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On a Flex 6500 what is the input impedance of the 10 MHz IN (is it internally 50 ohms to gnd)

allanmryan Member
I'm trying to trouble shoot an external 10 MHz GPS disciplined oscillator. Measuring the unterminated RCA male I get 2.2 V P-P square(ish) wave. If there is an internal 50 ohms to ground, connecting the cable to the 6500 will cut that voltage in half and be marginal.
Al Ryan

Best Answer

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

    The 10Mhz input will accept a square or sine wave. The impedance is somewhere between 50 and 70 ohms if I remember correctly.

    You can safely plug it in a test it. I have tried a few different 10Mhz references and they all seem to work just fine.


  • N5DUP
    N5DUP Member ✭✭

    Wait a minute, I thought the 10 MHz jack on my 6400 was a 10 MHz reference OUTPUT if you have the Flex GPSDO, not an INPUT. Am I wrong?


  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi Paul, there is a 10 MHz input labelled 10 MHz In. If you have a Flex internal GPSDO installed, then you will also have a 10 MHz Out jack. If you don't have the Flex GPSDO, then the 10 MHz Out port has a metal plug in it.

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