UHF downlink/VHF uplink Full Duplex Transceiver

Flight heritage since 2016


The ISIS VHF uplink/UHF downlink transceiver is a full duplex communication system for CubeSat TT&C applications. The radio can operate in commercial and amateur bands of the VHF/UHF frequency spectrum and is low power, low mass, and highly configurable, offering the flexibility of changing data rates and frequencies in flight. This radio is tailored for CubeSat missions and cross compatible with other subsystems such as onboard computers and antenna systems. Flight proven since 2016.

Availability: 8 – 12 weeks

  • Features
  • Product properties
  • Performance
  • Configuration
  • Testing
  • Documents
  • FAQ
  • Full duplex communication
  • Data rate re-configurable in-flight
  • Frequency re-configuration in-flight
  • FM transponder mode available
  • Safety watchdog
  • Low power consumption
  • Single PCB radio
  • Single board Telemetry, Telecommand and Beacon capabilities
  • Dimensions: 90 x 96 x 15 mm
  • Mass: 75g
  • Supply voltage range: 6.5 – 20 V DC
  • Power consumption:
    • 0.48W (receiver only)
    • 4 W (transmitter on)
  • Operating temperature: -20 to +60 deg C
  • RF interfaces: MMCX (50 ohm)
  • Data interfaces: I2C


  • Frequency range: 435 – 438 MHz or 400.15 – 402 MHz.. Other ranges available on request
  • Transmit power: 27 dBm
  • Modulation options:
    • Binary Phase Shift Keying (BPSK) with G3RUH scrambling
    • Gaussian Minimum Shift Keying (GMSK) with G3RUH scrambling
  • Data rate selectable: 1200, 2400, 4800 and 9600 bps
  • Data link layer protocol: AX.25 or HDLC


  • Frequency range: 145.8 MHz – 146 MHz
  • Modulation:
    • Frequency Shift Keying (FSK) with G3RUH scrambling
  • Data rate: 9600 bps
  • Sensitivity: -104 dBm Sensitivity for BER 1E-5
  • Data link layer protocol: AX.25


  • Receiver/Transmitter operating frequency
  • Downlink data rate
  • Custom beacon message (AX.25)
  • CSKB connector type and location
  • RF connector position and orientation
  • I2C watchdog implementation

Qualification and Acceptance testing

Test QT AT
Mechanical Shock
Thermal Cycling
Thermal Vacuum
Total Ionizing Dose

*QT is performed on the design/qualification model
*AT is performed on the unit to be shipped

How many output ports are available with these (VHF/UHF) transmitters? For example is it possible to send two modulated telemetries and a beacon through the same card?

The current design has only one RF port intended for UHF downlink transmissions. If more than one RF frequency or RF port is required this would imply more than one card. The device does however offer 4 potential modulation sources to modulate the RF downlink transmission with namely:

1. AX25 Data which can be configured to be telemetry data from the other satellite components or a repetative data beacon.
2. CW or morse code Data which can be configured to be telemetry data from the other satellite components or a repetitive data beacon.
3. A loopback mode where the transmitter is simply retransmitting the audio output from the receiver (assuming a transceiver configuration is used) allowing the device to act as a crossband (VHF up and UHF down) radio repeater.
4. An external modulation input which can be from another modulation source like an other independent modems on the satellite.