Saturday, February 13, 2010

Softrock and the Digital Modes

Today I was experimenting with setting up PowerSDR-SR40 for use with fldigi and other digital software, and I got everything talking to each other.  When everything is working together, it makes operating digital so easy.  So far, I got PSDR working with fldigi and Ham Radio Deluxe.  I'm planning on getting it working with MMSSTV and EasyPal Digital SSTV program.  I dont think there will be any problems, as they should set up the same as the ones I already got working.

There are 2 programs you will need in order to make everything play nice.  First is "Virtual Audio Cable". it can be downloaded from here:

When you get it, you will need to create 2 virtual sound devices.  There are good instructions at the above website on doing this.  One will be needed for receive, the other for transmit.

The other program you will need, and you will only need it for software that also controls the radio, such as fldigi and Ham Radio Deluxe, and that is "com0com", This creates virtual com ports to link the control aspects together.  It can be gotten here:

You will need to create 1 pair of com ports for most applications.  There are excellent pdf directions on how to do this at the above website.

Then go into Powersdr and set up the "CAT" section.  Although some software will work using the identifier set for "SDR-1000", I've had better luck setting up emulating a TS-2000.  Under CAT control, set the com port as the lower com port number that you created in the virtual com ports, I used COM5. Fldigi will use COM6 under its CAT settings.  I used RIGCAT in Windows to control the SDR, and it plays nice.  I have had some problems getting the external programs to control PTT, so I just use VOX for that.  I used to use VOX in my Yaesu too when I ran digi modes.

To get audio to the programs, you need to set up virtual audio cable.  I used Virtual Audio Cable #1 for audio out from PSDR and VAC #2 for the TX input audio.  These settings will be found in the VAC tab in the audio settings in PSDR.  The audio settings in fldigi are just the opposite - VAC2 is the output device, and VAC 1 is the input.

Once everything is talking, fldigi will read the frequency of the radio and you can then use the logger in fldigi, and it works like any other radio would with CAT control.

Ham Radio Deluxe sets up in a similar fashion.

To listen to your receive audio, should you choose to do so, VAC has a little utility called an Audio Repeater.  You can set that up to input the proper VAC device as the input, and your soundcard that you use for your speaker audio as the output of the repeater.

There you have it, a basic overview as to how to set up different software so they will talk to eachother.  Once they talk, operation is a breeze.  I worked a little bit of the RTTY contest, and worked about 25 contacts in less than an hour with only 15 watts of TX power.

Good luck, and I hope this helps you get things working with your Software Defined Radio.

Tuesday, February 9, 2010

SoftRock v6.3 RXTX+Xtall

About 2 weeks ago, I finished building a SoftRock v6.3 RXTX+Xtall SDR transceiver.  I ordered the transceiver and  3 power amp, low pass TX filters, so I can cover 80 meters thru 10 meters.

The 6.3 TXRX is a 1 watt PEP transceiver capable of running whatever frequency bands that you supply PA's for.  The standard kit allows for 16 presettable (with a 4 section DIP switch) frequencies.  Each frequency is tunable over  a span of 96 KHz with the software, with the preset dip switch setting being the center of that tuning range.  All modes are possible, including SSB, AM, NB FM, and all of the digital modes, including Slow Scan Television using outboard software.

Most of my operation so far has been on WSPR on the 40 meter band, however I have operated SSB on 20 and 40 meters, and have worked a couple of countries using an outboard HFPack amplifier at about 15 watts.  The performance is nothing short of remarkable, and have gotten exceptional audio reports while using a VERY cheap computer microphone.

Operating an SDR transceiver requires the use of 2 different sound cards.  I use one card that works as the digital signal processor for the radio and the other to drive the speaker on receive and mic for transmit.  For the radio card, you want the best sound card you can get, with the lowest noise and highest sample rate.  92 khz sample rate cards are available with noise floors in excess of -100 dB, and they are common and inexpensive.  I bought a Soundblaster Audigy card for this purpose, but with many soundblaster internal cards, there is some phase shifting in the card, and I couldnt get a good balance without setting the phase and amplitude all over the place.  I've used an older USB card such as the Soundblaster Live external card and that works pretty well.  The external cards apparently do not suffer from the phase shifting that the internal cards do.

With the bare transceiver with the fixed frequency settings, the only software that is useable with it is a special version of PowerSDR, called;PowerSDR-SR40 and is available at  All other versions do not allow you to transmit if the fixed frequency is enabled.  There is, however an add on module that allows USB control of the Si570 oscillator that allows continuous tuning, which I ordered but have not received yet.

I will write more stories on this radio, and will detail a little more precisely on setting up this radio for use.  It is a fun little rig, and for roughly a $100 investment, you will have yourself a very capable little radio.

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