AO-92 & 3 steps for communication success

In January of 2018, the AO-92 satellite was put in orbit and was soon operational for amateur radio operators looking to communicate with other like minded enthusiasts.

A recent contact made between Steve K2GOG in FN30 and Alan VY2XU in FN86 using AO-92 satellite on April 26th morning to show a typical satellite communication footprint.

The AO-92 satellite, also known as Fox 1D was launched from the Satish Dhawan Space Centre in Sriharikota, India.  This small "cubesat" allows users on Earth to transmit on 435.350 MHz and then get real time repeated back out from the satellite over 145.880 MHz for others to hear.

The orbit height is about 250-320 miles above Earth at any time, so any station within a radius covered below the satellite is possible for just a few minutes until the next time the satellite passes over again. The potential range of communications is almost 800 miles!

30 other "cubesats" were deployed at the same time from the PSLV-C40 rocket

It is very easy to hear the AO-92 using a basic directional or whip type of antenna and appropriate radio. The receive or "down-link" frequency of 145.880 MHz is not as affected by the speed at which the satellite is traveling which is about 5 mile per second.

However, the transmit or "up-link" frequency is and the user needs to slightly adjust above or below 435.350 MHz depending if the satellite is headed towards or away the user location. This is known as "Doppler Shift".

The AO-92 satellite will appear to be on frequency when it is as close to the user as possible, but as it moves further away it will seem up to 15 kHz different which makes communicating through a satellite like this a little challenging at time.

The higher up in frequency has a greater affect when it comes to the Doppler affect which is why the satellite uses a lower 145.880 MHz in order to make it easier hear and encourage people to listen for it.

Beyond knowing the correct transmit and receive frequencies, the user also needs to transmit a sub audible tone of 67 Hz.  This is needed to prevent interference from getting into the satellite.  This tone is almost like a secret password needed to use the satellite. Without it, you can hear the satellite fine, just not be able transmit and be repeated back to Earth.

Helpful tips for using the AO-92 satellite

• Listen a few times to get familiar what satellite users talk about before transmitting
• Program your radio in advance of the satellite pass
• Be courteous to other users and keep communications short

Using less than 2 watts of transmit power is all that was needed to contact Alan 600 miles away thanks to the AO-92 satellite.   To generate a helpful grid overlay to easily identify where other stations are located using as few as 4 characters, here is a nice file provided by Ari  OH2ECG to be used with Google Earth.

Presentation: Satellite Spectrum & Amateur Radio

Steve K2GOG presented on "Satellite Spectrum & Amateur Radio" at the Trenton Computer Festival on March 23rd alongside another 50+ technology and innovation focused topics.

The goal of the presentation was to cover the valuable radio spectrum available through amateur radio and promote its use through innovative communication applications on earth and in space thanks to underlying computer technology

How much spectrum do we have?

For those that are already licensed amateur radio operators, you may have a printed version of the below spectrum chart that the ARRL publishes or at least have seen it somewhere before.

In the United States and most other countries, there are different license classes of amateur radio operators. Some countries restrict the transmit power or operating modes as well as what frequencies can be used depending on your license restrictions.

Steve decided to add up all the spectrum that is accessible to the three current United States amateur radio licenses and further highlight just how much of the total 23,126.7731 MHz of discontinuous spectrum can be used for satellite related communications. The results are pretty interesting.

What really separates the Extra from General or Technician?

Sometimes it is good to be simple. Get the highest license possible and ensure you never have to worry about operating on the wrong frequency. Currently, the only thing that separates the highest from the lowest license class in terms of spectrum access is 3.9321 MHz of operating capability.

The difference in spectrum for the different license classes is mostly found in the HF bands ranging from as low as 135.7 kHz and up to 29.7 MHz. The only other spectrum not accessible to the technician class license is the 219 to 220 MHz portion of the under utilized 1.25m which many consider as being only from 222 to 225 MHz.

The remaining spectrum is all available to the Technician class license holder!

What if your not interested in long range "HF" communication?

With advances in radio receiver sensitivity and advanced low signal to noise ratio transmission modes, large antennas often associated with HF operation are not always needed.

However, even with specialized magnetic loop antennas and FT-8 digital text modes -nothing beats a full sized dipole for global communications on the 14 MHz or 7 MHz bands often referred to as 20m and 40m respectively and not everyone has the space or interest in such an antenna.

Radio propagation theory does not always guarantee communications are possible at all times of the day which may frustrate some people who only have limited times to "play radio" with HF spectrum.

RF HF propagation is just like the weather

A forecast is still just a forecast and is generally correct, but the difference between satellite communications and HF is the predictability.  For those with limited time to gain "radio communications" gratification, satellite communications may be worth a look.

You can easily calculate when a satellite will pass over head in the case of the "Low Earth Orbit" satellites covered in Steve's presentation for example. It certainly would be great if the weather was like that, wouldn't it?

Depending on satellites

One shortcoming of most satellite communications is that you are reliant upon a man made piece of technology flying over your location in order to make long range contact.

The other shortcoming is you can only make contact with other stations in the footprint of the satellite, which is different than HF since technically you can talk around the world and sometimes even hear your own echo under the right conditions.

Benefits of satellite communication is that you can get a lot of "ham radio" done in a very short amount of time given the brevity of low earth orbit satellites for those not fortunate to live in the foot print of the only current geosynchronous satellite that covers all of Europe, Middle East, Africa, India and a few other countries across Asia.

Fight:  Innovation in amateur radio

The first amateur satellite put into orbit was OSCAR-1 in 1961, just 4 years after Sputnik was put into orbit as the first ever satellite. 

