Transmit audio distortion with 8 active panadapters and slices (6700 & V1.1)

Keith - AE5XN

I'm noticing some distortion/cutouts in my transmit audio when monitoring with another receiver whenever I have the full 8 panadapters and 8 slices active on my 6700, running SSDR V1.1 under Windows 8.1 Pro.  Here's how I can always duplicate it:

1) Open 8 panadapters and 8 slices (can be any band, any mode).

2) Select one of the slices to transmit on, and then proceed to transmit voice audio (SSB or AM, doesn't matter), and monitor the transmitted signal audio on a separate receiver.

3) I notice what sounds like intermittent clicking/cutout on the transmit audio, regardless of output power level (1W to 100W), while transmitting into a dummy load.  The cutouts/distortion are not present at all on the MON audio that comes out of the codec on the 6700.  It happens regardless if I use the hand mic provided with the radio, or my PR40 through the balanced input.

4) If I reduce the number of active panadapters and slices to 7, the problem is very minimized.  If I go to 6 or less, I don't seem to observe it at all. It is very noticeable with 8 panadapters and slices.

My radio is connected to my computer via gigabit Ethernet, through a Netgear 8-port switch.  I observe this issue running a dual 6-core, 3.46GHz X5690 Xeon-based Mac Pro (late 2012 model) with 64GB RAM, both in a native bootcamp session running Windows natively, or if I run Windows 8.1 Pro in a Parallels 9 desktop virtual machine.  Video card in the Mac Pro is a EVGA NVIDIA GTX680 with 2GB RAM.

Keith - AE5XN 

Mack

I just replicated your test procedure using SmartSDR on a W7 W8 computer running the OS natively. There were no transmit audio drop outs for me. This is just a data point to let you know that everyone is not experiencing this issue. 73, Mack W4AX Alpha Tester

Steve-N5AC

Drawing 8 panadapters is still a sizable load on some computers.  To avoid excess latency, the buffer in the radio for transmit audio is only 27ms.  If the PC cannot transmit packets at least this often, the radio will have no data to send and so blank data (no power) will be transmitted.   Some things that might improve the situation:

1. Examine your graphics card and if it is low end or "on the motherboard" a relatively inexpensive graphics card may help.  These are typically about $40.
2. You may have a software-only solution by elevating the priority of the DAX process and your digital mode program over SmartSDR, but I've not tried this
3. If you are full screen, try reducing to just below full screen.  For some reason we have observed that things are a lot harder on Windows at full-screen than just-below full screen.  I suspect there is some kind of optimization that triggers for gaming at full screen and it works at our disadvantage
4. Reduce the draw rate by slowing the FPS on the panadapters to something below the default 25.  The SmartSDR client only draws when it actually receives packets.  If 6 panadapters at 25fps works great, 8 at 18 might work well also

Just as an FYI, buffer size for transmit in the radio is there to help with jitter -- this is the periodic bunching of packets for transmission out of the PC -- but it will not help with the PC falling behind because of a load on the PC that is too large.

Sergey R5AU

Hi Keith, Mack, I wonna try give more information regarding usage of the SSDR on MAC(I am using iMac 27 2010), my experiment was more easy to reproduce: two Pan - on one usual Dax channels with activated playback on second only DAX IQ with 192khz bandwith. Important what this issue related to the size of the SSDR window, in case SSDR larger then( in my case) 1/4 of the screen I hear distortion( audio interaptions ) into the DAX channel, BUT, with SSDR window smaller then 1/4 of the screen size or SSDR window shifted to the an second display - I am really surprised: no distortions or interruption with any number of the active Dax channel which can be activated simultaneously. At first time I think this is SSDR issue, I did many manipulation with installation / deinstallation / factory reset etc, but on fact - MAC HW issue. Paul RN3A tested it also on own iMAC with latest HW - no problem with DAX. Some more abt my setup: iMAC27 16gb ram wth SSD Radeon 5750 with 2Gb Bootcamp + Win7 64 On SSDR AVG=65, FPS=20

Keith - AE5XN

Well, I tried a couple of things:

1) Took out the Netgear GS108NA 8-port gigabit switch and hooked the 6700 directly to one of the Mac Pro's gigabit ethernet ports, thinking it might be a network latency issue induced by the switch.  I still experienced distortion with 7&8 panadapters, so I can rule out that as the culprit.

2) Tried Sergey's suggestion of reducing the size of the SSDR window to less than 1/4 of the screen, and still had the distortion with 8 panadapters.

3) Doing a factory defaults reset on the 6700 via the "OK" and power button.  Still the same result.

Since Mack isn't seeing the issue on his setup, I'm thinking this might be a unique issue with a dual Xeon processor rig, or at least with the older Mac Pro like mine (late 2012).  It happens with both in a native Windows 8.1 Pro (bootcamp) session and in a Windows 8.1 Pro Parallels Desktop 9 virtual machine.  This is the older Westmere Xeon processor with PCIe 2.0 and an NVIDIA GTX680 video card. 

My wife's 3-month old Core i7 (Haswell) iMac is in the shop for a failing IPS LCD display, I'll have to give it a try on that when I get it back from Apple, supposedly towards the end of the coming week.

Keith - AE5XN

Dudley-WA5QPZ

Keith,

Just as a hint,  check your video driver with NVidia.  There has been some graphics issues with some of the NVidia drivers.  

Sergey R5AU

Hi Dydley, you know HW in MAC are very specifically tuned, yesterday I look into ability of installing Catalyst drivers for Radeon GPU on my mac in Bootcamp mode, unfortunately Catalyst reported- HW incompatible on signature side. Means MAC user have no chance try to other way around for new drivers setup.

Tim - W4TME

You may need to allocate more CPU and RAM to the VM that is running SmartSDR.

Keith - AE5XN

Looks like I just solved my problem....

First law of troubleshooting - start with the bare minimum configuration and work your way up.  I still had my SignaLink USB hooked up to the ACC connector and to the USB port on my Mac Pro.  Once I disconnected the SignaLink, the problem went away!

I don't think I was getting any RF into the SignaLink (had MIX 31 ferrites on everything, and I heard distortion even with only 1W output), but maybe the USB drivers for the SignaLink audio codec causing some interrupt servicing (likely, since the problem disappeared with 6 panadapters or less)?  Who knows?  It works great now, and that's all that matters.  I can have the full 8 panadapters and 8 slices active at once, and have undistorted audio now - even on my Parallels 9 virtual machine, without running Win 8.1 Pro from Bootcamp.

Now that DAX is working so well, there's no need for the SignaLink anymore anyway :-))

Thanks to all that gave me suggestions and ideas.  Please feel free to close this problem report as solved.

BTW, for those interested in configuring Parallels 9 Desktop for good performance with SSDR, I've found the following to work well, provided you have the physical memory and # of processor cores to do it:





Keith - AE5XN