QIKCOM-2 - The first APRS TouchTone Satellite
Bob Bruninga, WB4APR, Instructor US Naval Academy, (last name at usna dot edu)
Midshipmen students: Skinker, Segalla, Hunt, Diasordaz
Flight unit #2 delivered 18 Nov 2015 to the spacecraft integrator. Unit #1 is being held as a hot-backup but will be looking for a launch opportuniy once the first flight unit is launched. All we need is about 5W of power and a place to bolt onto. It contains its own deployable 19" thin wire whip antennas that you can see here coiled up and sticking out the left end of the module.
QIKCOM-2's significant payload is the APRStt (TouchTone) relay system: Using simple radios with Dual Tone Multi-Frequency (DTMF) keypads allows many more SATCOM users to experiment with space than only those with the more expensive radios with built-in SATCOM APRS modems. There have been several iterations of this system in APRS over the years since 2001, but this will be the first one in space and will help introduce amateur radio operators everywhere to this unique capability bringing APRS to any user with any walkie-talkie, not just those with APRS modems in their radios. Read more about APRStt. To use the spacecraft with your DTMF mobile or handheld all you have to do is store your callsign in DTMF memory using this DTMF Callsign Encoder.
This QIKCOM-2 transponder is to join a number of Networked APRS transponders operating in the Amateur Satellite Service that are, or will be, on Orbit in 2016 and all will appear on the live APRS satellite downlink page and ISS downlink page:
PCsat-1 in orbit since 2001 semi-operational
ARISS on the ISS since 2007
Psat Operational May 2015
BRICSAT-1 launched with PSAT, but insufficient power budget
QIKcom-1 with terrestrial APRS alert beacon on ISS, but activation blocked by FCC SNAFU
QIKcom-2 with APRStt for launch Summer 2016
PSAT-2 To be Launched spring of 2017
BRICSAT-2 To be Launched spring of 2017
ASTARS missions: Prior APRS missions on other spacecraft, ISS, Shuttle and MIR
OVERVIEW: . The QIKcom-2 module is being built by a group of students at the Naval Academy and has been offered a ride to space on a host satellite named eXCITe to be launched in February 2016. The rendering (upper right) shows how QIKCOM-2 attached to a NovaWurks universal adapter plate for rapid assembly and integration. The image at right shows how it might appear attached to a spacecraft made up of highly re-configurable modules. This eXCITe mission is a longer life mission than our previous very-brief QIKcom-1 flight opportunity which will be deployed from the ISS and probably last only a week or so due to its host's high drag. In contrast, QIKCOM-2 will hopefully have a several year life as it and eXCITe will be deployed from the higher altitude SHERPA spacecraft.
QIKCOM-2 continues the PCsat(2001) and PSAT(2015) missions noted above containing an APRS packet radio communications transponder for relaying remote telemetry, sensor and user data from remote users and amateur radio environmental experiments or other data sources back to Amateur Radio experimenters via a global network of internet linked volunteer ground stations. The APRS transponder also includes telemetry, and some command and control for the user modes. QIKcom-2 also adds a unique experimental DTMF uplink on 145.98 MHz for users in the field who might not have access to an APRS radio.
Operations under ITU Rules: QIKcom-2 operates under the ITU rules of the Amateur Satellite Service. Although it is flying attached to, and powered by, a host spacecraft, its mission and functions are entirely amateur radio related and fully fit within the QIKcom ITU RULES. It is operted under the license of the control operator WB1HAI in Annapolis.
QIKcom-2 FEATURES: Again, due to the short fuse, the QIKcom-2 payload will be an APRS digipeater similar to other APRS satellties but will add an APRStt (Touchtone) module to allow users without APRS capable radios to have the same type of APRS data reporting. APRStt uses DTMF for sending callsigns and grid squares and the spacecraft acknowledges the uplinks by voice response. DTMF users may also send any of 99 pre-stored messages (including all the standard ARL radiogram messages) by sending the message number. QIKcom-2 also converts the DTMF data to a packet in APRS format so that all APRS users can also see all the APRStt users and their data also goes into the global APRS system. Here are some of the Voice Responses to DTMF uplinks:
APRStt GRID MAP Encoding: The map table below encodes the 99 grids that have 99.99% of the worlds ham population into only 4 digits by converting the first two letters into two digits from the 00-99 table. You can see that our Maryland FM19 grid becomes 1819 in DTMF.
DTMF Callsign Encoding: QIKCOM-2 also cleverly compresses a 6 character call into only 10 digits following the 4 digit grid noted above. The first six digits of the call are the matching single keys for the callsign letters, EG: 924227. The next 4 digits encode the 2 bit location of each of the 6 call letters on each of the 6 keys used. For example, the 6 letters of WB4APR on the 6 keys are key locations 120112. Since each location is between 0 and 3, they can be encoded in 2 bits each (powers of 4) and assembled left to right into a 12 bit binary number. To convert to decimal, take the first 2 bits times 1024, the next 2 bits times 256, the next 2 bits times 64, the next times 16, the next times 4 and the last 2 bits times 1. Then add them up and get the 4 digit decimal "key code" (1558 in this example). This 4 digit decimal number we call your callsign key code. For those that are 12-bit-challenged, Bob Wood WA7MXZ has written an DTMF Callsign Encoder to do this 4 digit number for you. For shorter calls, right-pad to 6 with spaces. A space is encoded as the "0" key with the key location code of 1. The entire Grid and call report adds a "*" at the beginning and a "#" at the end for the full 16 DTMF key report.
