Calibrate Local Oscillator in my 6400M

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Staying at home like everyone else I decided to Cal the local oscillator as per the user manual pg 130. It does not say but I will assume that this is done in the AM mode as WWV transmit AM.
I set the Cal frequency at 15 mhz as it gave me a signal of S8&9. The Offset came back as -953.
Is that -953 hz in parts per billion? Manual does not say.
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Andy W3LI

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Posted 2 months ago

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HCampbell WB4IVF

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Official Response
Yes, its ppb, and from what I recall if you're not getting an error msg it's within specs.
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Andy W3LI

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OK, Thanks for the confirmation as the manual does not mention such.
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Robert Lonn

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I did check WWV this morning and it seems to be on frequency, if not I usually call them and tell them to adjust C-1 on their Master Oscillator! When I get exactly 10.00000000000 MHz, they stop adjusting and we are good to go!!!! LOL  :-)   Happy Sunday!!




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Andy W3LI

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Sure U do.....April Fools
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Al K0VM, Elmer

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-953 ppb is -953 hz at 1 Ghz  or  -9.53 hz at 10 Mhz

AL, K0VM
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KC2QMA_John

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What are typical ppb offset numbers people see with 6400/6600?
mine is -1105.
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Andy W3LI

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Hi John, long time no hear.
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Al K0VM, Elmer

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John,
  My 6600 is -1341 ppb this morning..  the spec for the 6400/6600,  as I read it, is for stability 0.5 ppm 0-50C, accuracy and long-term drift are not specified.
AL, K0VM
(Edited)
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KD0RC

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Mine was a little over 1200. I have since connected a GPSDO and it came in at zero when calibrating with WWV at 20 MHz. I have recalibrated a couple of times to see if this is a fluke, and it has stayed at zero.
73,
Len, KD0RC
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Dwayne - NA6US

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I use an external GPSDO. 
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KC2QMA_John

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OK so around 950 to 1500 is normal for the stock internal local OSC?
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Dwayne - NA6US

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-1347 with the internal TCXO and -7 with the external GPSDO on 10Mhz.
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KC2QMA_John

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I think as i get more into digital modes I will look into a GPSDO.
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Al K0VM, Elmer

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As long as it stays in the range that the software cal is able to correct, it should be fine..  Not sure what that range  is though.
AL, K0VM
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Brian Denley KB1VBF

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Mine is zero (No lie!) with an external GPS.
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KC2QMA_John

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WOW Brian, what GPSDO are you using?
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Brian Denley KB1VBF

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BG7TBL one on EBay.  About $150.  I did have to buy the cable to attach to the Flex 10 MHz input conn.  After the setup and the GPSDO and my Flex said they were both locked, I basically pushed the cal button and it came back at 0 at 10 MHz.  Kinda surprised me.
(Edited)
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Dwayne - NA6US

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Mine is 4 on 10Mhz this minute but the Flex will return 0 if it does not find a signal to sync to.
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Brian Denley KB1VBF

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Since the Flex said it was locked on external, can I assume it found the signal?
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Dwayne - NA6US

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No - Note how the radio will switch frequency to calibrate. 10MHz should be good!
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Brian Denley KB1VBF

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No? You don’t think locked means it sees the 10 MHz external GPSDO?
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Dwayne - NA6US

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No means Yes it is locked on GPSDO, but calibration requires you enter 10 (Mhz) and click Start next to the Call Frequency. The radio will then test calibration against a 10 Mhz reference signal. It will then adjust offset in ppb. Click start and let us know what it says. Mine this minute is bouncing between -3 and +4. Essentially noise, but not 0. A cold GPSDO will have a much higher value but better than the internal TXDO.

It would be surprising it always comes back 0 but as a warning, if it does not find a signal (wrong antenna etc) it will come back 0.

(Edited)
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Brian Denley KB1VBF

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Dwayne:
OK yes that's what I did (press start) and it came back with zero.  I'm sure if I do it again i'll get 10 or 7 or -15.  But I did like seeing that zero!  hehe
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Brian Denley KB1VBF

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Dwayne - NA6US

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That’s awesome!
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Geoff - AB6BT

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This is all very interesting. I have a question. What are the practical differences when using a DSPDO? If the radio is capable of of generating an offset to a known frequency standard, WWV for  example, What is the advantage of using a GPSDO?
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Dwayne - NA6US

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GPSDO has a high degree of stability and accuracy over and above the standard TXDO. IMO, really only matters at UHF and beyond.
(Edited)
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Brian Denley KB1VBF

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Not that much Geoff.  I'm not sure you really care whether your contact is 5 Hz off or .00005 Hz off.  I like mine for the frequency calibration and also the time keeping which is exact.
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Dwayne - NA6US

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There is a frequency test contest conducted several times a year. I hope to compete this year.
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George Molnar, KF2T, Elmer

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 GPS is helpful for transverter operation. For HF/6, the stock configuration is absolutely fine. 
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Geoff - AB6BT

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Thanks for all the comments. I see there are a number of uses depending on your activities and applications. 

I appreciate the feedback.