Now almost 60 years later, there has been a total of over 100 satellites put into orbit and most of them being fully operational, with a few example success stories being AO-7, SO-50, AO-92 and QO-100.

In total and thanks to international regulatory efforts, all this satellite success requires spectrum to be set aside since managing who or what can use certain frequencies is more challenging compared to how a specific country can manage its finite spectrum resources.

Its pretty clear that there has been a lot of innovation within the amateur radio satellite spectrum, but much of it has yet to be fully realized.

One example of how technology originally meant for meteor scatter or earth-moon-earth communications which involves bouncing signals off of these non-man made satellites is known as low signal to noise ratio modes, mostly invented by Joe Taylor, K1JT.  The modes can now be found in use on the HF bands rather than for space related contacts. Here is how computers and amateur radio together create innovation.

Technology Improvements: We all benefit 

OSCAR 100 which was put into functional orbit by the Qatar Amateur Radio Society along with technical guidance from the German branch of the Amateur Satellite Corporation known as AMSAT pushes the boundaries of technology and spectrum management.

In 2018, various digital voice modes such as those enabled and made more accessible due to Multi Mode Digital Voice Modem (MMDVM) hot spot devices created an issue for certain satellites operating in the congested 435 to 438 MHz band.   A LEO satellite such as AO-92 speeds overhead at an average altitude of 220 miles and can easily be interfered with by 20mW hot spots and the lower power radios people use to access them. OSCAR 100 is the only satellite that does not have this issue.

Price has driven the adoption of MMDVM hot spots and radios such as the Anytone D868, TYT MD-380 and others. 

Today, thanks to the QO-100 satellite, there is a lot of rapid innovation taking place which shows that cost and user benefits generate lots of excitement that highlights the growth of the radio arts as specified in FCC Part 97.1.

The only unfortunate thing for North American amateur radio operators is that its not possible to utilize this innovative satellite and its great use of spectrum because it is in geosynchronous orbit. However, the AMSAT project GOLF is coming near which is exciting!

Looking beyond, satellite is just one way to show innovation through the use of spectrum. The future of amateur radio is dependent on finding other innovative applications for spectrum, so why not look at what else may be possible outside of the HF bands, even going as high as the mmW bands -
GigaHertz.... not MegaHertz!!!

Full Presentation & Added Bonus

The complete, but non-animated version of the presentation can be found at the link below in addition to the amateur spectrum database compiled to help develop some of the content Steve K2GOG presented both at the HVDN Quarterly meeting this past March 11th as well as TCF on March 23rd.

HVDN Satellite Spectrum Presentation

HVDN Amateur & Satellite Spectrum Database

Amateur Satellite Basics: Where, When & What to listen for

Interested in trying something new using your handheld VHF or UHF radio?  How about putting that old scanner to use or using one of those other bands not used in your "all mode/all band" HF radio?  What about using that $20 software defined radio dongle you may have gotten for Christmas?

Diana Eng photo with home made antenna in a 2009 Make magazine article.  Look here for more info

Consider satellite listening as your next adventure!

This article will only focus on when, where and what to listen for. Later articles will cover transmitting and other related best practices in using the amateur radio satellite constellation for your enjoyment.

What is out there to listen to?

The below chart from the radio amateur satellite corporation or AMSAT for short shows the name of current satellites and general usage patterns. As you can see, there is a lot floating and spinning around Earth that are amateur focused satellites.

Where to listen for these satellites?

There are sub-bands set aside for satellites and to ensure there is minimal interference from other users in different parts of the world or for those with other interests not related to satellite operations.

In the United States, the ARRL and FCC have negotiated a general band plan along with the ITU and other regulatory bodies such as OFCOM, JARL and many others. Here is a summary taken from the ARRL website for where these special allocations of frequencies exist for satellite only activity.

• 10m band  satellite down-link from 29.3 to 29.510 MHz
• 2m band new OSCAR sub band from 144.3 to 144.5 MHz
• 2m band linear translator inputs from 144.5 to 144.6 MHz
• 2m band linear translator outputs from 145.1 to 145.2 MHz
• 2m band OSCAR sub band from 145.8 to 146.0 MHz
• 70cm International satellite sub band from 435.0 to 438.0 MHz
• 23cm band satellite up-link sub band from 1260 to 1270 MHz
• 13cm band satellite sub band from 2400 to 2410 MHz

The above adds up to almost 24 MHz of total band width available for two way satellite communications.  Not included above are other frequencies available for "Earth-Moon-Earth" communications where you can bounce your signal off the moon as a passive repeater to communicate to other stations elsewhere on Earth. Also not included are frequencies at the 3.3 GHz, 5.6 GHz and 10 GHz frequency bands also used for satellite communication.

Have a look for more detail here on the ARRL website: http://www.arrl.org/band-plan 

Making it more simple

The below frequencies would be a good starting point for just listening, so save them into a radio that you have plenty of left over empty channels in or some other radio you do not use too often.

FM based satellites (down link frequencies)

• SO-50 on 436.795 MHz
• AO-85 on 145.980 MHz
• AO-91 on 145.960 MHz
• AO-92 on 145.880 MHz
• ISS on 145.800 MHz ( Over North America only)

There are a few others that can be looked up on the AMSAT website and the above are the most easy to listen for currently.  https://www.amsat.org/fm-satellite-frequency-summary/ 

SSB based satellites (down link frequencies)

• FO-29 on 435.8 to 435.9 MHz 
• AO-73 on 145.950 to 145.970 MHz

These will be in side band mode and may either be USB or LSB depending on what is sent up via up link and is then inverted on the way down. Other SSB or "transponder" satellites can be found here: https://www.amsat.org/two-way-satellites/

Data focused satellites (down link frequencies)

• APRS via the ISS on 145.825 MHz
• APRS via NO-44/PCsat on 145.825 MHz

There is a lot more not even touched on in this article such as FalconSat, LilacSat, XW-2 Series and others, but all the above should be easy to hear with even modest antennas such as a 3 element tape measure beam or a simple gain "rubber duck"

How to find when to listen?

