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GNSS vs GPSDO option on 8600

PhilM
PhilM Member ✭✭
edited July 11 in FLEX-8000 Signature Series

From what I have read, the GNSS provided with my FLEX8600 is only for keeping the current date and time (NTP) internal to the radio, it appears to have nothing to do with keeping the frequency that the radio is tuned to stable, not drifting etc, its still using the TCXO for that.

Is that correct or does it have any application with keeping the radio portion of the 8600 stable on frequency for receive and transmit?

Phil

NC3S

Best Answers

  • Trucker
    Trucker Member ✭✭✭✭
    edited July 11 Answer ✓

    The GNSS receiver not only provides time it also is used to keep the frequency stable. If you have it enabled in your 8600 properly, there should be a screen showing the number of satellites it is locked on to. Plus, how much the actual frequency is being corrected in Part Per Billion. It is much more accurate than the TXCO in the radio. Getting a GPSDO can increase the frequency accuracy even better. But, is much more expensive unless you need that kind of accuracy.

    James

    WD5GWY

  • PhilM
    PhilM Member ✭✭
    Answer ✓

    That is good news, to me. The comments I read implied it was to adjust the NTP computer oscillator to properly set it for date and time to be used across various applications and have the same time stamp. For correlation purposes.

    Thanks

    Phil, NC3S

Answers

  • N5NHJ
    N5NHJ Member ✭✭✭

    The 8600 can indeed work as a NTP server for your network, but that is not the main scope of the internal GNSS.

  • PhilM
    PhilM Member ✭✭

    As an interesting observation, I tuned in a CW station before the GNSS said Locked and I could hear the pitch of the other station change as GNSS was adjusting my oscillator.

    73's

    Phil, NC3S

  • JohnEin
    JohnEin Member ✭✭

    Max (N5NHJ) - how, exactly would one go about using GNSS built into the 8600 to keep the clock on a computer accurate? This would be of particular interest to FT8 / FT4 users.

    John NA0A

  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin
    edited July 14

    The GNSS will give you +/- 0.5Hz at 50Mhz. The GNSS constantly updates the TCXO from the moment it is turned on.

    Phil, I doubt that is what you heard until it was the exact moment the GNSS actually locked in and it moved the TCXO.

    John, If you run something like NetTime on your PC, you want to point to the IP address of the radio as one of the Time servers. You will need to keep your 8000 power on (but in at least standby) 100% of the time. NetTime will then resync the clock on your PC.

    BTW, for FT8, you have a +/- 2.5 second window for FT8 and +/- 1.0 second for FT4. You don't have to be that exact.

    https://www.timesynctool.com/
  • Geoff AB6BT
    Geoff AB6BT Member ✭✭✭
    edited July 14

    Mike…

    I just checked the GNSS (GPS Tab) on my 8600. The freq Error is -180 ppb, 32 Sats Visible, 15 Tracked…

    So, at 50 MHz the error is 9 Hz.

    Yours is much better than mine. Is something wrong?

  • N5NHJ
    N5NHJ Member ✭✭✭

    As Mike says, an external NTP client can be used to sync your PC clock.

    Another option is changing the settings of the Windows, Mac IOS, Linux native NTP client to point to the Flex.

    For Windows:

  • N5NHJ
    N5NHJ Member ✭✭✭
  • N5NHJ
    N5NHJ Member ✭✭✭

  • N5NHJ
    N5NHJ Member ✭✭✭

    For Windows just google "windows change time server" and you'll get step-by-step instructions.

    (Sorry for the extra messages, looks like the edit/delete message feature didn't work for me)

    73, Max

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    I just checked the GNSS (GPS Tab) on my 8600. The freq Error is -180 ppb, 32 Sats Visible, 15 Tracked…

    So, at 50 MHz the error is 9 Hz.

    Hi Geoff, You were off by 9 Hz before the GNSS corrected it. Now you are +/- .5 Hz on 6 meters.

  • Geoff AB6BT
    Geoff AB6BT Member ✭✭✭
    edited July 15

    Hi Len, How do I know that is the error after GNSS?

    Thanks.

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi Geoff, +/- .5 Hz is the spec for the GNSS in the Flex. I think that the GPSDO is better than that (for big $$$), but I don't know the specs for it.

    +/- a half Hz at 50 MHz is crazy good! Back in the day, if I could get my novice HR-10 B calibrated to a KHz or so, I was happy!

  • Geoff AB6BT
    Geoff AB6BT Member ✭✭✭
    edited July 15

    OK,Thanks. I suppose that's in the user guide.

    HA! My first receiver was an S38-E. I think the 15 Meter band was about 1/2" bandspread on the dial. But somehow I was able to make CW contacts. Sometimes the station I was working was actually in the passband without retuning.

  • Geoff AB6BT
    Geoff AB6BT Member ✭✭✭

    OK, where is the GNSS frequency accuracy spec published?

    Sorry, I can't seem to find it…

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    https://www.flexradio.com/documentation/flex-8600-8600m-spec-sheet/

    .001 ppm (GNSS) is the spec. That translates to .5 Hz at 50 MHz (i.e. worst case).

  • Geoff AB6BT
    Geoff AB6BT Member ✭✭✭
    edited July 15

    Thanks Len, I looked in the hardware and software guides but not at the radio spec sheet.

    Thanks for pointing me in the right direction.

    Using an on-line calculator I get this:

    image.png
  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Oh, right, .05 Hz!

  • Geoff AB6BT
    Geoff AB6BT Member ✭✭✭

    I guess I can live with that!

  • PhilM
    PhilM Member ✭✭

    I asked AI about it, and this is what it came up with. Sounds reasonable to me…

    Frequency Stability with GNSS on the FLEX-8600

    The FLEX-8600’s built-in GNSS disciplining holds its internal TCXO to within ±0.5 Hz at 50 MHz.

    What This Means Across HF Bands

    Because the disciplining error scales with frequency, you can expect roughly:

    RF Band

    Frequency (MHz)

    Maximum GNSS-Disciplined Error (Hz)

    40 m

    7

    ±0.07

    20 m

    14

    ±0.14

    10 m

    28

    ±0.28

    6 m

    50

    ±0.5

    Phil, NC3S

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