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Spike in Latency

NG0Z Member ✭✭
edited September 2022 in Networking

My latency has been consistent at around 60ms for some time and then all of a sudden went to 82-100ms including some disconnects where SmartSDR loses connection.

I called Xfinity to report the latency as reported by SmartSDR. They performed some minor fixes to the connectors between me and the neighborhood hub but otherwise determined their network is exceeding specs. Download and upload speeds are north of 600mbps but of course, we all know it's not the speed - it's the latency that matters to remote-operated Flex stations.

The internet connection at the transmitter site is high-speed cable as well with a new switch and router.

All internet connectivity on both ends is direct-connect. No WiFI.

Bufferbloat gives me an A on the transmitter site's network and an A on the remote site's network where I have a router recommended by Bufferbloat (eero Pro 6) and turned on the Beta option for optimizing for gaming.

Question is, how do I determine what is causing the latency, or on which end is it occurring?

The Flex 6400 is new, with the latest firmware (v3.3.32). Also, I may be seeing some flux in latency when transmitting but not 100% sure of the correlation.

Thank you,




  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin


    What it sounds like is that your CPU or NIC card is the bottle neck. You have elminiated most other things it seems.

    80-100ms doesn't sound too bad, but that shouldn't cause SmartSDR to fail unless there was a total packet loss. Again, there are many players from the network, to the radio and also the PC and the TCP/IP stack in the radio. They all have an impact.

    Running a DPC Monitor might help to show that.

    The Switch could also have network ports that are flapping. Changing out the switch might make a difference. If it was me, I would try a simple 100mb switch and see if the symptoms change.

    Others may have more input.


  • NG0Z
    NG0Z Member ✭✭
    edited September 2022

    There was tremendous packet loss yesterday and the radio was unusable. Latency well above 100ms.

    Today the issue has all but disappeared. We had been running Trace Reports and watching the long path that my ISP was hauling the traffic between the city and the transmit site. The latency appeared to be the thousands of miles the signals were traveling. Perhaps they had an equipment failure was offered by my network engineer friend.

    Today, after a short overnight outage, the path has shortened dramatically and the radio is working well.

    60ms isn't awesome, and certainly not what I'm paying for but at least the radio works seamlessly at that rate.

  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    60ms is a good number. Maybe not for gaming, but it is more than adequate for HF radio operation.

    60ms is about the length of one CW Dit at 25wpm.


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