Upper Hutt Amateur Radio Club ZL2VH

ZL2VHX Mt Climie 10 GHz Beacon

Branch 63 operates a 3 cm band propagation beacon at Climie for the benefit of the wider NZ radio amateur community.

3 cm beacon antenna

The beacon's oscillator is locked to a 10 MHz GPS locked reference which gives it exceptional frequency stability and accuracy. In addition the beacon outputs both JT4G and CW messages. JT4 is a digital modulation method designed for weak signal reception and the G variant being designed to cope with rain scatter propagation that often occurs on 3 cm.

Recently the Beacon has been received by two stations in Auckland. Not bad for a "line of sight" band!

Design

Feeder losses at 10 GHz make long runs impractical. Therefore it is necessary to mount the transmitter as close to the antenna as practical. The Beacon TX and Power Amplifier are mounted in a separate outdoor unit feeding the antenna via a short length of WR90 wave guide. The beacon low frequency source is being fed from the indoor unit via low loss coax.

Indoor Unit

Located in the South Hut, this generates the modulated 108 MHz, approx +3 dBm signal which is fed via coax to the outdoor box.

Indoor unit with cover off

Components

  1. Trimble Thunderbolt GPS Locked 10 MHz Reference: Provides high stability 10 MHz reference and timing data for the JT4 Encoder
  2. G4NNS RDDS Module: Controls OCXO to generate JT4/CW modulation as well as locking the oscillator to the 10 MHz reference
  3. G8ACE OCXO: 108 MHz Oven Controlled Crystal oscillator

  4. ARDUINO System Monitor/TSIP converter: The Arduino is setup to drive a 4x24 line LCD which is used to display Beacon status information:
    1. Indoor Unit DC PSU Voltage
    2. Outdoor Unit PA Voltage
    3. Outdoor Unit PA Current
    4. Outdoor Unit PA Temperature
    5. Outdoor Unit PA Output level monitor

Data from the Outdoor Unit is sent over two wire RS485.

The Indoor Unit Arduino controller is also used read the TSIP GPS data from the Thunderbolt, converts it to TTL level NEMA message at 9600 baud suitable for the RDDS to sync the JT4G Message.

Outdoor Unit

Components

  1. Kuhne Beacon Transmitter MKU10-bake
  2. DL6AM 8 W Power amplifier
  3. Arduino status monitor
  4. DC PSU

The outdoor unit