Category Archives: Amateur Radio

Ham Radio topics.

Dongle Bits: ADSB Radar and $60 Police Scanner

This article appeared in the The Lake Erie Amateur Radio Association newsletter The Spirit of ’76 and ’88 February 2015 edition and The Wood County Amateur Radio Club newsletter CQ Chatter March 2015 edition.

Read the rest of the series in the Dongle Bits articles category.


The holidays were a busy time at the K8JTK laboratories with a couple RTL-SDR projects. The RTL-SDR is the European TV tuner dongle that was turned into a software defined radio receiver.

Thanksgiving is one of the busiest travel seasons and I wanted to decode ADS-B data to see how many aircraft were flying around. ADS-B stands for Automatic Dependent Surveillance – Broadcast allowing aircraft to be tracked by ground stations and provide situational awareness to nearby aircraft. This is part of the FAA’s NextGen project and mandated by agencies across the globe.

I saw this project in the January 2014 edition of QST written by Robert – W9RAN. He covered building a Collinear Array for the ADS-B frequency of 1090 MHz. I used one of my ham antennas. The RF signal received by the dongle is turned into data packets by a program called ADSB# (included in the SDR# download). VirtualRadar receives those packets, decodes the data, and plots aircraft on Google Maps. This setup can work with a Raspberry Pi and I hope to try this in the future.

adsb-07_browser-06_thanksgiving_travel_and_take_off
Thanksgiving travel in Cleveland, Ohio.

Over the Thanksgiving holiday, I saw 25 aircraft flying around Cleveland on average. I think the most I saw was 48 at once. Not all aircraft have full ADS-B implementations. For example: I would see a call sign but no position data. My receive range (depending on aircraft altitude) was east of Toledo to the PA border and south to Canton. Visit my write-up on this project: ADS-B Decoding with ADSBSharp and VirtualRadar Server.

The second project is a little more complicated but it helped me understand how trunked radio systems work. With the FCC narrowbanding mandate in certain RF spectrum, many public service agencies have decided to “go digital.” In my area the MARCS-IP system and the Greater Cleveland Radio Communications Network are most popular. Both are P25 trunked digital systems. P25 is a specification for voice and data transmission. Trunked radio systems operate by having a radio send data to the control channel requesting communication on a talkgroup. The control channel directs all users of that talkgroup to a specified channel. When the user is done transmitting, all radios switch back to monitoring the control channel for further instructions. This is done seamlessly and allows many users (agencies) to use a small set of radio frequencies. Users only hear the conversations on their assigned talkgroup and not other users on the same system.

dongle-bits-06-p25_trunked_decoding-single_voice_decoder
P25 trunked decoding with a single voice decoder.

Scanners that receive these systems run $500 and go up from there. Using two RTL-SDR dongles and software (mostly free), I’ve been able to receive P25 trunked systems for about $65. One dongle monitors only the control channel and other dongle(s) jump frequencies to receive the digital voice modulation with a program decoding the audio. I can have as many voice receivers as I want whereas a scanner cannot be expanded. Most I’ve heard of is eight. There are some drawbacks like portability. Find out my experiences in my P25 Trunked Tracking post.

Fresh Baked Pi

Raspberry Pi foundation released new models over the last couple months. The biggest news coming at the beginning of February: the Raspberry Pi 2. This model comes with a quad-core CPU and 1GB RAM offering a six times speed improvement, still at $35. Initial reports are it is a lot faster!

Raspberry Pi 2

Along with the new Pi2 came a new version of the Raspbian operating system with optimizations and a new look. In the near future, Microsoft will be releasing a version of Windows 10 Embedded for the Raspberry Pi 2 FREE OF CHARGE! (see the Raspberry Pi 2 link above.)

That’s A Wrap

A goal behind this series has been to expose many hams to newer technologies and younger people to ham radio. These technologies are getting young people interested in experimenting, programming, and even Ham Radio. On podcasts I watch, I’ve heard “I want to get my Ham Radio license” by 20 and 30 year olds like I’ve never heard before. These are young people interested in experimenting, making things, building things, and hacking things — all of which are the foundation of Amateur Radio. Making has evolved into writing software, sending a chip a set of commands and analyzing what is returned, or analyzing packets. Then figuring out “what can I do with this?”

