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Latency Issues with SCS Modem

Kg5dwx Member ✭✭
edited June 2020 in SmartSDR for Windows
If I quit using the wireless router and direct connected the Flex 6500 to my PC's NIC, would this reduce latency issues?


  • N3NER
    N3NER Member
    edited March 2018
    Yes, direct connection to your network will in most cases give you much better performance.
  • Kg5dwx
    Kg5dwx Member ✭✭
    edited February 2017
    I ment to say, a cable direct from the 6500 to the pc's NIC.
  • N3NER
    N3NER Member
    edited March 2018
    Oh, I don't think that would change anything that much but I'm sure someone will chime in.  But I think a network of some kind is needed.
  • Steve N4LQ
    Steve N4LQ Member ✭✭
    edited August 2019
    Yes. It's much better when directly connected to the NIC in the PC. I added another NIC card just for that. A wired connection to the LAN works well. WiFi is spotty unless you have a really good signal but nothing beats a direct connection.
  • Peter K1PGV
    Peter K1PGV Member ✭✭
    edited June 2020
    From a networking perspective connecting to your radio directly should be identical to connecting via a switch. The network stack doesn't know that you're directly connected, to the best of my knowledge. Therefore, there should be no advantage or disadvantage to connecting directly (or via a switch). I would expect the protocol exchanges involved to be identical.
  • Tim - W4TME
    Tim - W4TME Administrator, FlexRadio Employee admin
    edited December 2016
    The only advantage a switch has is, depending on the architecture, additional packet buffering which may improve throughput performance.
  • Ed.G
    Ed.G FlexRadio Employee ✭✭
    edited February 2017
    I believe that in the case of the SCS modems they are usually wired through the ACC port on the 6000 series. In this case the way that PC is connected to the radio will have no real impact on the latency the modem sees. 

    Note that for low latency modes (PACTOR etc) you need to be in DIGU or DIGL with a filter skirt larger than 3kHz so that the radio uses low latency filters and bypasses the PROC and EQ.
  • Ed baker
    Ed baker Member ✭✭
    edited September 2016
    Since I have a scs modem P3 , P4 protocol I can tell you that I was not able to use my 6500 with this modem and running any forward error correcting mode ..

    You are correct the latency does get in the way .

    You need 8 MS or less .

    Before you quit :
    Try the robust mode on the scs program . It may be good enough for your use . Ed G is on the right track . However without being able to reduce the sample size less than the default for flex little relief is available. If you ever wondered why some of the legacy radios used in the marine industry work so well with the SGC modem it is because of the latency factor is way down . the filters are as wide as a barn door and they have fast T/R recovery . All a benefit to FEC but not for us .
  • Clay N9IO
    Clay N9IO Member ✭✭
    edited December 2016
    I have a PCIe Gb NIC and a slot open in the PC.
    How does it wire, Flex to one NIC, the other NIC to the LAN router?
    I had thought about this before, would it really be worth the trouble?
    Keep in mind that I am not on topic as I do not run the modem in this thread,
    I am just taking about how it works to improve the SSDR / Flex relationship.
    Clay N9IO
  • Steve N4LQ
    Steve N4LQ Member ✭✭
    edited September 2015
    Exactly Clay. 

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