External Connections Introduction


To connect the Softrock Lite V6.2 to the outside world, you will need to provide three connections:

(go directly to build notes) (go directly to build notes)

External Connections Bill of Materials

External Connections Summary Build Notes

External Connections Detailed Build Notes

Top of the Board

External Connections Top View

Install Power Connection

  • Connect DC power leads to the pair of plated through-holes just below D1 on the left edge of the board.
  • The plated through-hole nearest to D1 is the positive connection to a DC power source and the lower of the two plated through-holes is the power supply negative connection or circuit ground.

Install Power Connection photo

Install Soundcard (I/Q) Connection

A stereo audio cable may be connected at this time to the board at the three plated through-holes along the lower left edge of the board near the lower left corner.

  • Use a short piece of #22 bus wire to connect the middle plated through-hole (ground) to the shield (barrel) of the cable and wrap the end of the bus wire around the outside of the cable several turns for strain relief of the cable.
  • The tip of the stereo cable plug connects to the plated through-hole that is marked with the letter T on the board
  • The ring of the stereo cable plug connects to the plated through-hole marked with the letter R.
  • The 30m, 20m, and 17/15m kits use 1/3 sub-harmonic sampling. This results in the I and Q signals for those kits being reversed. Consequently, if you are wiring the connections for one of these higher band kits, reverse the preceding wiring instructions. The photo below shows the wiring for the lower band kits.

Install Soundcard (I/Q) Connection photo

Install Antenna Connection

It is extremely important to use an antenna with as close a match as possible to 50 ohms impedance. The radio's sensitivity is predicated on a 50 ohm antenna input.

  • Connect a length of 50 ohm coax to the antenna connection on the right edge of the board near the upper right corner.
  • The upper of the two plated through-holes is the antenna return connection to the coax shield
  • The lower plated through-hole is the coax center conductor connection.

You may want to review the series of messages on this subject in the Softrock 40 Yahoo Group.

Additionally, you should review the materials on the Clifton Labs website concerning the use of an antenna isolation transformer

Finally, regarding the "floating antenna RET" connection, review the messages in this topic where the builder was getting no signal and the cause was the improper ANT RET connection.

Install Antenna Connection photo

External Connections Completed Stage

Top of the Board

View of Completed Top

External Connections Testing

Radio Test - Generated Signal

Test Setup

The Softrock is ready to receive now. The first test, before connecting to an antenna for off-the-air signals, is to set up Rocky for 40m operation, connect the I and Q outputs to the stereo input of your sound card, and inject a signal into the radio's antenna terminals

Rocky setup and download instructions are available on the Rocky website

  • Set up a signal source (the author used the the Norcal S9 Signal Generator) to generate a 50 uV, 7.040 MHz signal into the antenna lead.
  • Run Rocky 3.2 with the center frequency set to 7.056 MHz.
  • The results are as shown in the graphic below.
Radio Test - Generated Signal