I saw a great technology round-table over the holidays and they talked about getting kids into technology. Many of the methods apply to Ham Radio. As a builder, you build something and presume what will happen. Then something different happens and now you have a mystery to solve. “Why did X happen and not Y?” A new theory develops and sucks you in. This is exactly how the Raspberry Pi, RTL-SDR, and every project surrounding them came to be. It is my opinion that we, as the Amateur Radio community, need to encourage, capitalize, and focus efforts on younger makers and hackers to get them licensed.

As this is my last planned article, I would like to take time and thank the newsletter editors for thinking this series was worth publishing and recreating all the links I included. Thank you to those who told others about this series. I got a ton of feedback and couldn’t be happier that others have found this interesting and sparked them to start experimenting. Most of all, thank you for reading.

My Experiences as a New HF Ham Radio Operator

Updated: 5/29/2018

I’ve been licensed since 1999 and upgraded to General and Extra in 2008 but I hadn’t been on the amateur HF bands very much.  When I graduated from Grad School, I bought myself and setup a new HF station.

This post is going to be about my experiences, things I’ve learned along the way, and maybe some things that may not be obvious to someone starting out.  I will add to this post.

This is not meant to be “all-inclusive” by any means and not meant to be a substitute for elmering and experience.  It’s meant to be for someone who has operated VHF/UHF for a long while but just venturing out into HF.

I’m bitter in alot of this post because many points draw on real interactions I’ve encountered.  It’s not to discourage you to operate HF but to be better than the other guy acting like a jerk.  Common sense helps tremendously.  Folks out there who are all about the points, number of exchanges, getting that last contact, and awards common sense almost always goes out the window.  Just remember you have a choice to not work those stations.

A quick note… ac6v.com has a TON of good information on everything from “antennas to zones.”  I think it could be organized a little better and layout is a little 1996ish, regardless 700 amateur radio topics are covered. The Google search at the top really helps finding things.

Let’s get started.

SSTV Transmissions from the International Space Station – December 2014 edition

I saw a news story on the ARRL website that talked about the Russian International Space Station cosmonauts plan to send Slow Scan TV images around the holidays.  December 18 and December 20, 2014.  Those are two of my interests, SSTV (or digital modes in general) and spaceflight.  From the news story:

The Russian Amateur Radio on the International Space Station (ARISS) team members plan to activate slow-scan television (SSTV) from the ISS on December 18 and December 20. The expected SSTV mode will be PD180 on a frequency of 145.800 MHz with 3-minute off periods between transmissions.

I setup my station to monitor 145.800 MHz on both days to see if I could receive any images, I did!

Station setup: MP Antennas Classic Mobile NMO Antenna – This is a local company in Cleveland and were reviewed in QST.  Been using their antennas for a long time with great success.  Since the antenna is multi-polarized (the MP in the company name), it is supposed to be a good substitution for receiving satellite transmissions without a directional antenna and not worrying about Doppler Shift (which needs to be accounted for in some cases).  The height is about 15 feet.

The antenna was connected to my ICOM IC-7000 with DSP settings turned off on 145.800 MHz FM.  Used this radio only because my SignaLink USB is connected to it and the one I use for digital operation on all bands.  MMSSTV is the Slow-Scan TV program I use.

I have tutorials available to help get your station setup and getting started with MMSSTV to receive images from the ISS.

I received 6 images total including 2 partial images from my location near Cleveland (EN91bl) as the ISS was flying overhead.

SSTV Transmissions from the International Space Station 2014-12-18 1901
2014-12-18 1901 UTC
SSTV Transmissions from the International Space Station 2014-12-18 2037
2014-12-18 2037 UTC
SSTV Transmissions from the International Space Station 2014-12-18 2214
2014-12-18 2214 UTC
SSTV Transmissions from the International Space Station 2014-12-20 1719
2014-12-20 1719 UTC
SSTV Transmissions from the International Space Station 2014-12-20 1854
2014-12-20 1854 UTC
SSTV Transmissions from the International Space Station 2014-12-20 2029
2014-12-20 2029 UTC

Dongle Bits: Settings, Programs, & Apps for Software Defined Radio

This article appeared in the The Lake Erie Amateur Radio Association newsletter The Spirit of ’76 and ’88 October 2014 edition and The Wood County Amateur Radio Club newsletter CQ Chatter November 2014 edition.