There are many applications such as Orbitron, Gpredict and others for PC or MAC based computers, but are not very portable.  For an Android based smart phone, look for "ISS Detector" in the Google Play store. It does much more than just predict when the space station is overhead.

AMSAT has a prediction tool on its website here:  http://www.amsat.org/track/index.php

Also, NY2O has a great website as well for finding when to listen: http://www.n2yo.com/passes/amateur-radio.php 

Next steps?

K6KLS has a great website for getting started called http://www.work-sat.com and is worth having a look for more info.

There are also a number of dedicated discussions taking place on Echolink, D-Star and DMR where satellite enthusiasts gather to talk about best practices, so have a look at the HVDN activity calendar to learn more. 

Use it or lose it: Death of 3.4GHz

Wireless spectrum is what makes amateur radio valuable. Without the ability to experiment at different frequencies, "ham" radio will stagnate into being known only for what was up until today 0.0163% of its total available spectrum. This is totally NOT fair! 

What else beyond HF?

The high frequency HF or "shortwave" bands which are used for long range communications is what much of the public know amateur radio for. In times of emergencies or most any regular day or night, very low speed data or narrow band voice communications can be heard across a variety of sub-bands that are only to be used for amateur radio mostly between 1.8 MHz and 30 MHz.  Moving higher up the spectrum chart, much higher speed data and digital voice communication has been gaining in popularity globally.

As noted in a past presentation on satellite communications given at the Trenton Computer Festival when humans were able to gather in social settings with no fear of global pandemic,  Steve K2GOG shared an overview of how much discontinuous spectrum is available to all three classes of amateur radio operators in the United States.

Amateur radio satellite communications

While ham radio is known for its long history surrounding the so called "short waves", once you get beyond 30 MHz, the actual wavelengths get much, much, much shorter and commercial users have long used spectrum just above or below where amateur radio operations live in the VHF, UHF and SHF spectrum. Within these higher bands, there are specific portions set aside for satellite communications.

While there are some tiny portions of amateur radio spectrum that are dedicated for only satellite communications, they add up to over 300 MHz in what could be considered the more easily accessed spectrum between 7 MHz and 47 GHz.

While there is no commercial users likely looking to take back spectrum under 30 MHz, there are a few HF satellite frequencies in use, with examples being the very old AO-7 satellite and a few new Chinese satellites that will start using the 21 MHz band. 

Most amateur radio operators have been exposed to educational school contacts or narrow band picture sharing known as "slow scan television" by way of the International Space Station which mostly uses the 145 MHz spectrum.   

More specific satellites that act as "bent pipes" or repeaters often use 435 MHz as an uplink frequency and 145 MHz for a downlink.  To date, there is limited use of other frequencies above the 435-438 MHz satellite band, with satellites such as AO-91, AO-92, SO-50, FO-29 and RS-44 as a few of the more popular satellite destinations for amateur radio experimenters today that use these frequencies.

The AO-92 satellite also uses a 1.2 GHz uplink during specific times to help show use by the amateur radio community in an otherwise less frequented portion of spectrum, which much like the 3.4 GHz band, has been under attack from commercial users who could benefit from valuable amateur radio spectrum.  

The QO-100 satellite relies upon a 10 GHz downlink and 2.4 GHz uplink and this makes it the most advanced satellite that is accessible to amateur radio operators today, but just not in the United States due to its stationary position covering all of Europe, Asia, Africa and parts of South America.

The neighbors have better stuff

Over the past two years, European regulators such as CEPT and OFCOM tried to to make a case to take away parts of the 145 MHz, 1.2 GHz, 2.3 GHz and 3.4 GHz allocations to help expand different commercial services such as long range aircraft positioning and different "Internet of Things" applications along with different applications that can be considered as part of the 5th generation of mobile communication, often shortened to 5G. 

While fending off the recent attacks on the important bottom part of the L-Band from 1240-1300 MHz was successful as well the somewhat distracting 145 MHz allocation battle,  the spectrum just below the common 2.4 GHz Wi-Fi band was lost to commercial users in Europe. 

Within the United States, the Federal Communications Commission has decided to "delete" the ability for amateur radio operators to use its allocation in the 3.4 GHz band due to the needs of 5G, especially that of CBRS which will drastically change the way spectrum is licensed moving forward.

We need to change

There is nothing wrong if HF focused operation is what is of most interest to you or anyone looking to get involved in amateur radio today. Those that decide to just spend a casual weekend enjoying the already well understood and no longer innovative 3.7 MHz, 7 MHz and 14 MHz bands are akin to being a bunch of "home bodies" and those that are easily pleased and that is ok.

While it is possible to take HF equipment out in the field and operate from battery power and make contacts with others using voice, Morse code or digital data modes such as  PSK31, FT4 or JS8CALL, this does not advance the hobby if we are trying to defend our spectrum. This use case demonstrates a level of converged activity.

In the next few decades, the novelty of HF based communication will be much harder to entice a next generation of amateur radio operators to unless they first are shown all the amazing things that can be done across other frequencies and applications such as satellite based communications.

