Tag Archives: Raspberry Pi

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

Raspberry Pi – An Introduction to the Credit-Card Sized Computer presentations

I was asked to give a presentation on the Raspberry Pi computer to a number of Amateur Radio clubs in the Cleveland area.

The Technical Coordinator for the Ohio section, Jim – W8ERW, mentioned the presentations in the July 2015 Edition of the Ohio Section Journal.

Framework

The framework I chose to use for the presentation slides is called reveal.js.  It is an HTML framework meaning it will run in any HTML 5 capable browser.  Looks a little better than a PowerPoint presentation.

Navigation

Useful navigation keys in the presentation.  In addition to navigating with the keys below, you can swipe (tables/smartphones) or use the navigation arrows on screen in the lower right.

Toggle full screen: press [F11].

Advance to the next slide: press [n] or [SPACEBAR].

Go back to the previous slide: press [p] or press and hold the [SHIFT] key while pressing the [SPACEBAR].

Display presentation overview: [ESC] then use the arrow keys or mouse to select a slide.  [ESC] again will exit overview mode.

Links

Clickable links are colored in brownish text.

Presentations

Three variations are available: presentation version is viewable in a browser.  Printable version for printing or saving in a different format.  Finally a PDF version.

They may take some time to load because I left original images untouched and some were a couple MB in file size.

Short version

The short version is around 30 minutes in length.

Presentation version
Printable version
PDF version

This presentation was given at the following meetings:
QCWA Cleveland Chapter 1 on 7/11/2015.

Long version

The long version is around 45 minutes in length.

Presentation version
Printable version
PDF version

This presentation was given at the following meetings:
Lake Erie Amateur Radio Association on 8/25/2015.
Geauga Amateur Radio Association on 9/28/2015.
Northern Ohio Amateur Radio Society on 11/16/2015.
Cuyahoga Amateur Radio Society on 9/13/2016.
Parma Radio Club on 12/5/2016.

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.

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: RPi B+ and $20 SDR

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

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


Before we begin talking about the RTL-SDR dongle as promised, some big news broke. The Raspberry Pi Foundation released the Raspberry Pi Model B+. They point out this is not a “Raspberry Pi 2” but an evolution of the model B board. Price is the same at $35. Key improvements are:

  • More GPIO: 40 pins with the first 26 pins the same as the Model B.
  • More USB: 4 USB 2.0 ports with better hotswap and overcurrent behavior.
  • Micro SD: SD card socket has been replaced with a micro SD version.
  • Lower power consumption: Reduced power consumption by 0.5W to 1W.
  • Better audio: The audio circuit incorporates a dedicated low-noise power supply.
  • Neater form factor: Aligned the USB connectors with the board edge, moved composite video onto the 3.5mm jack, and added four squarely-placed mounting holes.
Raspberry Pi Model B+

For more details, diagrams, and videos, please visit Introducing Raspberry Pi Model B+. Because of the new configuration layout many accessories for the B board will not work with the B+ board.

Now, RTL-SDRs: RTL-SDR is a term used describe a very cheap software defined radio. Other names for this device are: RTL2832U, DVB-T SDR, or “$20 Software Defined Radio.” RTL refers to Realtek Semiconductor Corp most widely known for their computer IC network controllers, card readers, and very popular High Definition Audio codec used in many laptop and desktop computers.

SDR refers to “software defined radio.” Typically radio components like mixers, filters, amplifiers, modulators/demodulators, and detectors are implemented in hardware level components. In SDRs these components are implemented by way of software running on a PC or embedded system. The most widely known SDR in ham radio is FlexRadio.

RTL-SDR Dongle

The RTL-SDR is a DVB-T TV tuner dongle based on the RTL2832U chipset. DVB-T stands for Digital Video Broadcasting – Terrestrial used in the eastern hemisphere (Europe, Asia, Africa, and Australia) as their over-the-air broadcast standard. In contrast, North America uses ATSC (Advanced Television Systems Committee) standard for digital television transmission over-the-air, cable, and satellite networks (sources: DVB-T and ATSC).

Antti Palosaari, Eric Fry, and Osmocom were hackers playing around with these receivers and found the signal data could be accessed directly. This allowed a cheap DVB-T TV tuner to be converted into a wideband software defined radio via a new software driver and used as a computer based radio scanner. Add in software packages to expand the capability and you have a system that would cost hundreds or even thousands of dollars.

RTL-SDR Internal Hardware

The current popular dongle is the NooElec NESDR Mini SDR & DVB-T USB Stick (R820T). It comes with an antenna that only works well for very strong signals. Yes, it does come with a Remote but you don’t need it for SDR. They guarantee the NESDR will have an electrostatic discharge diode (ESD) in their dongles. This is useful when handling the dongle or traveling where the possibility of frying it is greater. However, as I found out, if you drop one of them upon returning from Dayton you’re better off getting another because it just won’t work the same!

Let’s dive into some specifics:

  • RTL2832U Chipset close-up

    Frequency range: depends on the device and chipsets used. The NooElec NESDR has a receive range of 24 – 1766 MHz. The previous Elonics E4000 hotness covered 52 – 2200 MHz. However, that company went out of business making the dongle rare and more expensive.

  • Sample rate: maximum theoretical sample rate is 3.2 MS/s (mega samples per second). The optimal sample rate (without any dropped samples) is 2.4 MS/s.
  • Analog-to-digital conversion resolution: 8 bits.
  • Input impedance: 75 Ohms. The mismatch loss when using 50 Ohm cabling is minimal.
  • Connector type: most use an MCX connector. The E4000 uses a
    MCX Connector

    PAL connector.

