Model: RT-21dc Category:

Rotator Controller, DC Powered

From $469.00

The RT-21dc is a DC powered version (no AC Mains) of our famous RT-21 Controller. It can be used (with approprate power supplies) with any rotator, it is especially well suited for the Yaesu DC models and Alfa Spids due to their low DC motor voltage requirements.

Perfect for rover/portable operation or fixed station use if you want to save and use your own power supply. You get Green Heron Quality and support, at a value price!

Ideal for Tornado Tuner with GHEveryware Automation too!.


Additional information

Weight 6 lbs
Dimensions 12 × 12 × 6 in
Rotator Type

Yaesu G-800, G-1000, Yaesu G-2800, Alfa Spid, Pro-Sis-Tel 2051/61D, Tornado Tuner, Others (contact us for others)


None, Ethernet LAN (+$89.00), WiFi (+$129.00), GHE Wireless (+129.00)


RT-21 DC Powered Rotator Controller:

The RT-21dc requires an external power supply capable of operating your rotator of choice. We recommend using:
Yaesu model 800, 1000, 2800 DC rotators – Single 13.8 to 24 VDC @ 4A
Alfa Spid, all models – Single 13.8 to 24 VDC @ 4A
TIC Ring – Single 24 VDC supply @ 4A, more if two motors

Higher voltage motors may be accomdated with a separate 13.8V supply < 500mA for the controller, and a higher voltage DC supply (up to 48VDC) for the motor.

AC motor units may be used if a separate source of appropriate AC voltage (isolated from ground) can be supplied.

The RT-21dc can be configured for all of the same position indicator variations as the standard controllers.

RT-21dc Features:
  • PWM speed control effective for most rotator types
  • Precision ramp control for smooth starts and stops
  • Manual control using CCW and CW buttons
  • Point and Shoot knob for set and forget operation to 1º precision
  • The ability to correct for mast slippage using OFFSET
  • Computer control via RS-232 or USB to 1/10º  accuracy
  • Precision heading accuracy up to 1/10thº
  • Master/Slave links two or more RT-21 for stacked arrays or turning multiple systems to the same heading
  • Counter-Rotation for single mast systems with rotator above a rotator
  • Fully programmable settings for speed, ramps, brake delay, limits and more
  • Two alternate OFFSETs for offset antenna directions on the same mast
  • Elevation and EME modes optimize for Az/El systems and tracking
  • Limits rotation for side mounts, and allows up to 720º  total rotation for supporting rotators
  • High contrast yellow-green backlit LCD with 8 brightness levels and auto-dim
  • Many built-in safguards to protect your system from over-rotation due to internal or external failures
  • Rugged .080 aluminum chassis
  • Special advanced options for custom applications
  • Supports “Shortest Route” for rotators with more than 360º  rotation capability
  • Comprehensive SETUP Utility software included
  • Free application software for satellite tracking, and remote control and rotator sharing using standard TCP/IP (Internet)


RT-21dc Specifications:


  • Approx 4” x 8” x 7” HWD
    (Not including rear terminal strip)
  • Approx 3.5 lb – Shipping = 6 lb

Input Power

  • 13.8 to 24 VDC Controller and Rotator
  • Separate 13.8 to 24 VDC for Controller, and up to 48 VDC for Rotator
  • SIngle Supply fuse provided, separate motor power must supply external fusing.


  • High contrast Yellow-Green backlit FSTN LCD
  • Eight brigtness levels w/auto-dim

Front Panel Controls

  • CCW, CW and CANCEL buttons (Operating)
  • SAVE, CHANGE, SETUP buttons (Setup)
  • Point and Shoot knob (340º = full rotation)

External Relay Control

  • CCW and CW DC relay control (12V or 24VDC relays)
  • various configurations

Operating Modes

  • Normal, Master/Slave, Master/Counter Rotate, Slave/Counter Rotate, Debug, Alt Offset

Position Feedback
Mechanisms Supported

  • Potentiometer 150 Ohm to 10 kOhm
  • Variable resistor 500 Ohm (Others accommodated with minor modification)
  • Proximity/reed switch or Hall effect up to 64 pulses/degree (divide ratio  up to 23,500)
  • 2-Bit rotary relative encoder (special order)
  • Others possible

Position Accuracy

  • Up to 1/3º for potentiometer
  • Up to 1/10º with proximity/reed switch

Brake and Reversal Delays

  • 0 to 6 Seconds

Soft Limits

  • +/- 180º from normal stop
  • Restricts rotation to zero or opens to 720º

Motor Speed Control (PWM)

  • 10% to 100% in 10% steps with 10 selectable start/stop ramp settings
  • 100% no ramps  (Relay Control)

Computer Control

  • Compatible with all DCU 1 enabled programs
  • Expanded Ppotocol for GH Tracker and SETUP UTILITY (See manual)


  • User changeable in minutes with no soldering


  • No Motion feedback
  • Pot out-of-range (Pot Systems)
  • Counter Range Error (Pulse counter)
  • Industrial rated Transient Voltage Suppressors on all external terminals

Rear Panel

  • 8 Position barrier strip #6-32
  • Ground stud #6
  • Cable strain relief
  • USB-B
  • DB-9 RS-232


  • Limited warranty, 1 Year parts and labor


RT-21 Set-up Utility:

The RT-21 Setup Utility allows you to manage configuration options and optimize other controller settings from your PC.

It also enables you to . . .

  • Change the vanity boot message
  • See a graphic representation of the rotors rotation range
  • Change the rotors rotation range
  • Modify the security setting
  • Change the NO-MOTION motor timeout
  • Perform Auto-Cal on many rotor types
  • Save rotor settings to files
  • Restore rotor settings from files
  • Test computer rotator control

GH-Setup Utility Chart - Green Heron Engineering

GH Tracker – Satellite Tracking

  • Precision 1/10º automatic control
  • Optimizes your tracking program for the RT-21
  • Interfaces with WSJT, Nova and others

GH Tracker Satellite tracking - Green Heron Engineering

GH Everyware – IP Networking for your GH Controllers

  • Remotely control your rotators over the Internet
  • Share rotators on your network

GH Everyware IP Networking - Green Heron Engineering


RT-21 Documents:


Download RT-21 Brochure


Download RT-21 User Manual




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