USB-8 Relay Board

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  • Use this relay board to switch amplifiers, antennas or other ancillary equipment.
  • The USB 8 Relay Board may be driven using the following methods.
    • Using the band boxes in the USB 8 Relay Board group on the Features tab.
    • Using the Band Data File on the LPT tab.
    • Using the DDRB macro command.
  • Note: → The VFO that has transmit authority is used to drive the USB-8 relay board *UNLESS* the VFO B check box is selected and then the VFO B frequency will be used in all cases.

GUI Controls

Note: There is now a 2nd source for the Denkovi board at a cheaper price called a SainSmart 8. This board is from China and is a drop-in replacement for the Denkovi board.
  • Use Band Data File → Selecting this check box will disable the local auto band following defined in this Graphic User Interface and enable using the Band Data file on the LPT tab.
Note: → See the Band Data file section below for more information.
  • VFO B → Selecting this check box will cause the USB-8 relay board to respond to only VFO B frequencies.
Note: → The VFO B and Use Band Data File check boxes are mutually exclusive and will un-check each other when the other is selected.
  • Band Boxes → Enter a decimal number for each band you want the board to activate a relay for. Entering the following numbers produces:
1 = Relay 1 activated
2 = Relay 2 activated
3 = Relays 1 & 2 activated
7 = Relays 1, 2 & 3 activated
255 = All relays activated
  1. Relays are activated in Binary notation (00000111) = 7.
  2. See the Macro command DDRB for additional programming information for this board.
  3. To use the relay board to band switch an amplifier that uses Yaesu binary notation use the following setup:
  160 = 1   80 = 2   40 = 3   30 = 4   20 = 5
   17 = 6   15 = 7   12 = 8   10 = 9    6 = 10

Band Data File

  • Optionally the Band Data File on the LPT tab can be used to drive the USB-8 Relay Board for enhanced operation vs. the band only operation of the USB 8 Relay Board group settings on the Features tab.
  • To use the Band Data File option follow these steps.
    1. Make sure a properly edited Band Data File is showing on the LPT tab.
      Note: → See this link for more information on setting up the Band Data File.
    2. On the Ports tab take the following actions.
      1. Select the Enable check box in the Parallel Port group.
      2. If not using a parallel port select None as the port number.
    3. On the Features tab in the USB 8 Relay Board group select the Use Data File check box.

Macro Command

Using the DDRB macro command adds another level of control to the USB-8 Relay Board by allowing additional relays to be controlled while still using the Band Data File to switch hardware per band segment.

  • As an example suppose you have an amplifier that uses BCD switching to change bands (Quadra/SPE/others). Additionally, you need to switch in different lumped constants for your Inverted-L on 160 meters for different band segments. Here's how to do it.
 Start     Stop     Data     Macro
 -----     ----     ----     -----
 1800      1899       1        59
 1900      2000       1        60
  • For the first segment 1800-1899 the macro #59 contains this command DDRB128:1;. What this does is combine the the #1 relay (for amp switching) and the #8 relay to switch in a capacitor/coil for the antenna.
  • For the second segment 1900-2000 the macro #60 contains this command DDRB064:1;. What this does is combine the the #1 relay (for amp switching) and the #7 relay to switch in a different capacitor/coil for the antenna.
  • Here is the structure for the DDRB macro command.
DDRB - Sends Denkovi Relay Board a value between 0-255
 Form: DDRB P1 P2 P3;
 Parm: P1 = decimal digit(s) 0 - 255
 Parm: P2 = Separator (1 char {':' recommended})
 Parm: P3 = decimal digit(s) 0 or 1
 Uses: DDRB7:0; Turns on relays 1, 2 and 3 only (suppresses band data)
 Uses: DDRB7:1; Turns on relays 1, 2 and 3 and preserves band data
 Note: Uses binary notation (128 = 10000000 = relay #8)
Note: → See the CAT page for additional macro commands.


  • If you can't get the relay board to work you may have more than one generic FTDI controlled device attached to your computer. Typically, these devices can be an Alpha 9500 amp, a WinKeyer, a USB Hub to name just a few. To see if you have more than one device; open Windows Device Manager and open the Universal Serial Bus controllers topic.
    • With the relay board plugged in you should see one or more entries labeled USB Serial Converter. If you have more than one entry take the following action:
    • Un-plug all devices EXCEPT the USB-8 Relay Board and verify only one device shows in Device Manager.
    • On the DDUtil Feature tab in the USB-8 Relay Board group take these steps.
      • Un-select the Enable check box.
      • Press the Green button.
      • When the serial form opens press the Get Serial # button. If successful there will be a series of eight letters/numbers in the Serial# window and a message will show at the bottom right of the screen. If not successful you should get an error message describing the problem.
      • Close the USB8 Serial form.
      • In the USB-8 Relay Board group select the Enable check box and the relay board should energize.
    • Re-attach your other USB devices.
    • From now on the relay board should energize correctly without having to repeat the above procedure.


  1. DO NOT uncheck the Enable Ser # Address check box on the USB8 Serial form if you used the Get Serial # button procedure. This is how DDUtil knows to use the serial number to open the right device in lieu of just using the first device (index/address 0) in the list.