HDSDR and Fldigi

Using Fldigi with HDSDR and SoftrocRXTX Radios                                                            

 Original document modifieand expandeby Wes Hartman, KC5FGK. Used with permission of Brian Lloyd, WB6RQN/J79BPL.



These instructions have beetested on Windows 7. Please note: this is my working configuration. Other hardware/software-variants for VAC and VSPE are possible.







VAC configuration


VSPmgr configuration


HDSDR configuration


Install fldigi








Downloaall the software pieces you need.


•    The ConFiG SoftRock tool (CFGSR.exe).

•       HDSDR.

•       Fldigi, latest version.

•     The Kenwood TS-50  rig description XML file for fldigi'RigCAT.

•       VAC v4.09, release version, not the demo version.

•     VSPmanager.


Install the ConFiG Softrock tool.


Download the latest version (2.6 at this writing). Follow the instructions athe link above.


Install HDSDR.


Download the latest version (2.14 at this writing). Install using the defaults. Thecopy the ExtIO_Si570.dll file from the CFGSR installation directory to the HDSDR installation directory.


Install VAC.


Follow the instructions provided with VAC. There are some differencebetween installing with XP, Vista, and Win7 so be sure you read the instructions, most notably in how to deal with unsigned drivers in Vista and Win7.


Note: you MUST use the purchaseversion of VAC 4.09. You MUST NOT use the demo version! Go ahead and buy it. It will work.

VAC configuration


Open the VAC control prograControl Paneand configure VAC.


You get to the VAC control panefrom the Windows "Start" button under "All Programs". Look for the "Virtual Audio Cable" menu iteand then selecControl panel.


In the upper left hand corner of the control panefor VAC you want to seifor cables. I lefall the other settings alone. Click the "Set" and "Restart" buttons. If you want to check, here is what I have all the VAC parameters sefor:










Max inst


Ms per int


Stream format

"Cable Range"

Volume control


Connected source lines


Clock corr %



Once you click the Restart button you should see cable and cable 2 appear in the lowesection of the Virtual Audio Cable Control Pane(if not sooner).



VSPmgr configuration


Now set up VSPmgr.


For now you will create a single port-pair that will be usefor CAT control of fldigby

HDSDRBoth rig controand PTT will be handleby this single port-pair.


Start the VSPmgr utility. It will show you your physicaserial ports and offer to create a virtual port pair. Make sure that your virtual port pair starts above any possible physicaserial port numbers. It is possible for virtual ports to conflict with physical ports if the physical ports aradded later. Imy case I created port pair COM7/COM8 for communications between

HDSDR and fldigi. Most of the examples use COM6/COM16 or COM7/COM17 but I

discovered that some programs, e.gWSJand WSPR, have problems with port numbers above 8. Thereforecreating a port-pair where botCOM numberare below 9 means that the configuration may be used later on to communicate with these other programs.


Setting up the port-pair is nothing more thaselecting the desired values for End 1 and End

2, COM7 and COM8 in this caseand clicking the "Create Pair" button.



HDSDR configuration


To set up HDSDR to use VAC, start the HDSDR prograand click on Options [F7] to choose the following options:


•    Select Input  > Softrock Si570 and MME (16 bit) drivers

•       SDR TX Suppor(checked)


Click on "Soundcar[F5]" to select your connections for your Softrock installation. For the interface to fldigi, select Line 2 as the “TX Input” and Line 1 as the RX Output.

After making your selections, click OK. See the figure below for my settings:



Nexclick the “Bandwidth [F6] button and select your bandwidth sampling rates. Imy case,

96000 for both Input and Output. It may be possible to set the output sampling rate as low as

12000 to reduce the CPU loafactor.




Set up CAT in HDSDR.


After you have set the above values, click on Options [F7] to choose the following options: CAT to HDSDR

•     Port  > 1st port in pair created with VSPmgr (i.e. COM7)

•       Baudrate (bps) > 57600

•       PTT activation pins  > none (CAT only)

•       Make sure Mute Raudio on TX” and “activated” are checked


Click the “Star[F2] button and you should see the spectrum and waterfall areas activate. This completes the configuration of HDSDR to use fldigi. Now we setup fldigi itself.

