© Christoph Petermann DF9CY 2007

Status: This transceiver is working.
Last Revision: 21 September 2009


March 2007: After having collected experience with the Softrock 6.1 receiver, I had the desire to build the transceiver also. So I ordered the SR TXRX 6.1 kit from DJ9CS. So some time after I received it I put all components on the board. I had some problems in getting the oscillator running, but I could trace this back to a wrong placement of one single resistor. After repairing this error, the receiver had been working immediately.

After getting the receiver working I managed to run the transmitter. I had some problems with the appropriate software. The only program I could get running somehow were M0KGK IQ Tools. I get a clean single tone output of 1.2W into 50 Ohms. This is measured with HP8594E spectrum analyser. Any spurious were more than 50db down. This is a very good value indeed.

About building

Again it has been easy building this kit. Everything was inside the bag - nothing missing. You should have some experience in soldering these surface mounted devices (SMD), but that is my job .. I only made some small additions to the original design and wiring described by M0KGK (see diagram below). There is now a selectable input for an external oscillator. I got it working with anxternal drive power of ca 3 dBm (2mW) and you should not go over 10 dBm (10mW). The transceiver can be set to transmitting with a switch at the front panel so you are not dependant on a working keying from the computer COM port. Nevertheless this is working too in my setup.

There is no hardware adjustment needed. The only adjustments to be done are in the software. I have the transceiver running with WINRAD, ROCKY and the M0KGK software.


I have made it working with WSPR and the Softrock TX has been heard in Australia, New Zealand, Mauritius, United States, Canada, Brasil and elsewhere. That is thrilling. A first PSK31 QSO was successfull with only 300mW of output.

I could modulate the transmitter with a DRM signal out of the DREAM DRM software. This gave excellent signal quality over a few meters.

Latest information

I had to change polarity with the I/Q signals on the input AND the output because PowerSDR software cannot do this by softswitch. With WSPR I get about 1w of output. It is fun to work with Softrock on 40m.

I have rewired the DB9 socket for operation with PowerSDR. See the manual. It is valid for VE3NEA Rocky as well (also described on that site).

Link to the software setup: DF9CY - Softrock Version 6.1 RXTX Software Setup

All other information you may get from the internet publications. Especially mentioned here is the SR40 Yahoogroup ( see link below ).

Here is a Pile-Up on 40m on the evening of 14 June 2007 with a bunch of stations calling the expedition station 3B7SP, which was audiable a little bit above 7020 kHz too without any problems. Switching to my TS690 I found it to be about the same quality. The program running was Winrad 1.25 and the soundcard used a Creative Soundblaster external 24 Bit / 48 kHz.

Some views of the Transceiver

Peripheral connections diagram.

DF9CY wiring diagram. This is valid for PowerSDR (all versions) and Rocky by VE3NEA. If you do not need the paddles for CW then use the red wires only.


DJ9CS : SoftRock: Ein Einstieg in die Technolgie des 'Software Defined Radio' (SDR)

Softrock YahooGroup