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Author Topic: Signal delay with SDR  (Read 3414 times)
NO9E
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Posts: 616




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« on: December 14, 2016, 04:31:40 PM »

I am looking into a remote site with SDR and antenna to take care of RFI. But the SDRs I am trying locally have delays: perhaps 1/4 second for SDR-IQ and almost 1/2 second for SDRplay. I tried both with different software. The delays are too long for running.

Apparently a good remote setup has a delay < 0.1 s. So why the delays with SDR-IQ and SDRplay locally?
Are they due to USB or specific settings in SDR software?

Ignacy, NO9E

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K9AQ
Member

Posts: 74




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« Reply #1 on: December 16, 2016, 06:41:22 AM »

Ignacy,

I have observed a similar latency delay in my SDR Play, which I use as a panadapter for my Elecraft K3.  I just started experimenting with using SDR Play and HDSDR as a sub receiver for the K3.  I was hoping that I could do that and avoid having to purchase the Elecraft sub receiver.  I have it working remotely using RemAud for the audio transport.  My "normal" latency is a little less than .1 second, but I have not actually measured it.  When I try to also run the "sub receiver" audio, the extra audio channel  overloads my DSL Internet connection, slowly down my rig control.  I don't have another option for higher speed Internet, so I put the SDR Play sub receiver on the shelf until sometime in the future when hopefully I can get faster Internet.

73,

Don
K9AQ
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NO9E
Member

Posts: 616




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« Reply #2 on: December 16, 2016, 07:44:03 AM »

Thank you for the info. I have also found two extra sets of information:
http://www.lz1aq.signacor.com/docs/std/Measurements_of_Signal_Time_Delays_in_Several_SDR.htm
   and
http://www.sm5bsz.com/lir/rxdel/3-26in/rxin.htm

It seems that USB adds little and most of delays are due to large buffers.

There are benefits to 2nd rx in K3 and P3 despite costs. Both are working in a second after turning on, and without artifacts. 

Ignacy, NO9E
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ONAIR
Member

Posts: 3158




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« Reply #3 on: December 24, 2016, 10:56:12 PM »

I am looking into a remote site with SDR and antenna to take care of RFI. But the SDRs I am trying locally have delays: perhaps 1/4 second for SDR-IQ and almost 1/2 second for SDRplay. I tried both with different software. The delays are too long for running.

Apparently a good remote setup has a delay < 0.1 s. So why the delays with SDR-IQ and SDRplay locally?
Are they due to USB or specific settings in SDR software?

Ignacy, NO9E


   I've noticed a slight delay when hearing an incoming signal via online SDRs ( www.WebSDR.org ) compared to my regular receiver.  It's not enough of a delay to prevent a QSO however.  Many times I can hear the other station better via the online SDR than I can at the base, because of high local noise levels. 
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K9AQ
Member

Posts: 74




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« Reply #4 on: January 13, 2017, 05:36:11 PM »

Does anyone have any recommendations on how to reduce the amount of audio latency?  My configuration is an Elecraft K3 with the IF output going in to SDRPlay, and running HDSDR software.  I am running Windows 10, 64 bit, on a quad core PC. 

This works great as a visual panadapter but there is a very noticeable amount of audio latency when trying to use this combination as a sub receiver.

Is the primary cause of the audio delay the HDSDR software or the SDR Play hardware?

Thanks for your help.

73,

Don
K9AQ
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