Read the rest of the series in the Dongle Bits articles category.


Last time on Dongle Bits, I talked about the $20 European TV tuner dongle that was hacked allowing direct access to the signal data. The result is a cheap wideband receiver for your computer. We’re going to take a look at key settings you should know about when using these devices. Then look at some software and projects that transform these into systems that would have cost hundreds or thousands of dollars!

PPM and Settings

An important thing to know about these dongles: they are cheaply made and not tested for accuracy. They are designed to receive DVB-T signals at a bandwidth of 6 – 8 MHz where a few KHz error doesn’t matter. This is obviously not true when you’re dealing with FM signals that are 16 KHz wide or digital at 12.5 where a few KHz will put you on a completely different frequency or channel.

PPM stands for parts per million and is the difference in received frequency vs. frequency shown. To visualize this, use SDRSharp to receive a known FM signal. The center frequency shown will be different from the signal on the scope. Typical PPM offset is anywhere from 45 – 65 and will be in the programs settings. The dongle will drift another 2 – 5 PPM over the next 20 – 45 minutes as it warms up. Gain is obviously another setting that will help you receive signals. The RTL AGC setting works but will err on the side of too much gain. Manually, using more than 32.8 dB will overload and produce duplicate signal spikes. The Correct IQ setting will get rid of phantom spikes at lower gain settings.

PPM at 0
Dongle with no frequency correction. The actual 162.550 frequency is just to the left of the displayed frequency. 162.550 is one of the NOAA Weather Radio frequencies.
RTL-SDR Settings (PPM corrected)
Shows the gain and PPM frequency correction of 55 for the dongle I’m using.
PPM Corrected
Shows 162.550 centered with frequency correction applied.

The crystals on the RTL-SDR dongle can be replaced with higher accuracy temperature controlled crystals (TCXO) that have a variance of 1 ppm! These crystals are $10 but you have to wait for them to ship from China. Pre-modified dongles are available but you will pay three times the price for the dongle.

Android

PCs aren’t the only place these SDRs can be used. They can be plugged into an Android device too. You will need a USB OTG cable (on-the-go) and Android 3.1 or later. Search Amazon or EBay for “USB OTG.” OTG is a standard for plugging in USB keyboards, mice, and thumb drives into mobile devices. Running external USB devices off the internal battery will drain it much faster. A powered USB hub would off-load the dongle power consumption. Apps include SDR Touch (wideband receiver program), ADSB Receiver, and SDRWeather for monitoring NOAA weather alerts on your device.

IMG_0003
This is the RTL-SDR running on my Android Nexus 7 tablet with SDR Touch receiving the 146.880 repeater in Lakewood, Ohio. It is connected with a USB OTG cable to the RTL-SDR dongle, then to an MCX to SMA, and then SMA to PL259 adapter.
Screenshot_2014-09-25-21-24-12
This is a screenshot of the above setup with SDR Touch.

What can I do with this thing?

The definitive source on all things RTL-SDR is at the appropriately named www.rtl-sdr.com website. This site has it all. They regularly post software, updates, projects, and new developments. There is something new just about every week.

Some features of RTL-STR.com are The Big List Of RTL-SDR Supported Software. This is the list of software packages that support RTL-SDR on all platforms. Software ranges from wideband receivers to single purpose programs. This will give you some ideas of things to try with RTL-SDR. SDRSharp was written to have plugins extend the functionality of the program. These include plugins that make SDRSharp scan frequencies, add an audio FFT, scope, level meter, or CTCSS (PL) detector.

There is an extensive list of projects and write-ups including an Amateur Radio category. Some interesting ones are receiving live NOAA satellite imagery, analyze cellular phone GSM signals, radio astronomy, signal strength heat mapping (foxhunting?), and how Brazil uses our military satellites to transmit SSTV images.