We owe it to the next generation of prospective amateur radio enthusiasts to find differentiated applications for the 144 MHz, 435 MHz, 1200 MHz and all the way up to 60 GHz if we wish to remain relevant  rather than as a forgotten hobby deep rooted in the evolution of electronic innovations we have seen over the last 100 years.

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 

Mr. President: Dialing for satellites?

Ah, the ubiquitous DTMF keypad still has some relevance as a modern communications tool in the age of voice assistants, location technology and digital communications. Lets find out if that is true.....

What is DTMF?


When you press the buttons on a telephone or most radio keypads, a connection is made that generates two tones at the same time. A “Row” tone and a “Column” tone. These two tones identify the key you pressed to any equipment you are controlling. If the keypad is on your phone, the telephone “Central Office” equipment knows what numbers you are dialing by these tones, and will switch your call accordingly.

If you are using a DTMF keypad to remotely control equipment, the tones can identify what unit you want to control, as well as which unique function you want it to perform.

How do you dial satellites with DTMF Mr. President?

Not all amateur radio satellites focus on providing voice, packet, location or image sharing. A few have incorporated APRStt which makes for novel quick communication of both user call sign and location using one nice short string of DTMF codes.

Any one who has watched or conducted amateur satellite activity may be familiar with the grid square or maidenhead location system.   Using only two capital letters, two numbers and two lower case letters can the geographic position with accuracy of 7.5 miles.

While that may not seem too accurate, its good enough for quick general location exchange.  Simply speaking into a radio that you are located in FN31 or FN31bw is far easier than saying 38°53'52.6"N 77°02'11.4"W or even 38.897933, -77.036500.

Using APRStt, you can simply press *13315246402164# which works out to K2GOG located in FN31bw.   The time it takes to send 16 characters is less time than it took to read this last sentence.

For those interested in data satellite communications, but do not own a radio capable of the popular AX.25 based 1200 baud APRS functionality like the Kenwood TH-D72, TH-D74 and the newish Lanch HG-UV98 to be reviewed on HVDN later this summer, this may be an interesting communication method to experiment with.  Courtesy of Bob Wood, WA7MXZ, here is a nice calculator to compute your own APRStt sentence.

Any amateur radio with a DTMF keypad from the lowly $25 BaoFeng radios, to more current mainstream radios like the Yaesu FT-70R and about 300+ other models to the super cool looking military "knock off" variants of the PRC-152 found on E-Bay would work just the same for APRStt since they can all send DTMF.

But how to decode APRStt?

DTMF is hard by ear to determine the DTMF code sent, so the soon to launched PSAT2 includes a  DTMF to voice transponder which will read back via computer generate voice a fully formed APRStt sentence it receives.  There are also many other very interesting things that PSAT2 will also permit such as:

• PSK31 10m band up-link/UHF FM down-link

• SSTV camera with UHF down-link in the same pass-band as PSK31 signals

• DTMF Grid Square up-link and Voice/APRS down-link for Grid position reporting

• DTMF Text messaging (APRStt).

• APRS text messages up and Voice down.

• Conventional APRS digipeater 

Some may choose to experiment with an SDR tuned to the appropriate PSAT2 frequencies and decode APRStt with suitable software or maybe even use an Arduino based simple DTMF decoder since not many amateur radios can decode DTMF easily. 

The radios that can and often include other uses for DTMF multi tone decoders and could be programmed ahead of time to un-mute when a known APRStt is heard, but that sounds frustrating.  Maybe someone will "hack" a TYT MD-380 or other to show DTMF since it is capable at multi tone decode?  Hmmm.....

PSAT2 details please?

Once this interesting cube-sat reaches orbit and is provisioned for operations after the June 23rd or 24 or 24th 2019 launch window, we will be able to track the satellite and hopefully learn if 28.120 MHz is the actual 10m frequency to be used for the PSK31 transponder up-link or not.

PSAT2 is sure to be an exciting satellite and we wish it success and to help continue to make ham radio great again!

Related Reading

• APRS PSAT2 Details Page

• How To Guide: Satellite Based APRS iGateway

• AMSAT Satellite Status Tracker

Field Report: LimeSDR Mini Satellite Ground Station

Crowd Supply is where the Lime SDR and LimeSDR Mini can be purchased that have been reviewed and included in past HVDN articles such as the "Satellites & Amateur Radio Spectrum" presentation given at the Trenton Computer Festival by Steve Bossert, K2GOG earlier this year.

Many other interesting crowd funded projected can be found on Crowd Supply as well.  Be sure to check it out.  Our hope at HVDN is to inspire additional interest in the benefits of creating interest in a geosynchronous satellite to cover North & South America in the future.

This below article was originally posted on the Crowd Supply website thanks to Daniel Estévez.

My project uses a LimeSDR Mini as the basis for a ground-station for the amateur radio transponders on the geostationary satellite “Es’hail 2” (known as “QO-100” by the amateur radio community). This satellite includes two linear (also called “bent-pipe”) transponders, one of which is 250 kHz wide and is intended for narrowband modes, such as single-sideband analogue voice, text-based digital modes, and telegraphy. The other is 8 MHz wide and is intended for DVB-S2 and other wideband digital modulations and experiments. The satellite covers one third of the world’s surface (from Brazil to Thailand) and represents the first ever amateur radio payload in geostationary orbit. It also provides an incredible platform for experimenting with different communication schemes.

The downlink of the satellite is on the 10 GHz band, so an inexpensive satellite TV LNB can be used to receive and down-convert the signal to an intermediate frequency of around 700 MHz, where it can be easily processed by SDR or conventional radio receivers. The uplink to the satellite is on the 2.4 GHz band. Many people are using an upconverter to translate a signal from around 430 MHz to 2.4 GHz. However, using a LimeSDR it’s possible to generate the 2.4 GHz signal directly.

