Go Kit (box) with digital or a club wants to replace older computers in their operations center with more efficient devices.

Fldigi is the program used and developed for Narrow Band Emergency Messaging System, but it does so much more. It’s also the standard for many Ham Radio operators because of the number of modes the software will operate.

Fldigi stands for Fast Light Digital modem application created by W1HKJ (David Freese, Jr.) and associates. Flmsg is a forms manager with standardized forms like MARS, plaintext messages, Radiograms, Red Cross, and Weather report forms. Flwrap is a file encapsulation and compression tool allowing for reception of a file exactly like the original.

The Fldigi application is open source, public license software meaning it’s free and available for auditing. With the source code available for Linux, I wondered if it was possible to compile the application on the Raspberry Pi.

At first I had some problems with the project. After (wasting) alot of time on it, I had given up. Only to find out the power supply I had been using was the cause of the issues.

Requirements

Work with my SignaLink USB. As a standard with my projects, the Pi can administered through SSH and VNC if needed. On Windows, I use PuTTY and TightVNC.

Assumptions

This guide is step-by-step in nature, meant for beginners, with brief explanations of the steps. It will help to have an understanding of Linux commands and scripting. Capitalization is important in Linux!

Check my other posts for setup guides on using your radio interface (though written for Windows) and Fldigi, Flmsg, and Flwrap.

Program versions

Applications and versions used in this writeup:

  • Windows 7 64 bit
  • Raspbian Jessie 2015-09-24
  • Win32DiskImager 0.9.5
  • PuTTY 0.65
  • TightVNC 2.7.10 64 bit
  • Fldigi 3.23.04
  • Flmsg 2.0.12
  • Flwrap 1.3.4

Build times

I did a face off for build times between the later model Pi versions: B+, 2, and 3. Later iterations will be faster. The results are in the format of the Linux command time, which contrary to it’s name does not set the time. It gives statistics about this program run. They consist of the elapsed real time between invocation and termination, the user CPU time, and the system CPU time. Later versions than listed above were used in this face off: Raspbian Jessie 2016-05-27, Fldigi 3.23.10, Flmsg 3.0.0, Flwrap is the same at 1.3.4.

Raspberry Pi B+

Failed. Apparently there is an issue running the Make command for Fldigi with versions later than the ones I originally used in this writeup. By the error messages this is an internal g++ compiler error. Make does not fail on the Pi 2 and 3 which probably means it’s a hardware issue (out of memory).

The error is “Warning: partial line at end of file ignored” for dialogs/fldigi-confdialog.o.

Raspberry Pi 2

real 21m49.783s
user 72m9.970s
sys 2m39.290s

Raspberry Pi 3

real 12m50.129s
user 42m8.980s
sys 1m19.160s

Parts list

Listed below are all the parts needed to get this project working. It is noted when items can be left out or substituted.

That’s all the parts needed for this project. Check out the AdaFruit Raspberry Pi page for other hardware that might be useful, like the USB to PS/2 adapter for example. Many of these parts are included in the Raspberry Pi Starter Pack.

If the Pi is setup where there may not be Internet, want to consider purchasing a Real Time Clock (RTC) addon. The Pi will keep time after power has been removed. Of course the time would just have to be set each time.

Flmsg custom forms

In order for custom forms to be used in Flmsg, version 2.0.17 or later must be used. There was a bug in previous versions that didn’t allow the forms to be parsed correctly. In addition, another browser needs to be installed as the default is unable to connect to the webserver created by Flmsg. Thanks to Ken – W0KAH for determining this issue and getting it resolved with the program author.

Linux package installer

The version available from the package manager could be installed but that version is several revisions behind which won’t have the latest enhancements. Some repositories don’t have Flmsg and Flwrap which makes it hard for NBEMS operation.

sudo apt-get -y install fldigi

sudo apt-get -y install flmsg flwrap
If it doesn’t work, you’ll get a message like:

E: Unable to locate package flmsg

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Amateur Radio, ARRL Ohio Section, Ohio Section Journal

Ohio Section Journal – The Technical Coordinator – September 2015 edition

One of the responsibilities of the Technical Coordinator in the Ohio Section is to submit something for the Section Journal.  The Section Journal covers Amateur Radio related things happening in and around the ARRL Ohio Section.  It is published by the Section Manager Scott – N8SY and articles are submitted by cabinet members.

Once my article is published in the Journal, I will also make it available on my site with a link to the published edition.

You can receive the Journal and other Ohio Section news by joining the mailing list Scott has setup.  You do not need to be a member of the ARRL, Ohio Section, or even a ham to join the mailing list.  Please sign up!

If you are an ARRL member and reside in the Ohio Section, update your mailing preferences to receive Ohio Section news in your inbox.  Those residing outside the section will need to use the mailing list link above.
Updating your ARRL profile will deliver news from the section where you reside (if the leadership chooses to use this method).
Go to www.arrl.org and logon.
Click Edit your Profile.
You will be taken to the Edit Your Profile page. On the first tab Edit Info, verify your Email address is correct.
Click the Edit Email Subscriptions tab.
Check the News and information from your Division Director and Section Manager box.
Click Save.

