juni 2023 – PI4ZLB

Easy Modifications For Inexpensive Radios

Over the past decade or so, amateur radio operators have benefited from an influx of inexpensive radios based around a much simpler design than what was typically commercially available, bringing the price of handheld dual-band or GMRS radios to around $20. This makes the hobby much more accessible, but they have generated some controversy as they tend to not perform as well and can generate spurious emissions and other RF interference that a higher quality radio might not create. But one major benefit besides cost is that they’re great for tinkering around, as their simplified design is excellent for modifying. This experimental firmware upgrade changes a lot about this Quansheng model.

With the obligatory warning out of the way that modifying a radio may violate various laws or regulations of some localities, it looks like this modified firmware really expands the capabilities of the radio. The chip that is the basis of the radio, the BK4819, has a frequency range of 18-660 MHz and 840-1300 MHz but not all of these frequencies will be allowed with a standard firmware in order to comply with various regulations. However, there’s typically no technical reason that a radio can’t operate on any arbitrary frequency within this range, so opening up the firmware can add a lot of functionality to a radio that might not otherwise be capable.

Some of the other capabilities this modified firmware opens up is the ability to receive in various other modes, such as FM and AM within the range of allowable frequencies. To take a more deep dive on what this firmware allows be sure to check out the original GitHub project page as well, and if you’re curious as to why these inexpensive radios often run afoul of radio purists and regulators alike, take a look at some of the problems others have had in Europe.

The Voice Of GPS

Tuning into a GPS satellite is nothing new. Your phone and your car probably do that multiple times a day. But [dereksgc] has been listening to GPS voice traffic. The traffic originates from COSPAS-SARSAT, which is a decades-old international cooperative of 45 nations and agencies that operates a worldwide search and rescue program. You can watch a video about it below.

Nominally, a person in trouble activates a 406 MHz beacon, and any of the 66 satellites that host COSPAS-SARSAT receivers can pick it up and relay information to the appropriate authorities. These beacons are often attached to aircraft or ships, but there are an increasing number of personal beacons used by campers, hikers, and others who might be in danger and out of reach of a cell phone. The first rescue from this system was in 1982. By 2021, 3,632 people were rescued thanks to the system.

The satellites that listen to the beacon frequencies don’t process the signals. They use a transponder that re-transmits anything it hears on a much higher downlink frequency. These transponders are always payloads on other satellites like navigation or weather satellites. But because the transponder doesn’t care what it hears, it sometimes rebroadcasts signals from things other than beacons. We were unclear if these were rogue radios or radios with spurious emissions in the translator’s input range.

The video has practical tips on how to tune in several of the satellites that carry these transponders. Might be a fun weekend project with a software-defined radio.

We’ve seen homebrew satellite devices, but none for an emergency beacon — we aren’t sure what the legal aspects of that would be. There are other satellites that unknowingly host pirate radio stations, too.

Connect and communicate with a satellite via the LEDSAT Digipeater Challenge

LEDSAT Digipeater Challenge - LED orbit The Fly Your Satellite! (FYS) programme, initiated by the European Space Agency (ESA), presents an exciting challenge for radio amateurs and space enthusiasts worldwide to establish communication via the LEDSAT CubeSat digipeater. This unique opportunity invites participants to connect with the ESA Education Office ESTEC Ground Station in the Netherlands through the satellite digipeater, with a chance to win a special prize – a custom QSL card issued by the ESA Education Office and the LEDSAT team. Running from June 26 to July 30, this challenge offers an exciting chance for radio enthusiasts to engage with space technology and demonstrate their communication skills.

LEDSAT: An Overview

Developed by students at Sapienza University in Rome, LEDSAT is an educational 1U CubeSat that participated in the second edition of the Fly Your Satellite! programme. Its primary objective is to demonstrate a LED-based payload for ground-based optical tracking. The successful launch of LEDSAT on Vega flight VV19 on August 17, 2021, marked a significant milestone for the project. Upon launch, a competition for radio and space enthusiasts from all around the world was launched, encouraging participants to record the first signs of life of the spacecraft.

The Digipeater Challenge in Detail

The LEDSAT digipeater is a special feature capable of storing and retransmitting digital messages sent via UHF, serving as a transponder for long-distance communication. Messages can be retransmitted immediately or with an optional delay of up to two days.

To participate in the competition, radio amateurs are invited to send a message using the UHF band addressed to the ESA Education Office ESTEC Ground Station, with the callsign PI9ESA. The digipeater will be activated during specific time windows (see below), and operators involved in the project will be available at the station, “listening” for incoming messages.

Once a message is received successfully, the sender’s callsign and contact details will be recorded on a customised QSL card, providing recognition for their achievement. LEDSAT follows a Sun-Synchronous orbit, resulting in two communication windows each day – around midday and midnight – where it is possible to establish contact. To predict passes precisely above the ESTEC ground station or your area of residence, refer to this link. Additionally, the latest Two-Line Elements for LEDSAT can be retrieved here.

