This page is updated as necessary, in order to inform the amateur radio community how to receive and decode signals generated by our projects and experiments. This is particularly useful for upcoming stratospheric balloon launches or other APRS tests. For any inquiry on this topic, please send an email to ham at roinspace dot com.

Next launch is planned for November 22nd, near Stalpu, Buzau, 10:00 local time. Relevant payload details are included below. Flight details are included here.

Another balloon launch is planned also on November 22st, 10:30 local time, by the kids at, using the callsign YO8ENF (UHF APRS and RTTY tracker).

1. Crossband repeater (VHF -> UHF)

  • Consists of a Retevis RT23 portable radio.
  • Uplink: 145.400MHz, CTCSS Tone: 203.5Hz, mode: Narrow-FM.
  • Downlink: 433.800MHz, Transmit power: 1W. In collaboration with RoLink, we are attempting to broadcast the downlink in their network, via a portable node.
  • Please log all your contacts and report them here: (Google Forms).
  • Our goal is to have a rough estimate of ground coverage, as a function of altitude. Please make short contacts, and try to determine your minimum required transmit power.

2. Reprogrammed RS41 radiosonde

  • Consists of a recovered Vaisala RS41 radiosonde, using software by OM3BC.
  • APRS 432.500MHz, callsign YO4ESA-15, rate 2/min.
  • RTTY 434.500MHz (baudrate 50 bps, shift 540MHz, 7 data bits, parity none, 2 stop bits).  FL-Digi can be configured as presented on Rate: 2/min.
  • CW 434.500MHz (identification only), rate 1/min.

3. Custom APRS tracker

  • Consists of an Arduino Nano with LibAPRS, 1W DRA818v and Venus GPS + data logger.
  • 144.8MHz, callsign YO4ESC-12, rate 2/min.

4. (in development) APRS digipeater prototype

  • Microcontroller with 1W DRA818v (VHF) and on-board data storage.
  • Frequency: 144.6 MHz, packet radio (APRS, AFSK1200).
  • Stores all the received APRS messages for later re-transmission.
  • Not included in the October 2020 flight.