DTMF Robustness: The combined 16 key combination is then stored in the DTMF memory of the users radio so that it can be transmitted in a single 3 second burst. Since the entire code is self contained, is always 16 keys, is sent at a standard speed, always begins and ends with known keys and all keys inbetween are decimal only, then any other combinations will be ignored. Also the usual failure mode of DTMF is duplication of digits or omission of digits which will be ignored by the mentioned constraints. A successful uplink will be ACK-ed by voice since the DTMF user cannot see the APRS downlink.
DTMF MESSAGES: The DTMF decoder will also accept an encoded standardized 2 digit message number (00 to 99) to select any of the 99 preloaded messages on the spacecraft. These messages are the standard ARL radiograms plus some other special ones (such as 41 for a QSO) for this satellite. To send one of these messages in the same 16 key DTMF memory use the following format. This is a 16 key DTMF string that begins with the "C" key to indicate a message, and then a 2 digit message number and then a 2 digit modifier xx, followed by the above encoded CALLSIGN. If the message is an actual ARL Emergency message, then the modifier should be 99 and the speech will include the word "EMERGENCY". If the modifer is anything over 90, then it will not say Emergency but will say TEST. If the modifier is less than 90, then the modifier will only be used if the template for that message has a blank in it for insertion of the modifier.
The "C" DTMF key indicates a message. The "MM" digits indicate the two digit message number, the "xx" digits are a numeric modifier that will replace any "_" blank in the messge text. Then the remaining CCCCCCxxxx finish off the transmission with the full encoded callsign as in the grid format.. See the Actual Flight list of messages and for background the standard ARL radiograms and a copy of the Maritime Emergency Codes that are also included.
Making a Contact: When you send your grid and call by DTMF the spacecraft will say "GRID FM19 from WB4APR, QSO number xx". The QSO number increments with each new station up to 99 and rolls over. To complete a contact with such a grid, send message number 40 (see below) with the QSO number xx. The spacecraft will say W3XYZ says message number 40 QSL your QSO number xx, my number is yy" to complete the contact. Of course, an APRS copy of each of these messages will also come down on the downlink for those with APRS radios. Since the QSO number will change with each contact, you can manually enter just Bxx and then hit another DTMF memory that has the remaining portion of the message and your call 40CCCCCCXXXX# to complete the QSO for a new QSO number. With practice you can do this rather quickly. Notice that this special "B" message format is slightly different from the "C" format in that the order of the MM message number and xx modifier are reversed so that you only have to manually enter the three keys "Bxx" to send this special QSL message.
Operations in the Amateur Satellite Service: The transponder and beacon on PSAT are operated in the Amateur Satellite Service to encourage amateur radio students, educators and experimenters around the world to contribute additional satellities to this constellation on 145.825 MHz or to build interesting self motivated remote sensors suitable for the uplink channel. See our ocean or bay oceanographic data buoys for examples. This kind of Amateur Radio experimentation fits well in the ITU rules (see Psat justification) for operating in this service and well serve our educational and outreach goals for student projects encouraging young people to be interested in Science, Technology, Engineering and Math.
The QIKcom-2 System (prototype) shown above, is composed of the same Antenna-Release and Electrical Power System (EPS) board flown on QIKcom-1 plus the new Byonics.com version of the MicroTrack-4 with 10 Watt transmitter (tuned to 4W) and their Micro-DTMF receiver we use to implement the APRStt functions. The larger photo is the DTMF and Speech system board using the Parallax Basic Stamp CPU translator, Speech synthesizer (Speak-Jet), and text-to-speech processor (TTS256). The labels refer to notes on the Engineering unit (shown) that need to be corrected on the Flight Unit. The image at right shows the Engineering unit delivered 4 June 2015.
QIKcom-2 Operations: Like all the other APRS satellites, QIKcom-2 will support live APRS users on the global space frequency of 145.825 half duplex. In addition, it will listen on 145.98 MHz for the DTMF users. The DTMF users Grids and calls will be converted to both voice and APRS grid formatted packet and combined with other APRS user packets on the 145.825 downlink. The DTMF users may also send any of the standard numbered ARL radiogram messages. All users are expected to follow the procedures in the QIKcom-2 User Service Agreement. That is, live operation only, and APRS packets or DTMF attempts no more than once every 30 seconds (or as indicated in that document).
Narrow Band Operation Required: Unfortuantely, the DTMF VHF receiver we are using was not made for space and so it is not very tollerant of high deviation and doppler. This is a problem, but it is the only receeiver we could get on our schedule. There are several ways to mitigate this problem for DTMF users.
Global Experimental Data Channel: QIKcom-2 is the 7th APRS data transponder in this initiative to encourage both new satellite construction in support of this experimental data channel and lower cost student buoy and remote environmental sensor experimentation at other schools. Other APRS transponder satellites are welcome on this frequency. When we have ten such transponders in orbit we can pretty well guarantee coverage within an average of about 10 minutes almost anywhere on Earth.