Considering the monitoring and housekeeping requirements of LEDSAT, as well as the potential high demand from operators, the digipeater activation time slots will follow a pattern of one day ON and one day OFF, with the switch-on/off always occurring at 00:00 UTC. This schedule will commence on Monday, June 26^th 00:00 UTC, and conclude on Sunday, July 30^th at 24:00 UTC.

While the challenge is supported by our operators on a voluntary basis, efforts will be made to cover as many LEDSAT passes as possible, especially those occurring around local midday on weekdays. A detailed schedule of passes coverage will be published, please make sure to check this article regularly for updates.

Specific Time Slots for LEDSAT Digipeater Activation

Date	Status	Switch on	Switch off
June 26	ON	00:00 UTC	24:00 UTC
June 27	OFF
June 28	ON	00:00 UTC	24:00 UTC
June 29	OFF
June 30	ON	00:00 UTC	24:00 UTC
July 1	OFF
July 2	ON	00:00 UTC	24:00 UTC
July 3	OFF
…	…
July 30	ON	00:00 UTC	24:00 UTC

Please note that this schedule may be subject to change, so stay updated on any revisions by referring back to this article or additional information provided by the FYS programme organisers on the ESA Education social media channels.

The LEDSAT team has prepared a software package for connecting to the digipeater, along with a user manual available for download on the LEDSAT website. Specific parameters are required to communicate with the LEDSAT digipeater (see table).

Parameters for LEDSAT Digipeater Communication

Parameter	Value
LEDSAT TX frequency (uplink)	435.190 MHz
LEDSAT RX frequency (downlink)	435.310 MHz
Modulation	GMSK
Protocol	CSP + Golay + ASM (AX100 Mode 5)
Baud rate	1200

Important note: If you are not a licensed radio amateur, transmitting to the satellite is prohibited. Nevertheless, you can still participate in the challenge by listening to the messages transmitted by the ESTEC ground station. If you provide evidence of successful reception, including the date and time, you may also receive a customised QSL card.

So, mark your calendars, prepare your messages, and don’t miss your chance to connect and communicate with the LEDSAT spacecraft to receive your QSL card. Let’s unite and make this event a memorable celebration of our shared passion for space exploration and amateur radio communication.

For any questions regarding LEDSAT or the digigpeater challenge, please email cubesats@esa.int.

NASA Team Sets New Space-to-Ground Laser Communication Record

[NASA] and a team of partners has demonstrated a space-to-ground laser communication system operating at a record breaking 200 gigabit per second (Gbps) data rate. The TeraByte InfraRed Delivery (TBIRD) satellite payload was designed and built by [MIT Lincoln Laboratory]. The record of the highest data rate ever achieved by a space-to-Earth optical communication link surpasses the 100 Gbps record set by the same team in June 2022.

TBIRD makes passes over an ground station having a duration of about six-minutes. During that period, multiple terabytes of data can be downlinked. Each terabyte contains the equivalent of about 500 hours of high-definition video. The TBIRD communication system transmits information using modulated laser light waves. Traditionally, radio waves have been the medium of choice for space communications. Radio waves transmit data through space using similar circuits and systems to those employed by terrestrial radio systems such as WiFi, broadcast radio, and cellular telephony. Optical communication systems can generally achieve higher data rates, lower loses, and operate with higher efficiency than radio frequency systems.

TBIRD is a 3U sized satellite payload, meaning it is approximately the size of box of tissues. The TBIRD payload is carried aboard NASA’s Pathfinder Technology Demonstrator 3 (PTD-3) satellite. PTD-3 is a CubeSat measuring about the size of two cereal boxes stacked together. The satellite is synchronized to the Earth’s orbit around the Sun such that it passes over the same ground station at the same times, twice each day.

Achieving the record breaking TBIRD data transmissions truly takes a village. The TBIRD space payload was designed and built by [MIT Lincoln Laboratory]. The payload flies aboard the PTD-3 satellite built and operated by [Terran Orbital]. The PTD-3 satellite was carried into orbit by a [SpaceX] Transporter-5 rideshare mission launched from the [NASA Kennedy Space Center]. The TBIRD mission and concept was developed at the [NASA Goddard Space Flight Center] while the PTD-3 program and mission is managed by the [NASA Ames Research Center]. Finally, the ground station for the data link is part of the Optical Communications Test Laboratory at the [NASA Jet Propulsion Lab].

Of course, future space missions can embed the record breaking optical communication technology demonstrated by TBIRD. Downlinking massive amounts of data from space to Earth is imperative to evolving scientific missions. For example, we expect to enjoy live 4K ultra-high-definition video streaming from the Moon thanks to the Orion Artemis II Optical Communications System (O2O).

Maand: juni 2023