My design is enclosed in a weathertight box, so it can be mounted outdoors next to the transmit antenna. This is important, as it limits losses in the coaxial cable feeding the antenna. Losses at 2.4 GHz can be quite high, so it is desirable to keep coaxial cable runs as short as possible.

Using a narrowband signal through the satellite transponder does not require much power. In fact, many people are using an inexpensive WiFi amplifier module to obtain around two watts of power. However, the DVB-S2 requires much more power, especially if using a symbol rate of a few Msps to transmit high-definition video. Therefore, my weathertight box includes a 100 W amplifier, which is a repurposed amplifier for UMTS on 2.1GHz.

The LimeSDR Mini does not provide enough power to drive this 100 W amplifier. So I used a Mini-Circuits GALI-84 MMIC to boost the output of the LimeSDR from around 0 dBm to 20 dBm, which can comfortably drive the 100 W amplifier. The GALI-84 driver amplifier was built using a kit from MiniKits.

To control the LimeSDR Mini, a Beaglebone Black ARM single-board computer is included in the weathertight box. The Beaglebone Black is connected to my LAN by Ethernet, allowing control of the LimeSDR Mini as well as the other equipment (for instance, enabling or disabling the RF power amplifiers).

A power supply is also included in the box to convert from 230 VAC to 26 VDC for the 100 W amplifier, which needs a lot of current. Currently, a 10 A power supply is used, but this doesn’t provide enough current, so I plan to upgrade to a 30 A power supply. The other equipment is fed from the 26 VDC by using some small DCDC converters. The Beaglebone Black uses 5V, the GALI-84 amplifier and the 100W amplifier bias run at 12V (with an enabler controlled by a GPIO pin of the Beaglebone Black), and the amplifier fan runs at 12V (always enabled). A TMP36 temperature sensor is mounted on the heatsink of the 100W amplifier and controlled by the Beaglebone Black.

Currently, this weathertight box is only used for the uplink. For the downlink, the IF signal from the LNB goes into my home through an inexpensive 75 ohm coaxial cable to a LimeSDR which is connected to my laptop via USB3. I plan to also route the IF signal from the LNB to the LimeSDR Mini inside the weathertight box, so as to allow any computer connected to my LAN by Ethernet to control both the uplink and downlink of the ground-station.

Another planned modification to the setup is feeding a reference signal (for example, 10 MHz) into the weathertight box to be used as a frequency reference for the LimeSDR Mini. For narrowband signals at 2.4 GHz, the frequency stability of the transmitter is quite important, and while the TCXO on the LimeSDR Mini is adequate for many applications, using the 10 MHz reference from a GPSDO in my home would give the best performance and also allow very accurate frequency measurement experiments.

This platform is very powerful and flexible, allowing all kinds of experiments. It is intended to be used through a computer on a home LAN, so that the Beaglebone Black only plays the role of bridging IQ samples between Ethernet and USB. However, it is also possible to deploy some simple standalone SDR applications on the Beaglebone Black, so that the ground-station can work automatically on its own.

Therefore, there is still a lot of experimentation to be done regarding the software setup. Currently, on the Beaglebone Black, I’m using limetool, by Evariste “ F5OEO” Courjaud, to send IQ samples to the LimeSDR Mini. These IQ samples are generated in GNU Radio on my laptop and streamed through TCP. I have also used simple Python scripts with SoapySDR to generate test modulations.

Besides single-sideband analogue voice and DVB-S2, which represent most of the current usage of the Es’hail 2 transponders, this equipment can also be used to perform very interesting future experiments. Some of these include transmitting very low power signals buried below the noise using spread-spectrum modulation, testing optimized data modems by trying different modulations and FEC algorithms, performing ranging of the satellite by transmitting a PRN modulation through the transponder, doing two-way frequency and time transfer, implementing a TCP/IP connection by using GSE with DVB-S2, etc.

Regarding the rest of the ground-station, I am currently using a 24 dBi WiFi grid parabola for the uplink, but the plan is to replace it with a 1.2 m offset dish with a custom built circular polarization feed for 2.4 GHz. For the downlink, I am using a 1.2 m offset dish and an inexpensive commercial Ku-band LNB modified to use an external 27 MHz reference.

The design motivation for this platform was to have something that would be very flexible to allow many different SDR experiments, and that could be controllable over Ethernet from anywhere in the house. I think this solution satisfies these goals quite well. Some of the difficulties I am facing are related to the spurious emissions of the LimeSDR. Local oscillator leakage and IQ imbalance images can be quite noticeable when its output is amplified to 100W. With some cleverness, things can be arranged so that these spurious signals do not cause interference to other users, or in some situations they could be filtered out.

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Clearly, Daniel is very enthusiastic about the QO-100 satellite and the systems that can be assembled to communicate with it.  A very active Facebook group has many other tips and photos from other members.  Details at:  https://www.facebook.com/groups/252645695661305/  

Walmart & Satellite Communications: AO-91

On a recent Saturday afternoon, April 28th 2018 to be precise, the AO-91 satellite was as active as ever with stations looking to make contact with one another across the Eastern and Central United States.

Walmart #1540 in South Haven Michigan

The AO-91 satellite rapidly passed over the Hyde Park, NY area at over 480 miles an hour which allowed for satellite reception for roughly 11 minutes using a portable antenna called an "Arrow II" and a Kenwood TH-D74 hand held radio which also can record audio. The software used to predict when the AO-91 would pass over my location was the ISS Detector application available on the Android Google Play store.

