Connecting Soundcard SDR to Computer

And a few notes concerning fault finding Softrocks. Installing and using SDR Sharp and Rocky


The first thing with soundcard SDRs is to connect the audio lines to a computer and set the mixers so signals from (and to) the SDR do actually get there.
A soundcard SDR requires a stereo input. Mic inputs are usually mono, older laptops may only have mono inputs. Newer laptops often DO have stereo inputs (A list started further down.) but do not make the method of swapping between Mic and Line inputs easy to understand.  Sometimes it is just a matter of selecting the Line input in the mixer settings, but maybe it is not called a Line input..
Softrocks Note "Line In" on Softrocks goes to soundcard Line In, it is the RX audio output.
Most cards will work, many are satisfied with what they have. Before you purchase a card especially for SDR do some research, some specifications look impressive but actually offer relatively poor performance.

Install and start a SDR program.

Most SDR programs will replay audio files so you may see how they should work. A few links here Audio Files to Test Software Without a SDR You will probably just want to get on with testing..

An easy to setup receive program is SDR# http://sdrsharp.com/
This does not have an install program so you need to unzip the file and copy the files to a Program Folder, (or, even to a folder on your Desktop.) Then make a shortcut to SDRSharp.exe. (Or just double Click this file.) 

I have dragged the right window border inwards to make the picture smaller and settings panel easily visible. It can be made much wider, and taller, this way.
For a Si570 controlled Softrock make sure the USB is plugged in. All that is needed is to select "Front End" and the soundcard Input and Output you require.
Other settings may be left untouched.
Si570 Softrocks should show the current centre frequency. Change this by typing into the "Center" box - Enter USE " , " COMMA as a SEPARATOR.  
If you have a crystal controlled Softrock select "Other Front End" and type in your crystal frequency in the "Center" box - Enter (Return key). For example 3,778,000
At the moment (February 2012) settings are not saved and need to be reset each time SDR# is started. A good thing for beginners, any mistakes can be resolved by restarting.

"Play" should start reception. Select mode. Drag the grey area to tune, (this extends into the waterfall) use the mouse wheel for fine tuning. Drag the scale to move up/down the band. Type into "Frequency" but this only works within the bandwidth of the soundcard. The up/down arrows move tuning in steps determined by the "Step size".
Si570, move up and down bands by altering "Center Frequency".
Filter width, drag one edge of the grey area, use the arrows or type into the box.

If you get USB instead of LSB, (tuning will also be reversed) tick the "Swap I & Q" box.
"Resolution" slows the display to give better resolution.
"Rate":- Only use rates you know your card is able to support. I think I'm safe to say ALL will work at 48KHZ.

Once a Funcube Dongle has been setup it is a quick way of getting that working.

If the display is not like mine above then there is a problem. SDR# is not connected to the soundcard. The incorrect one may have been selected or another program might be using it

If you have problems look below, TROUBLE?

Winrad is a receive only program that also works with a minimum of settings. I suggest a version, HDSDR, linked, and described, under the first picture on this page http://sites.google.com/site/g4zfqradio/calibrating-the-softrock-si570-usb-controller


For transmit checks another program will be required. It IS possible to use HDSDR (link above) but (February 2012) it has to be done manually, using HDSDR's TX button and the ExtIO PTT button. Note the Return key acts as a crude CW key.

I advise against using Power SDR until your SDR is tested. It has too many settings to confuse a beginner.

 Rocky http://www.dxatlas.com/Rocky/ Version 3.7 is intended to work with internal and on-board soundcards in Vista and Windows 7 but some are finding problems with internal sound.
It will work with USB sound. 
If you have problems go to http://www.dxatlas.com/   get the emal address and send Alex, VE3NEA, a message giving details of your problem, soundcard and operating system.


Rocky:- Select the receive soundcard. I/Q Input for the SDR output. Audio Output for where the speakers are connected. Initially just leave all else. Do not select Transmit.

Crystal controlled SDRs select single band, enter the centre frequency in Hz.
USB controlled Si570s, set as shown.




Start Rocky.

the SDR is correctly connected. Even with no SDR connected Rocky will show a green line on the spectrum showing noise from the soundcard. If you see this then check everything. This page covers most things you may find. 
If the green line is solid with no noise showing then there is a problem. Rocky is not connected to the soundcard. The incorrect one may have been selected or another program might be using it. Perhaps it is incompatible with Rocky, in this case another card may be required. Most cards will work. Any USB device with stereo input may be tried. 

 Enable Transmit and select the soundcard to feed IQ signals to the SDR. Depending on the SDR a COM port may be required for PTT. Softrocks and other SDRs with USB control use USB to set the SDR to transmit.
  Select BPSK31 mode

Start Rocky, the "TX" button should go green. Clicking this should put the SDR into TX mode and send IQ signals to the SDR. The IQ Amplitude is set on the "Transmit" tab in Setup. Transmit setting are described at the bottom of this page  http://sites.google.com/site/g4zfqradio/sdr-with-soundcard-basic-faults


TROUBLE?

If you are not too familiar with Windows sound settings be prepared for problems! Most do not have trouble but some systems can be very frustrating. 

To get a rough check of whether a SDR receiver is working connect phones to the output of it. Tuning through a busy band should produce some high pitched noises that may well sound something like radio signals. Stereo phones should reproduce sound in both channels. If your ears are old this needs care! The high frequencies may not be heard, or maybe just in one ear.

