How do I get my DMR recordings?

 

Kraken is coming and we all need to prepare for its arrival.  On Tuesday October 19th 2021, Steve K2GOG was invited to the North Star Digital Net to give a quick chat about what does it do and why its important for the future within the broader topic of "software defined radio".

A few people who could not attend the live discussion had asked Jim WA2UMP and Steve K2GOG to see if they could record the audio presentation.   This is a fun problem that needed to be solved first to start this article, so read onward!

How do you record DMR audio?

Steve K2GOG planned to use his Alinco DJ-MD5XTG to talk via his hotspot which reaches the Brandmeister 31630 (STEM) talk group.  A nice feature with this radio, as well as the popular Anytone AT-878 series of radio, is that it can record transmit and receive audio with timestamps and by who was speaking.

Its easy to scroll through recorded audio files one by one or play all your recordings on a loop to play them all in order. This could be helpful if you thought you may have missed some important scheduled discussion or activity on your favorite talk group.

One annoyance is that the recordings save to internal memory on the radio instead of a micro SD card, like on radios such as the D-Star focused Kenwood TH-D74 or the Fusion based Yaesu FT-5DR. 

Both of those radios and even the Icom IC-705, all require the user to remove the SD card from the radio to access recorded audio but that makes it really easy to access those files  on your computer and send them to someone to share interesting transmissions like during a satellite contact. 

In the case with the Alinco and Anytone, you need to connect up a cable to your computer to access the recordings but you can not pull those files off which is super annoying. The manufacturers software seems to lock this function out but would otherwise clearly support this as pictured below.

If you click any of the files listed in photo above, the recording simply plays through the radio speaker but we are no closer to sharing the recordings.

The Alinco DJ-MD5 series of radio uses a simple USB micro cable to program the radio but does not output audio.  The way to solve this problem is to use the headphone port on the Alinco which uses the standard 3.5mm plug found on most all consumer headphones.

Using a 3.5mm stereo to stereo cable, the other end plugs right into the microphone jack on your computer sound card.  If you have a modern laptop which uses a TRRS (Tip, Ring1, Ring2, Sleeve) style connector, you may instead need to use a USB sound card as mentioned in Steve's explanation video below.

Now that we have that problem solved, you can use a program like Audacity with the sound activated record function enabled to "re-record" the audio from the radio to your computer.  While this takes a little while to do, it lets you easily stitch together the audio segments you want with no gaps. 

If you are over a certain age where you may remember double cassette recorders, this activity may bring back memories of less technological days when you had to get creative to make a mix tape from "borrowed" cassettes or maybe songs off the local broadcast station.

Hopefully this modern solution may give you some ideas on getting more from your DMR radio.

Getting back to Kraken

After all that, now we can finally get to the recording you might have missed! 

Here is an MP3 recording mostly of the segment from Steve K2GOG.  

It sounds like he missed a few parts but is otherwise complete. It looks like a time intensive operation to click on all recordings in order, so bear that in mind if you wish to do something like this yourself.

The recorder function works on any "over the air" DMR signal, so using it also to record simplex activity like what took place during the NEARFEST on US national DMR simplex of  446.075 MHz on time slot 1, color code 1 and talk group 99 is another idea.   

But, if you plan to record audio from Brandmeister you can also just use the "Hoseline" function and route that audio from a talk group into Audacity just as easily using virtual audio cables. 

And with that, I hope you are looking forward as much as Steve is to getting the new Kraken once its starts shipping in March 2022.

Pro Tip: Finding DMR Activity

As more and more users of digital voice amateur radio shift towards hot spot devices instead of local repeaters, it gets hard to find where people in your area are using DMR.

Since hotspots have such limited range, you would not likely be able to hear them "over the air" and there is not really any way to simply "scan the band" looking for activity like one may do on 2m or 80m.  So, how do you find DMR activity?

DMR: Get Predictive

Is this suggestion cheating? Not really.  There is a way you can use one of the many somewhat hidden analytic tools to find out what talk groups are most active and when.  This will help you learn when and where to spend time "lurking" since there are 1,439 officially set aside talk groups according to this nice Pi-Star DMR BrandMeister Talk Group page.

Using talk group 31630 (STEM) as an example, the chart below is predictive in the sense that every Tuesday evening at 20:00 hours Eastern US time, is a big spike of activity for a little over an hour. This is when the Northstar Digital Net takes place.