Install fldigi


(This document assumes that you are running fldigi on the same computer that is running

HDSDR so that means you have installed the Windows version of fldigi.) Install the RigCAT XML description file for Kenwood TS-50 transceiver.

On Windows, fldigi keeps its configuration files in the fldigi.files directory (folder) in the user's home directory, i.eC:\Users\<username>\fldigi.files\rigs (assuming Win 7)Place the RigCAT description file for TS-50, i.e. TS-50.xml, into the rigsfolder. Note: in Windows 7, you must

run FLDIGI.exe first to be able to see the rigfolder.


Starfldigi to perforconfiguration.


You may gean error message because the audio input has not been selected. Jusdismiss any error messages. Click on the "Configure" menu item to perform the configuration


process for fldigi. It will offer you several options. It doesn't matter where you start but you need only configure "Sound Card" and "Rig Control" to get fldigi working with HDSDR.


Clic"Sound Card" to start the configuration of fldigi to use VAC to communicate with



The "Fldigconfiguration" window will pop up with the "Audio" tab selected. If the

"Devices" sub-tab is not selected, select it.


Click the "PortAudio" selection button if it is not already selected. For "Capture:" set "Virtual

Cable 1". For "Playback:" set "VirtuaCable 2".


The waterfall should come alive just as soon as you set the proper virtuacablefor input and output. Imy case that didn't happen. I found that I have hatrouble with fldigi getting the sample rate correct when in "Auto" or "Native" mode. Ifyou see the following error message"PortAudio error: Invalid sample rate," click on the "Settings" sub-taand set both the Capture and Playback sample rates to 48000 to match the setting for VAC in HDSDR.


As long as you are at the "Settings" window for "Audio" you cacheck the following:


For the sample rate converter ("Converter") set "Medium Sinc Interpolator" if it isn'already set. Corrections should all be set to zero.


Set up RigCAT to control HDSDR and vice-versa.


Click the "Rig" tab at the top of the configuration window. Fldigi supports severaways to communicate with your rigWe are going to use RigCAT. (Hamlib works too but I am not going to cover that.)


Click on the "RigCAT" subtab to bring up the RigCAT configuration window.


Click the "Open" button next to the "Rig description file:" box. That will let you select the proper rig description file. Navigate to the rigs folder if not already there anselect "TS-



Below that are some timing settingfor communication betweefldigand HDSDR. These are influenceby the speeof your computer. I use the following:






Retry interval


Write delay



If you geerror messages from fldigi about communications failure with the rigtry increasing the Write delay and/or Retries. If you notice that the response time is too long, i.efrequency changes in HDSDR or fldigi take noticeably too longto be reflected in the other program you can try reducing the delays.


In "Device:" select the 2nd port in pair created with VSPmgr.


Click the radio button next to "CAT command for PTT" and VSP

Enable. Go back up to the top anclick the check-box for "Use RigCAT". Now click the "Initializefolloweby the "Save" buttons.


If rig control is workinyou should see the VFO frequency for HDSDR appear in the frequency display of fldigand RigCAT – TS-50 directly above. If you tune HDSDR, the frequency display of fldigi should automatically follow. If youclick the "T/R" button near the lower right side of the fldigscreen, HDSDR and the Softrock radio should key up. These two tests confirm thaRigCAT is working.


Set the "SweeSpot" so thafldigi works properly with the click-tune function of HDSDRClick on the "Misc" tab at the top of the configuration window. Click on the "SweeSpot" sub-tab.


Set the CW value to the frequency of the CW note you useSet "RTTY" an"PSeal." both to



Click the "Save" button.


Set the operator and QTH info.


Click on the "Operator" taat the top of the configuration window and fill in the information. When doneclick the "Save" and "Close" buttons.


At this point, fldigand HDSDR are set up and should be working together. There are quite few other things thacan be set up in fldigi to suit your operating preferences but that is beyond the scope of this document. Refer to the fldigi manuato see whaall the other functions do.

Original document modifieand expandeby Wes Hartman, KC5FGK. Used with permission of Brian Lloyd, WB6RQN/J79BPL.