Poor PSK31 decoding with FLdigi

Larry Benoit

I am puzzled by poor decoding of PSK31 signals with FLdigi and DXLabs Winwarbler on my Flex 6500. Generally, any signal less than -85 dBm is mostly gibberish with either digital application. Only very strong signals produce usable copy.

I’ve gone over my settings repeatedly, but have yet to identify any problems.  Here are the system and software configuration parameters:

Computer:

Dell  9000 i7 920, 8GB, Win 7/64 bit with all updates

SmartSDR 1.2.1.49

DAX v1.0.5.49

FLdigi 3.21.81

SmartSDR.xml  version dated 8-MAR-2014

CPU utilization 8-12% average

 

FLdigi configuration:

Capture: DAX Audio RX 1 (DAX RX Audio)

Playback: DAX Audio TX1 (DAX TX Audio)

PortAudio (enabled)

Converter: Medium Sync Interpolator (tried others)

 

SmartSDR settings for digital mode:

 DIGU  3.0 khz (tried many filters, including 100 hz and lower)

DAX button enabled

DAX Channel: 1  (set to peak slightly below 0 db, although I’ve tried lower levels  and have tried other DAX channels)

 

Windows 7 sound settings:

DAX RESERVED AUDIO RX1 (Ready)  2 Channel, 16 bit, 48000 Hz (DVD Quality)

DAX AUDIO TX1 (Ready), 2  Channel, 16 bit, 48000 Hz (DVD Quality)

 

I made hundreds of PSK31 contacts with a Flex 5000A using VAC  and FLdigi and could often get viable copy of signals not much above the noise floor.

 

Any advice or suggestions would be greatly appreciated.

 

73,

Larry KB1VFU

Reggie-k6xr

I may be wrong, but seems like I read that DAX Reserved was not for use with dax? I have never used the reserved features and decode is good.

Reggie-k6xr

checking the notes I copied thisFor each DAX Audio channel, you will see four sound cards.  Let's assume we're looking at DAX Channel #1: - DAX AUDIO RX 1 - DAX AUDIO TX 1 - DAX RESERVED AUDIO RX 1 - DAX RESERVED AUDIO TX 1  
You will connect your 3rd party software to the DAX AUDIO RX/TX sound cards.  The ones marked RESERVED are for internal use in the software so you should not connect to them.  I hope I am reading this correctly.

Richard G7EIX

I am not a user of FLDIGI, but I do recall watching the Video by Greg K5GJ and having a play earlier this year - simple and seamless configuration.

Perhaps worth a watch to see if you have missed something?

https://www.youtube.com/watch?v=lcb5QGoo_Nc&feature=youtu.be

Larry Benoit

Richard and Reggie, 

I initially used the video to setup FLdigi and have re-confirmed all settings.

Also, I inadvertently omitted in my initial post the following Windows sound settings for two additional DAX ports:

DAX AUDIO RX1, 2 Channel 16 bit, 48000 hz (DVD Quality)

DAX RESERVED AUDIO TX1, 2 Channel 16 bit, 48000 hz (DVD Quality)

The FLdigi sound card settings are in accordance with the video -- neither is a RESERVED port.

Thanks for your replies.

73,

Larry KB1VFU

George KF2T

Check your AGC - for digital, I notice it works best OFF, with the slider set just under halfway. Right about the point where you notice the "knee" in noise response.

Larry Benoit

Thanks, George. Unfortunately, I've tried many AGC-T settings, including OFF, with no success.

73,

Larry KB1VFU

Ed_NZ1Q

Larry, I've had a similar problem some time ago. Poor decoding, actually both Rec and Tx garbled (search for my posts). I could not resolve this until I bought a new pc with enough horse-power like yours. However, in your configuration you did not mention if you had a separate video/graphics card. I found that to be key in off loading the processor(s) to allow them to decode PSK properly. SSDR places a high video processing demand on the processor when a separate graphics card is not used.

