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SDR Latency Warning During Installation Process.

All:

It might be a good idea to mention SDR latency in a message that appears during the VarAC installation process. I've run into several hams using Flex and other SDR transceivers who were not aware that the issues they were experiencing with VarAC were due to latency. I've noticed that the TX/RX collisions that occur due to latency are usually detectable by the receiving station working the ham with an SDR and I usually send an email to let them know what the potential issue might be.

The other alternative would be to have Jose modify the VARA modem.

Tony -K2MO

8 comments

8 Comments

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NC3Z Gary

Jan 15

I use 600Hz filter on my 6500, only ever had issues when connecting to a SunSDR, but my 7300 also had issues with the Sun. But the new VARA HF and VarAC has made this an issue of the past.

N8SDR

Jan 14

Tony and I just a QSO and all seemed to go well, need to test these changes another day or two then will post the complete changes in Win11 I have done which seems to have helped, these should also apply to windows 10 as well. Thanks, Tony, for the test and qso

N8SDR

Jan 13

My rate has jumped some 80% + percent since we worked with those changes Gary. One Thing I have found out is Windows 11 has some issues with Audio Latency! I am currently using 11 and can verify that! I have made some changes with some registry settings and a few other tweaks which has helped even more. Had a nice chat earlier today with Russ in Florida for about 10 minutes or so and things went well here. I'm using A SunSDR2DX , with Winturd11. Key thing would be to ask the other user if that have upgraded to 4.5.5? if there still on 4.5.0 it will certainly have a bit more latency for SDR rigs. One thing I also suggest if your using VAC (virtual Audio Cable) with windows 11 try and use the WASAPI drivers and not the MME or other variants- here is a good article regarding this audio latency and win10 and win11 Low Latency Audio - Windows drivers | Microsoft Docs

73guddx

Jan 13

Replying to

Rich:

Glad to hear things are working for you. You mentioned your rate jumped 80% so I'm assuming you were still having latency issues with VARA 4.5.5? I guess all is well now since you've tweaked the driver issues and VAC?

Tony -K2MO

N8SDR

Jan 13

Replying to

@73guddx 4.5.5 certainly has helped a lot. Some of this I think is the way the EESDR SUNSDR rigs work I'm working with Expert Electronics to see if a way to speed RX/TX cycle time. Again windows 11 is certainly another thorn with audio latency. and I suspect some contacts with other SDR users still using the old version of Var HF 4.5.0. Gary with his 6500 and I seem to contact on first try most of the time now, that was a big jump. as well as me connecting with Larry w1izz who I could not at all before. One other thing I'll note is this poling time in OmniRig, if that is set low it can interfere with cycle, there isn't a need for the radio to be polled every 100ms, 550 or more can help because you're not tying resources in obtaining status of the rig. I have seen quite a few posts showing that at 100ms

NC3Z Gary

Jan 13

The changes from VARA HF 4.5.0 to 4.5.5 were to address latency issues with SDR's. You do not see versions 4.5.1 to 4.5.4 in Jose's change log as several of us were beta testing the timing issues with the help of Irad. There were also some beta VarAC before 3.0.2 to help with this.

Because of this we now have several Flex 6xxx, Flex 5000 and SunSDR's now able to do SDR to SDR connects with some great results.

I am having no issues at all with my Flex 6500, and I have made a few QSO's.

Who is still having an issue?

73guddx

Jan 13

Replying to

Gary:

Apparently, the issue still exists and my guess is that it could be an SDR setting that's causing the problem. I tried to work AF3K today without success and it was clear that he was having latency issues with his SDR. I emailed him this afternoon and will advise when I receive a reply. I was running my IC-7300 at the time.

I've worked with Jose in the past to fix latency issues I had with my Flex 6600M which showed up while running Winlink. His tweaks worked for the most part, but there are times when I experience a collision or two. I'll have to try my Flex with VarAC and see how things go.

Tony -K2MO

73guddx

Jan 15

Replying to

Gary:

Just received word from AF3K. He was using his Flex (6700) at the time of our QSO which explains the latency issue. He was also using the latest version of VARA and VarAC. If other Flex users aren't having latency issues with the current versions then it must be the settings within the rig.

I know that sharp filter settings add latency and Flex does recommend using wide filter settings when working ARQ modes in order to reduce latency during the demodulation processes.

According to Flex, a filter setting of 500 Hz or less adds 85ms while a filter greater than 2K only adds 11ms. My guess is that the overall system latency is higher and that could be cutting it close when you consider the fast TX/RX timing of the VARA modem.

It could also be something simple like having the delay (break-in) slider set to high although I'm not sure if it functions in USB-D / LSB-D modes.

Tony -K2MO