Now without further ado…

Read the full edition at: http://n8sy2.blogspot.com/2015/09/september-edition-of-ohio-section.html

THE TECHNICAL COORDINATOR
Jeff Kopcak – TC
k8jtk@arrl.net

DSCF5081 K8JTKHey Gang.

Normally in this space you would find a well put together article written by Jim W8ERW. If you didn’t catch last month’s Ohio Section Journal, Jim is moving on to bigger and better things. That would be Texas. Jim is one of Fort Worth’s newest residents! The fine folks in the North Texas Section have a great guy coming their way. He’s probably enjoying the warm weather down there right now. Congratulations Jim! So ‘why are we seeing this other guy writing in Jim’s place’ you’re probably asking yourself? I don’t know either.

Seriously though, I have to give a lot of credit to my predecessor, Jim – W8ERW and to our Section Manager, Scott – N8SY. These guys are excellent at answering all my questions from my time as a Technical Specialist and transitioning me into the Technical Coordinator position. Thank you.

I look forward to serving the Ohio Section and seeing what you guys have in store. I’ve already received a number of questions on computers, digital modes, and D-STAR. Happy to answer them. My bio is posted on the Ohio Section website if you missed it.

raspberry-pi-intro-640x420Last month, I gave a presentation on the Raspberry Pi computer at the LEARA meeting in Cleveland. This presentation was an introductory look at the device. It included history, hardware specs, setting up the Pi, and ham radio projects. There was a larger than usual turnout for the meeting and even a few non-hams in attendance. The presentation is available on my website if you would like to take a look. I gave a shortened version at the QCWA Chapter 1 meeting in July. If you missed either meeting, fear not! I am scheduled to be at the GARA (Geauga Co.) club meeting on September 28th as they celebrate 38 years! See you there.
Couple events to note… the Cleveland Hamfest is coming up on September 27th. This is in my backyard so I will be in attendance and hope to meet all of you. You can join the Hamfest Association of Cleveland and help out next year via their website hac.org.

The TAPR Digital Communication Conference is coming up October 9th – 11th near Chicago. Want to go to one of these at some point because it looks like another excellent lineup of forums. Topics include: Digital Voice and Network systems, DATV, Arduino CAT controller for the HPSDR, an Amateur Radio Digital Open Protocol, remote operation of your radio, 3D modeling in Ham Radio, and introductory sessions on a number of topics. ARRL’s own Ward Silver – N0AX is the banquet speaker. Head over to www.tapr.org/dcc.html for the complete schedule and to register.

Thanks to everyone who wrote and congratulated me on my appointment. It really means a lot!
Thank you for reading..

73, K8JTK

Amateur Radio, Tutorials

Getting Started with MMSSTV

Table of Contents

Introduction – page 1

Download and installation – page 2

Configuration – page 3

RX – page 4
-Logging

History – page 5
-Saving images

TX – page 6
-Modes
-Loading images
-Picture clipper
-Transmitting an image from s.pix
-Transmit loaded image

Template editing- page 7

Introduction

This document will demonstrate installation, setup, and basic use of MMSSTV. MMSSTV stands for Makoto Mori (JE3HHT, creator) Slow Scan TV. It has been the defacto standard SSTV application for many years.

This is written with the beginner in mind and many concepts outlined step-by-step. It will provide direction for further experimentation on your own or on the net and direction for troubleshooting.  For SignaLink and audio setup, visit the Radio Interface Setup post.

Prepared for The Lake Erie Amateur Radio Association’s Digital Net (http://www.leara.org/).

Program versions

Program versions used in this document.

Windows 7 – 64 bit
MMSSTV 1.13A – only available on the Windows platform.

Resources

http://en.wikipedia.org/wiki/Slow-scan_television – Wikipedia, history and current systems.

http://hamsoft.ca/pages/mmsstv.php – MMSSTV homepage, sample audio files (to route through the Windows audio system), and help files.

http://www.wb9kmw.com/WB9KMW/sstv_files/tutorial/SSTV_tutorial.pdf – SSTV for beginners. WB9KMW answered some questions with MMSSTV. I’ll plug his introduction. His website has a collection of HF SSTV receivers that can be used to check reception and propagation.

Calibration

Sound card calibration is important in SSTV.  See the “Sound card clock calibration” section in the “Radio Interface Setup – For getting started with Ham Radio Sound Card digital modes” document.  MMSSTV methods: http://www.wb9kmw.com/WB9KMW/sstv_files/tutorial/That_Pesky_Slant.pdf. I prefer this method: http://www.wb9kmw.com/WB9KMW/sstv_files/tutorial/That_Pesky_Slant_WWV_Alternative.pdf.

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