ISS Tracker application showing altitude, location, distance and speed from
location of K2GOG at time of AO-91 pass on April 28th 2018

Where are satellite users located?

Stations using this and other amateur radio satellites often use a 4 digit grid square identifier to quickly let others know where they are located since it is quicker than saying latitude/longitude, ZIP codes or town names. A grid square that covers the Hyde Park, NY area is FN31 for example.

Grid square boundaries and names in the New York area. Google Earth
with a Grid Square overlay was used to generate this image

Another and slightly more easy way is to use the store number of a Walmart location. Walmart parking lots serve as great locations to operate a portable satellite station since there are few obstructions in the way in most directions horizon to horizon.

Not the strangest thing seen at Walmart

People waving around an antenna in a Walmart parking lots is likely not the strangest thing to see at a Walmart.  Its easy to confirm this by doing a search for "strange sightings at Walmart".  At least if you want to avoid "radio active amateur radio operators", you can predict when they may be at a Walmart by using ISS Detector. Other potentially "radioactive" people are harder to predict at the 24/7 hour Walmart Superstore locations at 1:45 AM!

Frequencies for AO-91

Here is a table of of frequencies to know what to program into your radio

What does satellite communication sound like on AO-91?

Here is a sample recording of contacts being made on AO-91.  How many grid squares, Walmart locations and station call signs did you hear?

April 28th 1:30 PM ET 2018 AO-91 recording by K2GOG

64 Satellites: Can I get a ride too?

T- Minus     10...9...8...7...6...5...4...3...2...1...LIFTOFF!!!

SpaceX was able to put 64 various size satellites into orbit with only one Falcon 9 rocket. The total payload weighed in at 8,800 pounds (4,000 kilograms).

Jerry Buxton, N0JY of AMSAT pictured at the SpaceX launch facility.
AMSAT was responsible for the Fox1Cliff (OSCAR-95) communications
satellite available to amateur radio operators world wide

Payload Details

Of the 64 objects launched on December 3rd,  the amateur radio Fox-1Cliff which is now known as OSCAR 95 is just one of many satellites, so here is the full list of publicly known 60 satellites and basic details, so let's get going.....

Lists: We love lists!

Not every satellite was a "CubeSat" which are normally 10cm cube weighing less than 4 kilograms.The largest satellite part of this launch was potentially the 231-pound (105-kilogram) KazSTSAT Earth-imaging satellite.  

There was also the Elysium Star 2 which carries the remains of Robert Lawrence, an African American astronaut was selected for the U.S. Air Force’s Manned Orbiting Laboratory program.

#1 - AISTECHSAT 2: The second in the AISTECHSAT series and is a 6U CubeSat developed by Aistech to provide thermal images of the Earth. It will also help with maritime and aeronautical tracking as a prototype for a larger constellation.

Thermal imaging system is on board that is used in forest management, fire detection, gathering data for agriculture like identifying the health of the plant, analysing land for expansion. It can also detect energy consumption and loss of buildings.

The satellite also provides airborne and maritime vessel tracking via AIS and ADS-B receivers. The AISTECHSAT can also use a bidirectional communication system on board to send and receive automatic information from the vessel or remote asset worldwide.

For aircraft tracking an ADS-B receiver is on board. HVDN has its own ADS-B receiver that tracks aircraft in the Hudson Valley and is available to its membership. More information can be found here

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#2 - Astrocast 0.1: Astrocast is a planned network of Nanosatellites providing global L-band machine-to-machine (M2M) services. The satellites are orbiting in a low earth polar orbit. This allows the creation of a global network covering the entire globe, including the poles. 

After integration of the NanoLink terminal, the ground based assets can reliably and securely send any kind of sensor data to the constellation of nanosatellites that will acknowledge the reception. Astrocast enables transmission of 1KB/day from any region on the earth.

A geographically distributed network of ground stations collects the data gathered by the satellites. The data are then uploaded to a cloud storage for access by the customer.

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#3 - Audacy:   Audacy is building a space-based data relay network via a constellation of medium Earth orbit relay satellites along with our ground facilities. These satellites will maintain constant connectivity for our customers’ spacecraft from any point on Earth to lunar orbit

Details on 59 more satellites

Fantastic research has already been done by Gunter Krebs on all the other satellites that were part of this historic launch.  Have a look at all his hard work at  https://space.skyrocket.de/index.html 

Add caption

Talk about stuff like this?

Care to talk with others interested in satellite communications and technology plus the experiments conducted up above?   Here are some spots to check out related to amateur radio:

• AMSAT-DL Discussion Forum:  https://forum.amsat-dl.org/ 

• AMSAT DMR Talk Group:  98006 (Listen in here)

• STEM Talk Group: http://stem.hvdn.org/ 

• AMSAT Mailing Lists:  http://www.amsat.org/amsat-new/tools/maillist/maillist.php

• HVDN Orbital News:  http://notebook.hvdn.org/search/label/HVDN%20Orbital%20Channel

First Impressions: Kenwood TH-D74

Sure, I could have posted a review on E-Ham, but rather do that here because I can include pictures and videos.

I have been looking for a new radio to use for satellite, portable and entertainment while enjoying time after a settling in to a camp site.

