Softrock Pages. Initial Configuration.

And some notes about SDR including the "dongles" now available.
More and more are obtaining ready-built SDRs thinking that will save them time and trouble.
Be warned! Setting up a SDR can take more time and be more frustrating than the actual construction.

Transmitting needs a receiver to check you are on the correct frequency and to adjust transmit image rejection. 

Software Defined Radio says it all! Most of a SDR is within the computer.
Because of the wide variety of soundcards, computers, operating systems and the way they are setup there can be no simple "Do it like this" instructions. If you are not familiar with these items you may find you have a lot to learn.
Note many of the pages I refer to contain information for constructors as well as configuration, you may need to look carefully for what you want.

If you go through it thoroughly you will have a better understanding. Most constructors use these pages and get their Softrocks working.
This page is basically a summary of the techniques required.
LINUX:- It is possible to use Linux but I cannot help much with the software side. My main page, link at the bottom, has some references. 


Maybe a single core 2GHz is the minimum, this may need all other applications disabled. Lower performance ones may work but a fast one will not usually need "tuning". I suggest a desktop, these are far more versatile.
The RTL dongle will need a faster computer.


12 volt power and USB if used. For receiving a STEREO line input to a soundcard and speakers or headphones from the output of the soundcard. A GOOD antenna, not just a piece of wire. 
Transmit:- Leave this until you are happy with receiving. In many cases a second soundcard will be required. See bottom of page for some Softrock connections.
Please note the socket marked "Line In" on a Softrock refers to where it is connected on the computer.


Most will work. PCI, USB  and some modern on-board systems are quite good. 
It is not necessary to get a high performance card to begin.
Settings can be very confusing.

Connect to the Computer.

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..

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.
Some notes and links about soundcard settings here.

A simple test to find if you have any chance of receiving is to remove the Line Input lead from the SDR while a SDR program is running, touch the end of the lead and the display should show disturbance.

 The dongles do not use soundcards for an input. The FCD has its own USB, the RTL uses a different method.

USB Softrocks.

First the USB driver must be installed.

On that page the driver and other instructions for manual installation etc appear about one third of the way down.
The installer will install the certificate and then install the driver (32 
& 64 bits) then the hardware can be plugged in.

Then check it with
Initial calibration:- On the "Calibrate" tab click "Calibrate A". (Default startup 56.32MHz.)

Further instructions and links on this page, relevant for all USB Softrocks. 

October 2016. The Softrock and other USB devices use libusb0.dll It has been suggested that there may be problems with earlier versions of this file. If you have problems with USB3 or later versions of Windows it may be an idea to update this file
Windows 10:- It has been reported that the above installation did not work. Another way of installing the driver here.


It is a good idea to get receive working first. SDR# (SDR Sharp) is receive only, see this page also some hints about soundcard setup problems.

If you have a RXTX then learn receive with HDSDR on this page has transmit capabilities. The manual receive IQ adjustment offering an insight to adjusting a SDR transmitter. 

Do not adjust the bandwidth, filters or any other receiving settings until you have got it working. Default settings on all software will give good results.

The dongles need software to be configured specially. SDR# is again the easiest, but read carefully about the RTL.

This page gives basic installation details for  HDSDR a Winrad derivative. This will give receive and transmit capability with all versions of Windows.

CW Transmit, Rocky is good and the easiest, PSDR and Quisk alternatives.
This page shows Rocky, the older versions of this RX and TX software gave problems with current Windows installations the latest, October 2015 version 3.8 should overcome this. Most of the instructions for using Rocky are on it's download site. To add more frequencies to Rocky's drop-down selection relevant to USB as well. Or paste and copy from my list. 

Use one or the other of these programs until you have everything working satisfactorily.

Here is a link to a discussion opened by a beginner, just about everything is covered

Links to other SDR software on my main page, link below.


Basic connections here for a Lite
Basic connections for an Ensemble, this is the VHF one but HF is the same.

Basic Use of SDR Programs

A band of frequencies is displayed on an SDR screen.
The width depends on the sample rate of the ADC used. This may be the soundcard. All will operate at 48KHz, some higher. The FCD is fixed at 96KHz, the new Pro+ up to 192KSPS. The RTL from 2MSPS down. (SPS, Samples Per Second, same figures just a more correct name.)
There are two frequencies to consider, the centre frequency (Local Oscillator) and the tuned frequency.
The centre frequency defines the band of frequencies shown. Do not set the tuned frequency near the centre, always keep an offset.
Because of the way SDR works operating near the centre can give problems. Right at the centre is a dead spot where nothing is received, some soundcards, including the FCD, show a sharp spike there. The RTL shows a big band of noise at the centre in my setup.
Some software hides these effects but does not remove them.

"IQ" Signals

A soundcard SDR is fundamentally a direct conversion system. The problem with direct conversion is that signals both side of the local oscillator (LO) are produced. As an example the Softrock SDR splits the RF signal into two signals with 180° phase difference between them.
Two mixers are used, the LO is split into two signals 90° apart, each of these is sent to a mixer, mixing with the split RF signal. The two signals that come from the mixers are known as the IQ signals, 90° apart. These signals range in frequency from almost zero Hz up to half the soundcard sample rate. Because they have a phase difference the computer can cancel out the duplicate "image" and show a display as wide as the soundcard sample rate with the LO in the middle.
If there is a fault, one of the IQ signals is missing for example, then this cancellation will not be possible and signals will be duplicated each side of the LO.

More of my pages related to SDR

Funcube, beginners use SDR Sharp.

Or HDSDR With HDSDR you must put the DLL in its working folder, use the DLL found here:-
All information is here. Run your mouse over the black header.
If you use Chrome this page translated is good 
SDR-Radio will work with it. I am reluctant to guide an absolute beginner to this software but here is a start

RTL Dongle
Driver installation on HDSDR's site This technique is valid for all software. Be careful! It is easy to assign the driver to the wrong device make sure "Bulk Interface" and/or the correct VID/PID is selected.  See here
With HDSDR you must put the DLL in its working folder, use the DLL found here:-

G4ZFQ March 2013
alan4alan at googlemail com

More of my pages related to SDR

Main reference page:- All aspects of the Softrock SDR a big page with lots of links but you should find answers to most questions. use Ctrl-F on your keyboard to bring up a search box to find keywords.