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6700 Internal Signal at 10 MHz?

K1FR
K1FR Member ✭✭
edited June 2020 in FLEX-6000 Signature Series
Is it normal to see about a -95 dbm signal right at 10 MHz? I am setting up for a frequency measuring project for HamSCI which requires 72 hours of monitoring WWV at 10 MHz. In looking at my test data I noticed this signal always present. Regardless of antenna being connected or not or grounded. I am just guessing it is the 10 MHz reference signal output from the GPSDO in the 6700. Does that make any sense?

Thanks for any info. This has me thinking my data for the HamSCI project may not be very useful.

73, Tom
K1FR

Answers

  • Martin AA6E
    Martin AA6E Member ✭✭✭
    edited June 2020
    I see the same on my 6500 + GPSDO.  Try 5 or 15 MHz WWV or other standard frequency signals?  Maybe try removing GPSDO to verify that that is the issue. Disabling by software does not help.

    If it's constant amplitude and phase, you could theoretically null out the birdie by feeding back a part of the 10 MHz oscillator output.

    73 GL  Martin AA6E
  • K1FR
    K1FR Member ✭✭
    edited June 2020
    Thanks, Martin. Appreciate the reply. Good to know it is not just me.

    We need to use 10 MHz WWV because the experiment is also using a Chinese and other 10 MHz time/frequency beacons and needs to use data from all. Checking with the experiment lead indicates the purity of the Flex GPSDO should still allow the 6700 to measure the ionosphere induced doppler differences well enough for their purposes. So, guess it is a non problem. Will see how it turns out.

    73, Tom K1FR

  • Andrew VK5CV
    Andrew VK5CV Member ✭✭
    edited June 2020
    Thank you Tom,
    I had seen that project and do get some GPSDO leakage and WWVH as well.
    So was wondering along the same lines.
    "minds on the same wave length"
    Andrew VK5CV

  • K1FR
    K1FR Member ✭✭
    edited June 2020
    Thanks, Andrew! Good luck during the experiment. I am guessing your data will be far more useful than ours here in NA since you can probably hear both WWVH and the China signal as well.

    Will look forward to seeing their results.

    73, Tom 
    K1FR

  • Dan-N7HQ
    Dan-N7HQ FlexRadio Employee, Community Manager admin
    edited June 2020
    Depending on the RX (unterminated) input, I see a signal between -101dBm and -109dBm when tuned 10MHz on my 6700 +GPSDO.  I also distribute the 10MHz output from my 6700 as a reference for some test gear.

    On all models (with or without a GPSDO), I routinely see a small signal there and attribute it to leakage from the internal 10MHz clock.  

    73,
    Dan, N7HQ
  • K1FR
    K1FR Member ✭✭
    edited June 2020
    Thanks, Dan!
  • KD0RC
    KD0RC Member, Super Elmer Moderator
    edited June 2020
    I have the Leo Bodnar GPSDO, and with it on, I have a -108 dBm signal at 10 MHz with no antenna connected (Flex 6400).  If I power down the GPSDO, I have an -115 dBm signal there.  Not many spurs with this rig!
    73,
    Len, KD0RC
  • K1FR
    K1FR Member ✭✭
    edited June 2020
    Len: Thanks. Amen - the Flex is one heck of a radio and super clean. But, it sure makes it clear how noisy my QTH is!  :)

    73, Tom
    K1FR

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