(The father of APRS, Bob WB4APR enroute somewhere during Thanksgiving)

For my reasons, the Kenwood TH-D74 fit those needs because, as a "current on the market" hand held radio it:

• Provides up to 5W output on 144, 220 and 440 amateur bands in FM and N-FM.
• Has 1,000 memory channels (Like the Yaesu FT-60r does)
• Has built in APRS capability (Like my older Kenwood TH-D7A(g) and a few other radios)
• Has a built in GPS (Only the Icom ID-51, Kenwood TH-D72, Yaesu FT-2DR have this currently)
• Has audio recording capability (saves to an micro SD card)
• Has all mode (SSB, CW, AM, FM) receiver from 100KHz to 500 MHz ( Only the Kenwood F6a has this)
• Has FM broadcast band for music
• Has bluetooth to avoid needing any sort of data cables getting in the way
• Runs on a Lithium battery pack
• Can receive two frequencies at the same time

This radio also is the only other non Icom radio that supports D-Star for digital voice, but at the $589 price tag this radio may push the limits for a ham grade HT and creates a high barrier to entry to new users wanting to try D-STAR.

Its the combination of everything this radio does is what makes it unique and justifies the price to me. Still, I do not know why Icom still treats D-Star as an accessory feature. They must not really believe in it.  Kenwood really needed to jam a lot of stuff into this radio to sell a few at this price point.

If I wanted to carry multiple radios, I would have needed to purchase a combination of radios and other equipment to get the same functionality. Some of those to consider were the:

• Kenwood TH-F6a at $289 because it has 144, 220 and 440 plus an all mode HF receiver
• Kenwood TH-D72 at $350 because it is the best performing APRS function radio available
• Yaesu FT-2DR not sure why, but I like it as a 144/400 and Fusion radio with APRS, but no all mode RX.
• Icom ID 51 at $400 because it is 144/440 with D-Star and basic APRS functions and nice form factor.
• Any DMR capable radio because I like DMR because there are many more repeaters where I intend to be in the US, Canada or elsewhere.

Add in digital recorder plus data and audio cables, software, its gets a little complicated (and more expensive), so does this purchase make sense now? We shall see.

(Programming radio over blue tooth. No wires) 

Satellite Operation

This is actually a short coming of this radio because it is not full duplex, meaning if I am talking on 144 MHz I can not listen to 440 MHz at the same time. The other receiver mutes when transmitting on the other. Operating full duplex via satellite is considered "polite" because you can monitor yourself on the down-link to ensure you are not "doubling" with another userm which often happens on repeaters if your not playing nice.

This is not to be confused with being able to listen to two different frequencies at the same time, even in the same band. The only current production radio that is true full duplex is the Kenwood TH-D72.

Some older popular radios that meet this full duplex criteria are the Yaesu FT-530 and Icom IC-W32 but I already have owned them and I wanted something new. There is the Wouxon UV9D that claims to have full duplex capability but the receiver is desensitized enough to make it borderline usable for satellite use.

As an experienced satellite operator, i can still operate satellite by being "predictive" during a satellite pass to be a good neighbor though. It is easy to program the TH-D74 into split mode so when I transmit on uplink, it will go back to the downlink when I unkey the PTT. I can also put the downlink on one VFO and the uplink on the other VFO.

This is not the same as "full duplex but is close and 100% if I use a second radio to access the FM only repeaters. One nice thing also is that when the TH-D74 is used as an all mode receiver, its perfect as a down-link receiver on the SSB transponder satellites. For up-link, the Yaesu FT_817 works perfect and I have one of those, so now I can work those satellites while portable too!

IMPORTANT: One quick note, I found a "birdie" on 435.160MHz, but its weak. This is where the AO-85 satellite can be found. The IF beat feature is not enough to knock it all the way out.

Clipped to a backpack or belt. NO WAY! 

While I do want to have just "one radio" while doing the aforementioned activities, this is an expensive radio and I want to treat it as such, so will store it in my pack when not in use on the trail, or to just beacon out via APRS where I do not need to press any buttons. A backup radio and for use when I want to operate full duplex on satellite comes in the form of either my Yaesu FT_60 (144/440) or the Radioddity GD-77, which is also a DMR radio. This is what will get clipped to a pack strap.

So, that's whats related to satellite operation. The TH-D74 does have built in audio recording capability so I set this to record on the down link and it logs my QSOs (Contacts) for easy playback or sharing later. This is a really good feature to have for those that do not think I made contact of "oops, I left my recorder at home" or, DAMN! the cable fell out and all I got was a buzz sound" sort of moments. If you are a true satellite operator, you know what I mean!

A word about the recorder feature

You can configure the recorder to automatically record anything on either A or B side of the radio. Not both. I leave this set to B which is the side that allows the all mode receiver to work on. A side only works for the ham bands only.

Perhaps if I hear an interesting HF or SW station, I can record that as well as 144, 220 or 440 activity in the ham bands as well as anything not in the ham bands such as aircraft communications. All recordings are time stamped. There are features to start recording upon voice (VOX) or carrier, which is nice too depending how the squelch is set or tone system in use.

This was another reason I purchased this instead of the TH-D72. Figure the built in recorder is like any of the premium digital pocket recorders on the market, but just for recording radio audio. I guess if I needed to record a note for myself, I could always transmit on a different radio into this one. Ok, maybe....

Recordings get logged to a micro SD card and you can play them back on the radio, or read them on a computer via USB cord or by taking the SD card out of the radio and plugging it into your mobile phone.

(FM scan mode. Can automatically mute when another transmission is heard on 2m or 70cm)

Equalizer & Volume Lock

I have not seen any other review talk about this feature, so I want to say "THIS IS AWESOME"! This is like one of those weird creature comfort settings a 1980's Cadillac would have that you would not need, but was nice to have.

The way this works by going to Menu 963 is where you set the volume (analog knob) to a listening level you like and then you activate this volume lock function. Regardless if you try to increase or decrease the volume, the radio will stay at the level you set until you deactivate the volume lock.