Soundcard settings. Bruce KF1Z
In Windows volume control settings (Properties). XP Right click the Speaker Icon - Open Volume Control - Options - Properties - Recording Input.
First, you must use Line-input to the soundcard. Not microphone input.....
Make sure that in Windows volume controls for input, the ONLY thing that is checked is LINE-IN... [Set the slider to maximum]
If there is a "Stereo-MIX" make sure it's muted.
In OUTPUT [Playback] settings (still windows volume controls)
Make sure the only things checked is WAVE .... (and "master volume" if there is one..) [Set the sliders towards maximum]
Make SURE that LINE-IN is MUTED in playback (output) settings. 
Then you need to make sure the proper card, and line in and out are selected in the SDR software as well. SAMPLE RATE leave at 48KHz. Almost all cards will work at this setting.


To check the soundcard input is correctly selected just feed something into it. Music from a MP3 player, or even just touching the free end of the cable should produce something on the SDR program's display.
The Soundblaster Live! 24 often seems to have a driver bug, it needs the Line In to be 
unselected/selected to work.

Similarly, plug in speakers, or phones instead of the SDR input. When Rocky goes to TX VERY LOUD sounds should come out of both channels. Set the tuning (click on Rocky's spectrum) fairly close to centre, if tuned near to the edge these sounds will be at a high frequency and may not be heard.
 
Signals heard but do not tune:- How to check and avoid an unwanted bypass between the soundcard's Line-In and Line-Out http://www.qsl.net/dl4yhf/speclab/startins.htm#unwanted_audio_bypass   Input to output feedback on Audigy 2 http://www.qsl.net/dl4yhf/speclab/startins.htm#audigy_2  

    LAPTOPS:- THESE ARE REPORTED AS HAVING STEREO INPUTS.
They should be at least adequate for initial testing. Maybe good enough to satisfy..
My ACER 5553 has a stereo mic input and it works great with Rocky and other IQ software
 Neil, G3RIR
My HP NC2400 is stereo too and works well enough to play around with. 
Dave 
kx3dx
I have a Toshiba Equium, that can use the same socket as a Mono MIC input, OR a Stereo Line input. But it's a fiddle to set up, Dave G0WBX.
I am using a Compaq 6910p laptop and it says that it has stereo input.....
My old ACER 1683 gets LIN -IN, LINE-OUT and MIC_IN....Besides that although it is not the best it can work nicely with SR.
 Dell Inspiron Mine is 1 to 2 years old. It has stereo input with mic and line software selected and stereo output. It has 24 bit ADC, but a max sample rate of only 48 kHz
  Fujitsu Lifebook E8420. I works great with Softrock at 96kHz 
 Dell Latitude 610 the docking station has a stereo jack for Line In/Mic In.
ACER D270 NETBOOK, I purchased this for holiday internet access then found SDR worked well. 
If yours is not here look carefully in the manual, if it does not mention stereo input it may not have one. Google the make and model + "stereo input" you will probably find the answer. Dig into the sound control panels.

HARDWARE FAULT?

If you have now found the SDR is not functioning properly then fault-finding will be required.
If it is a Softrock see if Robby lists it here http://www.wb5rvz.com/sdr/ go through the various checks. Commonly faults are due to bad solder joints, bridges or solder splashes. Check with an eyeglass.  Sometimes component values are confused. Check ICs are the correct way round. Resistors should be measured before fitting. A fault causing no reception on RX/TX Softrocks can be due to faulty BS170s, used as switches in the antenna changeover. Bob's drawing of the switching in the PDF.   http://groups.yahoo.com/group/softrock40/files/G8VOI/    Ensemble RXTX PTT fault finding.
One way of testing can be to lift the end of L4 that goes to Q10 Q11. Connect the antenna to the free end.

If you still have problems join the Softrock group http://groups.yahoo.com/group/softrock40/ and ask.
Other SDR kits will have their own group.

TEST EQUIPMENT
These notes refer, in particular, to Softrocks.

TEST EQUIPMENT FOR RECEIVERS 
A minimum of a general purpose TEST METER for voltage, current and resistance is required. Most will use a digital meter. Be aware that some readings will vary between different Softrocks. Readings made where square waves are present, on the dividers and mixer, may vary a lot. 
METER PROBES. Use great care. Do not short out anything when testing a live circuit. Use suitable small tipped probes. Ensure the meter is on the correct range. Current ranges in particular should not be used for testing when voltage measurements are required. 
Also, a GENERAL COVERAGE RECEIVER may help to diagnose and confirm operation.
A SIGNAL SOURCE such as a transceiver running low power into a dummy load can be useful for testing and diagnosis. If not available a simple signal generator or oscillator will do. I use a DDS generator like this http://www.midnightdesignsolutions.com/dds60/index.html I also use one like this http://www.qsl.net/k5bcq/Kits/Kits.html This uses a Si570 so only works above 3.5MHZ unless followed by a divider. A 7474 as in the Softrocks may be used.
OSCILLOSCOPE Robby's construction tests shows the use of an oscilloscope. I do not consider this essential. Indeed unless you are experienced in interpreting what you see they can obstruct progress. Recently someone showed a superb oscilloscope picture of a faulty transmit signal. It was three weeks before someone interpreted it correctly. In the meantime a few simple checks would quickly have pointed to the faulty audio cable.
Very occasionally a scope may help.

TEST EQUIPMENT FOR TRANSMITTERS.
A METER. Note the "PA Standing Current" test can give larger variations than quoted in Robby's pages. This is not considered significant. The specification for these FETs gives a large tolerance for this value. 
A RECEIVER IS ESSENTIAL in order to setup the image rejection. With SDR transmitters this is always a manual adjustment.
A signal source will be useful, as above.
Oscilloscope, same comments as above.