These $20 dongles only receive. Other dongles offer better performance but come at a higher price. The FunCube Dongle is an example of this. HackRF (10 – 6000 MHz) and BladeRF (300 – 3800 MHz) are SDR radios that will transmit over their given frequency range. That’s right, wideband transmit! These are even more expensive at $300 – $650 (sources: About RTL-SDR and Buy RTL-SDR Dongles).

What about HF? The dongles themselves don’t cover HF. There are two options for reception: use an upconverter to receive the frequency and convert it up to a frequency the RTL-SDR dongle can receive. Make a hardware modification to allow “direct sampling mode.” HF upconverters are anywhere from $50 – $100 (cheaper if you build your own) and offer better performance over the hardware mod. KF7LZE has a round-up of HF upconverters.

This quickstart guide shows how easy it is to setup and start receiving signals. Windows users will probably start out with SDRsharp (also written SDR#) to receive signals. Linux users have a couple options; GNURadio being the best though it is unwieldy because you build out the SDR from scratch.

These make it easy to receive FM broadcast (WFM), NOAA weather radio, amateur radio, or public service frequencies that are still analog. I will show uses and applications of these SDR receivers including a reason you might want to get two (or more) dongles. Hint: it’s not to replace one after Dayton!

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.

Dongle Bits: Raspberry Pi and Arduino

I’m writing a series for The Lake Erie Amateur Radio Association newsletter The Spirit of ’76 and ’88 about microcomputers.  Here is the first article that appeared in the February 2014 edition.  The series also  appears in The Wood County Amateur Radio Club newsletter CQ Chatter April 2014 edition. The series is titled “Dongle Bits.”

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


Raspi_Colour_RI first heard about the Raspberry Pi about a year and a half ago on a podcast I watch called Hak5 in episode 1117. The founder created these small, cheap computers to promote computer science skills in schools. I liked the idea because students would be using technology standards like the ARM processor, HDMI, and Linux. ARM processors are used in many embedded systems because of its system-on-a-chip architecture. It may include the CPU, video, audio, memory, and input/output interfaces on a single chip. ARM processors are used in just about every smartphone and tablet.

Two current popular micro boards are the Arduino Uno and Raspberry Pi. Galileo is a recent Arduino clone from Intel using their architecture. Devices like these are innovations coming out of a prolific DIY, maker/hacker, and education communities. Just to point out, “hacker” in the sense that hams were considered the first hackers: modifiers and builders. Not the people that steal your credit card data.

This overview will focus on the Raspberry Pi. I see more projects using it and I chose it because of my familiarity with Linux. The Raspberry Pi Foundation describes the device as “…a credit-card sized computer that plugs into your TV and a keyboard. It is a capable little computer which can be used in electronics projects, and for many of the things that your desktop PC does, like spreadsheets, word-processing and games. It also plays high-definition video. We want to see it being used by kids all over the world to learn programming.
(http://www.raspberrypi.org/faqs#introWhatIs).

7513051848_9a6ef2feb8_o

The “Pi” comes in 2 versions, revision A & B. Rev. A sold for about $25 and had fewer components. Rev. B is about $35 and comes fully assembled. For simplicity, I will talk about rev. B as it is the current standard. It’s a great choice for all kinds of projects due to the price point. If you’re doing a project and blow up your Pi, it’s not going to break the bank replacing it compared a desktop. The specs are:

RaspiModelB
Raspberry Pi Model B Components

• Weight of 1.6oz.
• 512 MB shared RAM.
• Video input connector for the optional Raspberry Pi camera.
• Video output over RCA or HDMI.
• Audio out over HDMI or 3.5mm headphone jack.
• SD card storage.
• 2 USB ports.
• 1 microUSB for power.
• 10/100 Ethernet.
• GPIO header (General purpose in/out).
(http://en.wikipedia.org/wiki/Raspberry_Pi)

On the software side, the Raspberry PI can run various distributions of Linux. A distribution is the kernel operating system distributed with different tools and programs. Weezy Raspbian is the standard distribution. Project authors may further customize a distribution or make one of their own. As an example, the Occidentalis distribution has modules for Pulse Width Modulation (PWM) and servos already loaded.

Arduino Uno R3
Arduino Uno R3

Though the Arduino and Raspberry Pi are similar devices, they are very different. The Arduino boots its firmware which allows access to all features over the USB port. An application can be loaded or have it run an instruction set when it boots. It is very simplistic in that it can read sensor data, process data, and produce output. All of this functionality must be programmed into this micro-controller.

The Raspberry Pi can run a full operating system with internet browsing, word processing, games; making it a micro-computer. The Pi does not have a Real Time Clock (RTC). The time is expected to be set via the Internet. Development and hacking of the Pi is typically software based, but it can do functions via the GPIO pins. It is a better choice for embedded systems and projects that require interactivity or greater processing power. A new project or other operating system can be loaded by changing SD cards.
(http://codeduino.com/information-and-news/hardware/arduino-vs-raspberry-pi/
http://www.makeuseof.com/tag/arduino-vs-raspberry-pi-which-is-the-mini-computer-for-you/)

A common issue with the Pi is that it can be “touchy.” Problems are usually related to peripheral incompatibilities and lack of current. The Pi should have at least a 1A power supply. If more than two USB ports are needed, use a powered USB hub. When purchasing the Pi and associated hardware, my strong recommendation is to check reviews, the verified components list, or use AdaFruit. Everything on that page will work with the Pi. There are great DIY projects and tutorials on AdaFruit.

I have been telling people Google (or Bing, you know, whichever) “Raspberry Pi [your hobby]” or poke around project sites for ideas. You’re bound to find something interesting!

The coming articles in this series will touch on some Raspberry Pi projects and cover other computer related projects.