There is also a 6-band RX audio equalizer, a SSB high cut filter, CW filter and 4 band TX audio filter plus 3 stage mic gain. Yes, this is in a handheld radio! Cadillac features indeed! You can toggle the RX or TX EQ on or off, or both and each has its own settings. This makes a big difference when listening on AM or FM broadcast, 2m FM, SWL HF SSB, etc.

These are nice for a few reasons, but will let you discover why this could be helpful at times.

Menu System

Did you see that last section? Menu 963? What! Its well organized. Menu 1-9 are icons, Then you have a list of setting under each of the 9. Then you have sub menus. Its really easy to find stuff to fiddle with and tell someone else how to get there. No more twirling the knob (sorry, that sounded bad) and going past where you need and have to go back the other way. I am not going to look for the politically correct description to go back and edit the preceding sentence.

APRS Related Stuff

The instruction manual will share more about the basic details on certain features, as well as other reviews found all over, even on YouTube. I am going to focus on using the built in bluetooth feature allows you to pair the radio to a computer or smart phone and make use of the TNC as a KISS TNC.

This is nice so that you do not need any sort of data cable to get the APRS data to your computing device running software like UI-View, APRSISCE or others. Also, using this radio with WinLink is possible which could be of interest to EMCOMM/ARES/RACES people. Again, NO DATA CABLE NEEDED!.

Everything else related to APRS works as expected including the ability to append a QSY frequency (short for "can you change frequency?") on one side of the radio when operating APRS on the other side. This is like having the ability to message somewhere on APRS and the person on other end can click a button on his/her radio and bring them to the frequency (including tone and shift) easily. All done without speaking about it. (I thought you said 146.520, I was on 145.620)

All other APRS features work great. Messaging stations, sending location, viewing bearings, etc all fantastic! You can even view weather telemetry data easily.

(Local digipeater which is part of the Red Cross)

How does it sound?

I have never owned an HT that has a mic transmit equalizer (4 band) or a receive equalizer (6 band) Going back to that "Cadillac" comment, this is super nice to have. On transmit there is also a separate mic gain setting (H/M/L). Of the discussions I have had, all have given me positive reports on audio considering its an HT. Yes, with the built in mic.

All Mode Receiver

On HF, there is an internal ferrite bar antenna for the AM broadcast band and up to 10MHz. It works OK, nothing special, but is nice to have for listening to 1130 KHz Bloomberg for updates on economic reporting without needing a special antenna.

It is possible to bypass this internal antenna and use the SMA antenna port to hook in something more capable, especially for HF. When tuning around on 80M, 40M and the SWL bands, its amazing that this receiver does not get easily overloaded, which the Kenwood TH-F6a did as well as the Alinco DJ-X10, X20 and Yaesu- VR_500 HT receivers I have owned in the past. This wont be your every day HF receiver, but its a solid back up.

There is an attenuator to knock back signals 20 dB less and provisions for VFO tuning, fine tuning in 1Hz (yes!) steps. You can use the channel selector knob on the top of the radio or the up/down arrows for even smoother sounding tuning. (Pause for knob spinning laugh) The HF RX is well implemented on this radio and is a fun accessory to have. Another Cadillac comment? Yep.

Imagine being able to listen to the maritime net on 14.300MHz and talk on local 2m at the same time. Nice!

This is ALOT of radio, in a small package.

I set out thinking I would author a differentiated review and that is what I intend to do. After all, an HT is an HT. How much better could it be. Kenwood has done a great job on this radio and is not a mass market entry level radio, so it has a limited appeal to someone who knows exactly what they want. Specifics:

Bluetooth (Built In) 

I really think the bluetooth works well. I can pair it to the 3 different headsets I have and even my car audio system. You use the built in radio PTT to activate transmit if the headset you have does not support tap to PTT and that is ok. I have not used this on satellite operation yet, but not having a wire connecting a headset is something I am interested in trying.

What I do not like, and maybe I have not figured it out yet is not being able to pair two bluetooth devices at the same time. I was hoping to be able to pair to a headset for listening and my mobile phone for APRS mapping at the same time. No luck so far which is too bad.

Also Bluetooth is mono only (I think) not stereo. but thats ok...

Memory & Control

For almost $600 bucks, Kenwood could have charged for software, like Icom who tries to charge for every (damn) little thing. Even Yaesu at times also! Not with this, the software is free to download. I think Kenwood built this into the price of the radio, but hey, free is free. And its not alphaware stuff. Its really nice.

Sort of gimmicky, but Kenwood also has another free software package that allows full remote control of the radio via bluetooth and reminds me of the Alinco-DJ-X10 that has this also. Bluetooth only allows control, not audio pass through which is too bad, but I think its possible and I just cant get that to work. Otherwise, I need an appropriate cable for that!

Last Comments (D-STAR)

I gave D-Star a shot many years ago. Its age is apparent. It needs a major reboot. The server architecture is not good. GMSK, which is what D-Star is based on is not efficient for spectrum use at 6.25Khz wide, you can not put repeaters too close to each other. A single 12.5KHz DMR repeater can be more efficient sicne it is TDMA based. Anyway, I wish Kenwood rolled this out with DMR or could offer a firmware upgrade. I understand the reasons they did not, because the users of DMR are the actual innovators making what hams really want. I think its just a matter of time before a "Big 4" vendor jumps into DMR with a killer radio. Alinco, nice try, but not. 

For how D-Star is implemented, its actually way easier to use than the Icom radios. Figure THAT ONE out!

Closing

I will post some videos and pictures of the radio in action when I find a real world example to show off this radio under real world conditions, so be sure to follow this review thread as I spend more time with this capable radio.