Signal receive tming?

W7VD Bob · December 2020

I just noticed that my 6700 produces audio and amplitude signal on waterfall about 1/2 second behind the analog receiver here. Is this normal for an SDR receiver??

KD0RC · December 2020

Hi Bob, latency is normal for SDR radios. The long latency you are experiencing is more likely in your network. Are you connected to the Flex with WiFi or is your computer directly wired to your network? Are you connected remotely using SmartLink?

73,

Len, KD0RC

Ted VE3TRQ · December 2020

Windows audio also generates latency, as much as a couple hundred milliseconds.

KD0RC · December 2020

Good point Ted! Bob, are you using speakers or headphones plugged into the Flex, or audio from the PC? If from the PC, that could account for most of it.

Len

John KB4DU · December 2020

Latency is also affected by filter settings. Perhaps start by checking the filter settings for low latency settings.

AWe · December 2020

I can tell you non of the other SDR´s on the market have noticeable delays with Windows (Hermes, SunSDR, Zeus).

Flexradio with MAC-Software does have minimal delay.

Flexradio with Windows (also Maestro) has 0.5 to 1s delay, thats way too much and NOT normal!

The support knows the problem but has no idea how to implement Windows low latency audio path since 3 years.

ka9ees · December 2020

I haven't noticed any delay with my iPad. Nor do I notice any with Windows as long as the rig and the computer are plugged into the same network switch.

Ed KA9EES

ka9ees · December 2020

@DL4RCE 6400M

DL4RCE · December 2020

No lag only if I plug headphones/mic directly into my 6600 Flex. @ka9ees what model do you have?

73 de Volker

jwhths · September 2021

The most likely reason for noticing audio lag is using the PC Audio button. In Windows 10:

(1) Turn off PC Audio
(2) Navigate to Settings / Sound / Choose your input device.
(3) Pull down to DAX Audio RX 1, then click through to Device properties. (on my computer, it still displays 'Microphone', but ignore this).
(4) Click through to Additional device properties.
(5) There are four tabs – general / listen / levels / advanced. Go to the Listen tab and check the 'Listen to this device' box.

With the new setting, I can tune to WWV and listen to the one second marker clicks. When I turn on PC Audio again, I hear a double click – the low lag DAX Audio followed by the long lag PC Audio.

I am using a pair of Asus wireless routers, one as a WAP, the other as a media bridge connected to my 6600.

Mike-VA3MW · September 2021

I explain it in this thread

https://community.flexradio.com/discussion/8023291/rx-audio-latency

W7NGA · September 2021

The original posting referenced the delay he hears between the Flex and an analog receiver (non-SDR without DSP). The Flex processing takes time. It is much like talking on the phone versus telling another person what you want to say and then they talk. The person on the other end will hear a delay. They won't know there is a delay if they don't hear the original talker. The Flex latency can be mitigated somewhat by changing filtering parameters but it certainly isn't an issue for me. Contesters seem bothered however, that another operator using an old Heathkit or Hallicrafters radio hears a CQ DX a tenth of a second sooner than they do and therefore hold an advantage. I mean, they do .. but there is also latency going the other way. You talk or press the CW key and it takes a while before your glorious RF emanates to be pushed down your low-velocity factor coax and into the ether.

Open-wire feedline all they way baby ...

W7NGA

Mark_WS7M · September 2021

I don't have any working non SDR radios to compare at the moment. I do agree with all said above.

If I run my Icom 7610 and Flex (using direct audio to headphones) next to each other the difference is very small. I have not tried to measure the difference and it can barely be detected.

Turn on PC audio and yes the flex is now like 1/2 second behind.

I am not a real serious contester. I do some but I'm not ever trying for that top score, I mainly run to continue my CW proficiency.

Years ago on the forums there was a ham that did a BUNCH of measuring of both RX and TX latency and did a bunch of complaining about it and I think sold his flex for something else.

Maybe at his level it truly made a difference, but I will say that with a flex and the ability to zoom that pan way in I am extremely successful at DX because I can track the stations he is answering and position my TX right where I think he will listen next.

I don't have a killer antenna. Just a loop at like 45 feet and a PGXL but I usually get in within a few moments with the DX if he can hear at all.

I get that this ability is probably not a contest feature but in a busy contest I do find the ability to fiddle with the filters and TNF to be a life saver when some idiot decides to setup CQ just 150hz away. I can usually null him out pretty well and still hear the people I'm trying to work.

KD0RC · September 2021

To add to what Mark said, I am also not a real contester, but when I do jump in, I find that a slight hesitation before punching the PTT usually gets better results.

I think it was Mike, VA3MW who said that it is not the first signal heard, it is the first signal correctly copied that gets the reply.

I can sometimes beat the big guns by timing my transmission to come in after the unintelligible din of the louder signals all transmitting at once.

That being said, the really big signals often do get worked first, but I think that is due to being louder than everyone else, not because of low latency.

Signal receive tming?

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