Another example on when you may find activity if you are traveling in the state of Louisiana is shown below by looking at talk group 3122.

How about if you want to feel really special and have "Nationwide US" all to your self with fewer people constantly asking for a radio check or signal report?   06:00 AM Eastern US may just be the time for you to sit on talk group 3100.

Where do you get these charts?

Here is where to go and find some possibly interesting talk groups and times to see what sort of activity is taking place.  https://brandmeister.network/?page=callstats

And now you know how to find the best of the best on DMR. 

How To Guide: Satellite Based APRS iGate

There is so much amazing activity these days surrounding satellite and software defined radio (SDR), but there are not many clear and current guides for those interested in creating receive only gateways to send satellite born APRS signals over the internet. Let's change that.

APRS & Satellites (and balloons, drones, etc)

Currently there are three active satellite based digipeaters in low earth orbit. The International Space Station (ISS), PCsat NO-44, and SAT NO-84 all operate on 145.825 MHz.

There is also a fourth APRS satellite named FalconSat-3 that was turned over from the United States Air Force in 2017 for amateur radio use, but is operated on 145.840 MHz and requires a little more work to use. There are other amateur digital mode satellites in the planning stages.

Image Courtesy of  http://aprs.org/outnet.html

What is an iGateway?

An iGateway is nothing more than a radio receiver that is connected to the internet. Signals received by the antenna are passed from the radio over the internet.  The iGateway is designed for digital or data signals and not voice however. Websites such as findu.com and aprs.fi are two examples are where the benefit of igateways can be shown and show APRS data.

There is also the Othernet (Formerly known as Outernet) project that sends information from its ground station back up towards different satellites that "datacast" to special receivers such as the Dreamcatcher. Properly addressed APRS messages are in turn broadcast over this separate satellite network. This is not the same as an iGateway, but does add some other unique potential.  For an amateur to route a message with APRS through one of the mentioned satellites earlier, one must use the path of "OUTNET" instead of "ARISS".

General users of APRS for ground based modes typically leave the path as WIDE1-1 or WIDE2-1, but those interested in satellite communications must use the alternatives listed since a satellite works differently from a propagation perspective to ground based or even low altitude aircraft or balloons.

How To:  SDR & Raspberry Pi iGateway

To create an iGateway you will require:

• An inexpensive USB SDR

• Raspberry Pi Computer or other similar device

• Antenna capable of overhead reception

• Various cables and stuff for your installation

There are way too many variables on antennas and cabling specific to every installation so we will keep this brief and skip that part. The shortest run of coaxial cable from antenna to radio is needed. The highest and clearest view towards the horizon in as many directions as possible is required for optimal reception when considering setting up a iGateway.

The satellites we will be monitoring pass over most locations about 3-5 times every day for just a few moments, so it's possible a APRS capable satellite will pass over once every 60-90 minutes.

Lets setup the software bits and bobs....

The main goal of this article is to only share the steps for configuring software to get a SDR dongle working with a Raspberry Pi.  These steps can also work for those looking for alternate uses for SDR based hardware such as the now out of date L-band focused Dreamcatcher v 2.03 boards that were replaced with the newer Ku-band Dreamcatcher v3 and likely could be used too.

The real magic here is the software and how it will all work together.

First step, is get a working operating system on your device of choice such as the Raspberry Pi or Dreamcatcher v2.03. Most of these instructions will work for other linux based computers but is not the focus of this article.

Please run sudo apt-get update and sudo apt-get upgrade first to ensure your operating system is current and has most all of the popular packages installed for general use before continuing.

Second step, involves setup of Dire Wolf which translates sound to packet decoding. Run the following on your device to install it.

sudo apt-get install libasound2-dev
git clone https://github.com/wb2osz/direwolf
cd direwolf
make
sudo make install
make install-conf

Next, you need to configure the operating system to take virtual audio from an inexpensive SDR dongle and pass it to direwolf.  Go ahead and plug in your SDR dongle to your raspberry pi. If you are using a Dreamcatcher, there is no need since the SDR is part of the board already!

sudo apt-get install cmake build-essential libusb-1.0-0-dev
cd
git clone git://git.osmocom.org/rtl-sdr-git
cd rtl-sdr
mkdir build
cd build
cmake ../ -DINSTALL-UDEV_RULES=ON -DDETACH+KERNAL_DRIVER=ON
make
sudo make install
sudo ldconfig
sudo reboot

Let's pause for a moment and test the SDR to make sure its recognized.

run "rtl_test"  and ensure you get a status update like this before continuing. This shows that the SDR is being recognized by your Raspberry Pi, Dreamcatcher 2.03 or other single board linux computer.