With the onset of many digital standards and narrowbanding, there are more digital signals out there you may not be able to identify by hearing them or seeing them on the waterfall. This Signal Identification Guide has known types, frequencies they may be heard on, mode, bandwidth, sample audio, and waterfall image. I find myself using the Radio Reference database search utilities to help identify signals and their owners (a premium account maybe needed for some features).

My first SDR project was to use the Raspberry Pi as a SDR remote network server. The Raspberry Pi could be placed in an attic or basement connected to an antenna and controlled by another computer.

Audio can be piped from one program into another using Virtual Audio Cable (VAC). Some time ago, during one of the digital nets on the .76 repeater in Cleveland, I used SDRSharp and VAC to receive the FLDIGI messages being passed on the net. The signal path looked like this: received RF signal (146.760) -> RTL-SDR (signal data) -> SDRSharp (audio out) -> Virtual Audio Cable -> FLDIGI (audio in) -> message decoded on screen. If I had a HackRF, I probably would have been able to transmit messages without using any “ham” gear.

The next and probably final article, I will demonstrate tracking airplanes equipped with ADS-B transmitters and listening to trunked P25 public service radio systems for under $100.

Dongle Bits: Projects

This article appeared in the The Lake Erie Amateur Radio Association newsletter The Spirit of ’76 and ’88 June 2014 edition and The Wood County Amateur Radio Club newsletter CQ Chatter July 2014 edition.

Read the rest of the series in the Dongle Bits articles category.


We’re going to take a look at projects others have done with micro-computers and controllers. Many of these will be Amateur Radio related but I will highlight some getting started projects that show setup or basic programming. Since many Hams are into computers and programming, I will highlight some networking and server related uses. Finally, some of the more some crazy and unique setups I’ve come across.

First thing to note: if you receive this newsletter in printed form, you’ll want to go to the club’s website or get it in electronic form to view these links. Links will be to videos or instructions posted online. Any YouTube videos will start at the beginning of the segment.

Getting started tutorials

Ham Radio

I was informed the University of Akron Amateur Radio Club (W8UPD) was planning on using the Raspberry Pi for their second High Altitude Balloon launch on April 8, 2014. Though no reason was given, it was scrapped for the Beaglebone Black board. They configured it to send back Slow-scan TV images overlaid with telemetry information. Unfortunately, the launch was a failure due to high winds and “poorly placed trees.” Upon launch, the payload got snagged and caught in a tree.

I heard from John – N8MDP who setup his Raspberry Pi as a D-STAR hotspot as well. His setup works with the “X-Reflector” system. There are multiple D-STAR reflector systems that co-exist together on the network. His instructions are detailed and the setup is different than mine because different software is needed to access these alternative reflector systems. John installed a webserver on his Pi to control it from the Internet.

Raspberry Pi

Arduino

Networking and server

One of the first projects I saw was how to use the Raspberry Pi as a Home theater PC. This allows you to watch videos, listen to audio, or display photos accessible via the network on a TV.

A Pi can be turned into a home or portable access device used in conferences, competitions, demonstrations, or school project. Some examples are a router, network attached storage (NAS) device, web server, or secure virtual private network (VPN) server. The VPN server uses OpenVPN, an excellent encryption package that offers trust no one (TNO) encryption since you generate the encryption keys.

A useful project is the Raspberry Pi IP address IDer which speaks the IP address if you are operating headless and need to connect to it.

Cool and unique

Want to relive the 8-bit gaming days of the Commodore 64? There is a project called Commodore Pi to create a native Commodore 64 emulator and operating system for the Raspberry Pi.

Build a coffee table gaming rig.

Turn a Raspberry Pi into an FM transmitter.

If you like cheap phones, for $160 you can create your own Raspberry Pi smartphone.

Want to give your dog a treat via email? The Judd Treat Machine will do just that! Send an email to the dog’s email address, it dispenses the treat, snaps a picture, and replies with the picture attached.