One thing I noticed was by turning off background processes and using one panadapter and turning the frame rate (in Display) down to 4 or 5, I could get better decode (using HRD DM-780 in my case), but not perfect. You may have tried these things already and may have a good graphic's card too, In that case I don't have any other clues at the moment.

Richard G7EIX

The Dell 9000 came with a ATI Radeon HD 4870 by default.    A relatively poor scoring card by todays standards - but still ranked in the High End Cards on PassMark.

http://www.videocardbenchmark.net/gpu.php?gpu=Radeon+HD+4870

Ed_NZ1Q

Right. I have two NVIDA GeForce GTX-650 in my i5 WIN 8.1 pc.  Works slick in all modes AM to JT-65

Larry Benoit

Thanks for the replies. My machine has a AMD Radeon 5870, a gaming grade GPU with a PassMark of 2610. CPU utilization is typically around 10% with multiple slices, full DXLabs, e-mail, browser, etc.  The i7 920 CPU has PassMark of 5005.

My system is very lean with only essential Windows services running and no crapware, having been previously fully optimized to run PowerSDR at Lowest Latency with no hiccups.  I've never seen any resource constraints whatsoever. Typically, there are nearly 4 GB of free memory.

Running SmartSDR , the machine is not much above idle.  I'm afraid the problem lies elsewhere.

73,

Larry KB1VFU

Neil K2NF

May want to try using only Dax tx1 and rx1 with fldigi, and taking win 7 totally off of the Dax cards and pointing it back to its default sound devices , which are usually microphone and speakers . Also make sure that you or windows are not using any Dax reserved card for any purpose

Andrew O'Brien

I never found any such issues with Fldigi and the 6500, always good copy, same with Winwarbler. Does RTTY  or Olivia have the same issues ?   Have you tried it with a different version of Fldigi?  That should not matter BUT you never know.  There is a newer version than the one you have.   Is this a recent install of SmartSDR and DAX?  Just a wacky thought that maybe a unistall and re-install would make a difference.  Again, no logic to the thought but stranger things have been fixed this way.  Andy K3UK

Larry Benoit

Thanks, Neil and Andrew.

I have confirmed that Windows default devices (microphone and speaker) are correctly configured for the Realtek internal sound card and that no DAX channels are being used by Windows or other devices or applications. I had previously checked these settings, thinking that there might be some spurious noise on the DAX RX1 channel.  Fldigi is the only application using DAX.

Andy, I plan to wait to for SmartSDR v 1.3 for a complete re-install. Hopefully, that will solve this problem.

73,

Larry KB1VFU

Dave - W6OVP

Your reference to https://www.youtube.com/watch?v=lcb5QGoo_Nc&feature=youtu.be  was an outstanding recommendation. It just put PSK31 on my 6300 and on the air in well under a half hour, with both fldigi and digipan!

Whoever cut this 10 minute video (Greg) should be locked in that room with instructions to cut a dozen more such Tutorials on the 6000 series. He really understands what is going through a new users mind, and one of his videos like this one is worth a dozen of anything else. Help (support) like this is what SELLS (and keeps sold) new products.

Andrew O'Brien

I'm puzzled with the many comments in this old thread.  Are you still having problems ?  
Andy K3UK

Larry Benoit

Installation of SmartSDR v 1.3 did not resolve the problem nor did any of the suggestions in this thread. However, it was resolved with a fresh installation of Windows 7 and SmartSDR. It is not clear whether the problem was due to the Windows audio subsystem or DAX. Whatever the origins, it appeared that the DAX stream was becoming subtlely distorted due to corruption of some component or buffer in the audio path. Larry KB1VFU

K1UO Larry

Hi Burt,  Have you ever put in a trouble ticket and have someone from Flex go over everything with you?  Otherwise it appears a complete system reload and fresh start is in order on your particular system.  Too bad but it occasionally is the only way to straighten out a myriad of problems that seem to manifest themselves just about everywhere in the system.

Regards, Larry  K1UO

Tim - W4TME

I would suspect the OS reload may have cleaned up something in the Windows audio subsystem.