Now we need to configure Dire Wolf and the best way to do that is copy some of the great work that Keith G6NHU has compiled. Head on over to his interesting site here:

http://qso365.co.uk/2017/02/a-guide-to-setting-up-an-aprs-receive-only-igate-using-a-raspberry-pi-and-an-rtl-sdr-dongle/ 

The only basic change you need to make is to select the correct frequency. In the United States much of the APRS activity is on 144.390 MHz, but since we are interested in satellite based APRS, change it to 145.825 MHz instead.

What did you say about balloons?

Perhaps you may tire of the same general activity on APRS terrestrial activity or even what may be bouncing off a satellite.  The next logical thing to look into would be tracking a balloon of some sort.

Taner DB1NTO has a new product out to cater to people looking to track something that can only carry a very light weight device.  He calls it PicoAPRS Lite and should open up lots of possibilities to experiment with alongside perhaps with a portable version of an iGateway connected via cellular hotspot.

If anyone in the Hudson Valley is interested in experimenting with tracking objects other than a house which does not move much, or a car, lets start talking.

The STEM (31630) DMR talk group seems a logical spot as well as the AMSAT (98006) talk group, so lets make something happen here when spring time arrives!

• More about STEM 

• More about AMSAT

Visit the HVDN Activity Calendar to learn of upcoming discussion, projects, meetings and events 

Happy Monday!: ISS & STEM Academy Make Contact

On July 2nd 2018 at just past 11:30 AM was a scheduled contact between the International Space Station and the Pearl technology STEM Academy in Peoria, Illinois. Students submitted questions in advance that astronaut Serena Aunon was going to answer by using the space stations amateur radio equipment.

“Nothing beats waking up on a technological marvel and then starting the day off with an antique method of navigating. Sextant Operations from @Space_Station! Still considered a potential backup method of navigation for future vehicles…” said NASA astronaut Serena M. Auñón-Chancellor on her Twitter

Since New York where HVDN is located was in the general foot print of the space station orbiting overhead at 200+ miles high on its way over Peoria, here is a brief recording of some of the questions asked before the space station got out of range.

Recording:  NA1SS operated by Serena Aunon answering questions facilitated by W9DWJ

The reason only one side of the conversation was heard was because the ground station in Illinois is too far to hear directly on VHF spectrum in New York directly.  

The ground station setup at the STEM academy was transmitting on an up-link frequency to the ISS of 144.49 MHz and the ISS was transmitting back down on the 145.80 MHz down link. 

Start and end positions on where the ISS was first heard and when it was out of range.

It is fantastic for students to be able to leverage technology to have real time contact with the space station and to instill an interest in science, technology, engineering and mathematics at an early age.  Serena is a great role model for younger generations to see what they can be when they grow up.

Amateur radio allows anyone to experiment with this hobby, be they young, old, male, female, technical, non-technical, English speaking or otherwise.  There is much that can be learned with each other and HVDN plays an active part in the Hudson Valley area of New York in fostering interest in emerging and exciting parts of amateur radio.

Here is the radio used to record the ISS contact.

HVDN has recently launched the STEM Talk Group available on the Brandmeister DMR network which uses DMR technology to create easy and clear communications globally. 

More information can be found at the below link and perhaps this great resource can be used to connect explorers, astronauts, engineers, or anyone else who can share unique insight about amateur radio, what its capable of and how it can influence future generations to better communicate. 

• More about STEM Talk Group 31630

• More about Astronaut Serena Aunon

ANNOUNCEMENT: On Saturday July 6th, Steve K2GOG will be taking a ride in a hot air balloon as part of the Balloon Festival at the Dutchess County Fairgrounds in New York. Anyone interested in arranging contact via TG 31630 with him, can listen on TG 31630 between 6:00 AM and 8:00 AM New York time. He will be routed on to the network via the N2MCI repeater located in Kingston, NY.  Steve's location will also be found on the aprs.fi website under the N2HVD-11 call sign. He will also be making direct contact on suggested analog or digital frequencies too on 2m, 1.25m, and 70cm below

• 146.52 MHz Analog FM
• 223.500 MHz Analog FM
• 446.00 MHz Analog FM
• 446.075 MHz Digital DMR (TG 99, CC1, TS1)
• 145.790 MHz Digital DMR (TG 99, CC1, TS1)

Watch! Two Time Slots & SDRangel In Action

DMR is confusing for some people. SDR is even more confusing for others.  What happens when you combine the two?  Mass hysteria?  Global epidemics? Accelerated excitement?