The University of Southampton in England created the Raspberry Pi Supercomputer using 64 Raspberry Pi computers. They use a “message passing” system to distribute processing across all 64 devices. His son also helped out by building the rack to hold them out of… Legos!

Raspberry Pi and Lego Supercomputer

Other places for projects and news

Raspberry Pi forums.
Arduino forums.
Slashdot: (Pi) (Arduino).
Lifehacker: (Pi) (Arduino).
Reddit: (Pi) (Arduino).
Podcasts.
Search the Internet!

Next time, we’re going to move on to another type of dongle: the $20 software-defined radio.

Dongle Bits: DVAP Pi Hotspot

This article appeared in the The Lake Erie Amateur Radio Association newsletter The Spirit of ’76 and ’88 April 2014 edition and The Wood County Amateur Radio Club newsletter CQ Chatter May 2014 edition.

Read the rest of the series in the Dongle Bits articles category.


One of the questions I was asked about the Raspberry PI was “why would I want to get one of these?” I can say with absolute certainty: the answer isn’t going to be the same for everyone.  My recommendation is to find a project that really gets you excited!  Go out and do it.  Then do it better.  Make it a learning tool as it was intended.  The hardware, operating system, and many projects are published under the Open Source model.  The concept of Open Source is something that can be freely used, changed, and shared.  This means YOU can download a project and “hack” it yourself.  From there, explore other projects or prototype one of your own!

In my previous article, I mentioned two ways to find projects.  For an initial project, I suggest finding something that has a good amount of detail in the instructions.  This way you won’t be frustrated if they are vague or unclear.  Projects with videos and screen-shots are always helpful for me to visualize what is taking place and I’m able to check my settings with theirs.  On the other hand, if the project doesn’t work, it’s a great opportunity to sharpen troubleshooting skills.

After finding out about the Raspberry Pi and seeing projects appearing in blogs and podcasts, the project that got me excited was the “DVAP Pi Hotspot.”  If you’re on D-STAR, you probably know about a couple dongles that make D-STAR available to you if there is not a repeater nearby.  These dongles traditionally need a PC computer, USB connection, and Internet connection to access the D-STAR network.

The blue box is called the “DV Dongle.”  It is D-STAR in a box.  It uses your computer speakers and microphone for sending and receiving Digital Voice (DV).  This dongle does the encoding and decoding internally.  I don’t know of any Raspberry Pi projects using the DV Dongle yet.  The second is the red box called the “DV Access Point Dongle” or DVAP.  This device has a low power, 10 mW 2m or 440 transceiver that works with a D-STAR radio.  It passes the bits from the Internet & D-STAR network over the air to your D-STAR radio and vice versa.  The radio does the encoding and decoding.  These devices are great for traveling as they can be hooked to a laptop and used in a hotel room to link back to your home repeater or favorite reflector.

I had been hearing about this DVAP Pi Hotspot on D-STAR nets.  Two advantages were the unit was self-contained, making it no longer necessary to keep a desktop computer running with the DVAP connected.  Since the Raspberry Pi draws far less power than a desktop, some were leaving their DVAP Pi running all the time.  The second advantage was it could be easily converted into a mobile setup.

I follow the guys over at AmateurLogic.TV.  They’re the longest running podcast dedicated to Amateur Radio and technology.  In episode 57, Tommy, N5ZNO, did a segment on how he setup his DVAP Pi.  The project seemed easy enough and the setup was just like how I wanted mine to operate: “headless” where the app starts automatically so a video monitor is not required, has SSH (Linux Secure SHell) enabled, and connects to a mobile hotspot.  Soon after seeing the segment, I ordered my Raspberry Pi.

I completed the project and got it up and running in short order.  IMG_0003 Wow!  I was so amazed I got to experiment with this small, but powerful computer and have a portable D-STAR hotspot I can take with me anywhere.  Using a cell phone for the Internet connection, I am limited to the coverage area of my cell phone provider, big red.  Their coverage is very good and I don’t have many disconnects.  I use a portable charging station (fancy word for “battery pack”) as the power source.  The pack has 2 USB ports so I can run the Raspberry Pi and charge my cell phone at the same time.  I’ve also used my 1A micro-USB car charger to power the Raspberry Pi.  If the setup is on a home network, there is no need to worry about cell coverage or a portable power source.