Due to a delay in circuit board re-design for the the Modern Field Strength Meter project, we bring you something different for this week (and possibly next)

This article builds on past written content and accompanying videos to show some of whats possible today when combining the two.

Some Brief Background First

DMR has seen a lot of growth because it is cheap to get started and talk around the world.  SDR adoption for many started with inexpensive USB dongle type of receivers before moving to something more capable. Many SDR dongle purchasers hoped to hear signals from around the world using these cheap receivers.

For a sum total to a new ham who may invest less than $300 in the amateur radio hobby, they can purchase a dual band DMR/FM hand held radio, multi-mode digital hotspot, USB SDR dongle and a few accessories such as antennas, power packs, etc. All this gear permits both local, global and emerging aspects of the hobby to collide and find people with like interests to talk with others about.

For comparison, when I got started in the hobby in the mid 1990's, the starting point for many was a VHF only Radioshack HTX-202 handheld radio for about the same $300! This permitted only local communication and while it still works today, there is a world beyond 2m.

“You realize that our mistrust of the future makes it hard to give up the past.”
Radio Shack is out of business by the way...

With DMR being the most popular digital voice mode that permits  local and global communication and an SDR being able to receive voice and non-voice communications locally and globally, there is a lot of capability at hand today for a new ham. Compared to local VHF activity, DMR provides the ability to talk with not the same local people all the time, but with the voice quality of local repeaters.

Many new hams experience getting on the air for the first time on the VHF 2m band and some quickly tire by talking to the same few people generally about the same thing. If there are not enough common interests with those locally, that new ham often decides the hobby is not for them.

Even so, many new hams who tire of 2m and move on to HF for long range discussion, get frustrated by higher expense, more planning for antennas and potential lack of people with common interests to talk to depending on when HF bands are stable or not.

The Best DMR Feature

DMR uses similar technology to second (2G) and third generation (3G) cellular communications known as TDMA.  The unique thing about TDMA based DMR is its ability to have two discussions on the same frequency at the same time with zero interference.  More about that here on HVDN.

Many have heard this, but not seen it in action.  Here is a brief video:

The laptop in the foreground is running SDRangel software that is receiving signal from a dual time-slot hotspot on a SDR nano3 USB dongle. The frequency for this test on my dual time slot hotspot is 432.565 MHz.

The SDR Nano v3 retails for less than $30 and is very small.
A standard SD card is shown at left for size comparison.

On the laptop in the video background is showing the call-sign, time slot and talk group (virtual frequency) as its received by the hot spot.

The audio is being output by the foreground laptop and you will see how it coincides with the information on the background laptop.

This test was conducted at a time when a lot of activity is present on popular DMR talk groups known as TAC310 and Worldwide 91.

The same SDR dongle can be used to receive signals from local amateur radio repeaters that are DMR, analog FM or even some less popular modes such as Yaesu Fusion, Icom D-Star and commercial focused NXDN and P25.

As evidence by the video,  both local US and international amateur radio operators are able to talk to one another without having to invest in large antennas or high powered radios such as those used on HF for voice communication.

What is fascinating about DMR is how many of the older ham radio operators have taken to DMR for casual discussion instead of just using HF.

You never know who you will hear on amateur radio and where they are from. Investing in modern technology will allow a new or experienced ham to try new things for little expense before deciding where else to invest in.  This "modern ham" starter package may cause reason for purchase for things such as:

• An HF radio
• Outside HF, VHF or UHF antennas
• A better computer 
• A higher end SDR
• Getting better educated about SDR and DMR
• More education on computer/ham convergence

If there is interest in anything mentioned in this article, look for many of the HVDN members on DMR TG 31368 which is geographically focused for those residing in the mid Hudson Valley of New York. 

You can also look for discussion of combined topics on the new STEM talk group 313630.  More detail about that and its focus here stem.hvdn.org