I’ll leave the video tutorial to Tommy.  I did a detailed post on my site that shows, step-by-step, how I set mine up.  It’s a little more advanced than Tommy’s setup but it fixed an issue I was having.

When I booted the Raspberry Pi and tried to link the DVAP to a gateway, I frequently got a “gateway unknown” error message.  This error means the remote D-STAR system doesn’t exist or is offline.  However, neither was the case.  The problem was the DVAP software was not able to authenticate my callsign with the D-STAR authentication servers.  This happened because the WiFi interface wasn’t fully operational before the DVAP software tried to log me in.  I was running into this error enough for it to be frustrating.  Usually a reboot would work, however a few times I had to reboot 3 or 4 times.  I fixed the issue with a Linux shell script (like a DOS batch file) to make sure the Internet was accessible before the DVAP software is started.  Volá, fixed my problem! 🙂

Additionally, I added to the setup by installing VNC.  VNC (Virtual Network Computing) is a way to view and control the graphical desktop of the Raspberry Pi (or any computer) over a network connection.  Since there are SSH and VNC applications for smartphones, I am able to fully control the Raspberry Pi from my phone with it connected to the WiFi hotspot application.

IMG_7746That’s the first project I did with my Raspberry Pi.  I’ve done a couple other projects and see some other ones I would like to try out.  Right now, I mostly use my Raspberry Pi as a DVAP hotspot.

Next time, we’ll take a look at how other hams are using microcomputers in their projects.  If you have any projects using the Raspberry Pi, Arduino, Galileo, BeagleBoard/Bone, or any others, let me know.

DVAP Pi Hotspot

DVAPDongleOne of my interests is digital modes, so I’m a D-STAR fan.  My first project with the Raspberry Pi would be the DVAP Pi Hotspot.  The DVAP normally connects to a computer and has a low power, 10 mW 2m or 440 transceiver that works with a D-STAR radio.  It passes the bits from the Internet & D-STAR network over the air to your D-STAR radio and vice versa.  The radio does the encoding and decoding.

Thanks goes out to the guys over at AmateurLogic.TV.  Tommy, N5ZNO, did a DVAP Pi segment in episode 57 that I used to build mine.

Requirements

Much like Tommy, my DVAP Pi had to be portable (battery operated), headless (no monitor, autostart), use a cellphone WiFi hotspot, and administered through SSH and VNC if needed.  On Windows, I use PuTTY and TightVNC.  On Android, I use JuiceSSH and PocketCloud.

Assumptions

With this tutorial, I’m assuming anyone setting this up is already familiar with D-STAR, registered on the D-STAR network, and familiar with using the DVAP on a PC.

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!

DPRS problem

I was hoping to use the DVAP Pi as a portable DPRS (D-STAR APRS) iGate to report location data to the APRS network.  It currently does not.  It only reports D-PRS data to the gateway system you’re connected to.  No further.  It will show up on the gateway’s DPlus Dashboard but the DVAP Tool nor the gateway/reflector/repeater will not pass location data to the APRS network.

If you come over the RF side of a repeater with a GPS enabled radio, it will pass the location data to the APRS network.  The repeater will not pass location data to the APRS network when transmitting through a DVAP linked to the system.

This is true when the DVAP is connected to a PC or the Pi.

Program versions

I used a Windows 7 64 bit PC. Applications and versions used in this writeup:

  • Wheezy Raspbian 2014-01-07
  • Win32 Disk Imager 0.9
  • PuTTY  0.63
  • TightVNC 2.7.10 64 bit
  • DVAPTool 1.04
  • Mobile Hotspot ? (added after publishing)
  • JuiceSSH ? (added after publishing)
  • PocketCloud ? (added after publishing)

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.

Downloads

01_raspberry_pi_downloads

Go to http://www.raspberrypi.org/downloads and find the “Raw Images” section.

Download the Win32DiskImager and Raspbian image (800 MB).  Save them in your Downloads folder.