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Flex-6700 External GPSDO Questions

Ed, K0KC
Ed, K0KC Member ✭✭
edited June 2020 in FLEX-6000 Signature Series
I have recently acquired a Leo Bodnar mini GPSDO unit (set to 10 MHz) to use with my Icom IC-9700 radio. I have also recently ordered a 3 dB splitter to enable me to route the GPSDO signal to both the Icom IC-9700 and my Flex-6700.

  • I was wondering if the Flex internal oscillator will be truly locked to the external GPSDO signal or if it will only check the external signal periodically and make any  necessary frequency adjustments?

  • I also would like to know if the external GPSDO signal will only be effective for ANT 1 or if it will also be effective on ANT 2 and the transverter I/O? I understand that the calibration capability normally used to calibrate versus WWV would have to be invoked.

  • Since I currently use a Down East Microwave 2MLDPA amplifier with the Flex-6700 transverter I/O, will it correct the significant transmit and receive frequency errors that I experience on 2 meters with the Flex-6700?

  • If I purchase a Down East Microwave transverter in the future (driven from the Flex-6700 transverter I/O) will I still experience the transmit and receive frequency errors that I currently am seeing on 2 meters with the Flex-6700? If the answer is "yes", would a reasonable solution be to use a transverter with 10 meters as an IF? Would I be required to only use ANT 1 in this case?
Thanks in advance for your guidance!

Ed, K0KC

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Answers

  • Al K0VM
    Al K0VM Member ✭✭✭
    edited May 2020
    Ed,
      The Flex internal master oscillator will be locked to the external GPSDO. All RX & TX frequency dependent functions are derived from that master reference.  With a GPSDO, running the frequency calibration should return numbers near zero, the difference being propagation doppler shift.  You can set the Flex correction to zero and forget it with a GPSDO.   Unless the external transverters are also synced to a GPSDO, they could have their own frequency errors.

    AL, K0VM
  • Tim - W4TME
    Tim - W4TME Administrator, FlexRadio Employee admin
    edited May 2020
    You asked...

    I was wondering if the Flex internal oscillator will be truly locked to the external GPSDO signal or if it will only check the external signal periodically and make any necessary frequency adjustments?

    The GPSDO acts as the driver XO for the master XO as Al noted.

    I also would like to know if the external GPSDO signal will only be effective for ANT 1 or if it will also be effective on ANT 2 and the transverter I/O? I understand that the calibration capability normally used to calibrate versus WWV would have to be invoked.

    That isn't how the GPSDO works.  It disciplines the master XO.  It is not involved with the RX signal path

    Since I currently use a Down East Microwave 2MLDPA amplifier with the Flex-6700 transverter I/O, will it correct the significant transmit and receive frequency errors that I experience on 2 meters with the Flex-6700?

    Yes.

    If I purchase a Down East Microwave transverter in the future (driven from the Flex-6700 transverter I/O) will I still experience the transmit and receive frequency errors that I currently am seeing on 2 meters with the Flex-6700? If the answer is "yes", would a reasonable solution be to use a transverter with 10 meters as an IF? Would I be required to only use ANT 1 in this case?

    Yes. You use the XVTR port for any external transverters and it will not make a difference what the IF frequency is you are using.  The VXTR bands only work with the XVTR port, so you would have to disconnect or use a switching matrix to disconnect the 2MLPDA.  Using an ANT-x port for a transverse has a significant risk of transmitting a lot more wattage into the transverter and blowing it up whereas this is not the case when using the XVTR port that has a max of +15 dBm output power.
  • Tim - W4TME
    Tim - W4TME Administrator, FlexRadio Employee admin
    edited May 2020
    You asked...

    I was wondering if the Flex internal oscillator will be truly locked to the external GPSDO signal or if it will only check the external signal periodically and make any necessary frequency adjustments?

    The GPSDO acts as the driver XO for the master XO as Al noted.

    I also would like to know if the external GPSDO signal will only be effective for ANT 1 or if it will also be effective on ANT 2 and the transverter I/O? I understand that the calibration capability normally used to calibrate versus WWV would have to be invoked.

    That isn't how the GPSDO works.  It disciplines the master XO.  It is not involved with the RX signal path

    Since I currently use a Down East Microwave 2MLDPA amplifier with the Flex-6700 transverter I/O, will it correct the significant transmit and receive frequency errors that I experience on 2 meters with the Flex-6700?

    Yes.

    If I purchase a Down East Microwave transverter in the future (driven from the Flex-6700 transverter I/O) will I still experience the transmit and receive frequency errors that I currently am seeing on 2 meters with the Flex-6700? If the answer is "yes", would a reasonable solution be to use a transverter with 10 meters as an IF? Would I be required to only use ANT 1 in this case?

    Yes. You use the XVTR port for any external transverters and it will not make a difference what the IF frequency is you are using.  The VXTR bands only work with the XVTR port, so you would have to disconnect or use a switching matrix to disconnect the 2MLPDA.  Using an ANT-x port for a transverse has a significant risk of transmitting a lot more wattage into the transverter and blowing it up whereas this is not the case when using the XVTR port that has a max of +15 dBm output power.
  • Steve Sterling
    Steve Sterling Member ✭✭
    edited May 2020
    Agree with Al-- master oscillator locks on. Never more than 1 or 2 ppb off from 10Mhz WWV, except if my cheap external GPSDO is in cold startup-- about 24 hours for it to get to final stability. Worst it ever gets is 4-5ppb off when the GPSDO is cold.
  • Ed, K0KC
    Ed, K0KC Member ✭✭
    edited May 2020
    Thanks, Al, Tim, and Steve!!!

    My concern is with 2 meters where I now (without a GPSDO) have to set my receive frequency on the 6700 to 925 Hz higher to match a properly calibrated IC-9700 and my transmitted frequency 465 Hz lower (XIT = -465) again to match the IC-9700. I have checked these corrections with my own IC-9700 as well as with an IC-9700 owned by a local ham. Both 9700s use the GPSDO reference input, so I am pretty confident that they are calibrated to 1 Hz or better on both transmit and receive. I have also checked the above receive correction with the Leo Bodnar oscillator set to 144.174 MHz (it can be adjusted up to approximately 800 MHz) feeding the 2 meter antenna input through an attenuator.

    Once I correct the master oscillator on the 6700 with the GPSDO, it seems like either the 2 meter receive or transmitter frequency may be corrected, but not both...please let me know if my thought process is off here.

    I will report back when I receive my 3 dB splitter later in the week and have the time to do some tests.

    Ed, K0KC
  • Al K0VM
    Al K0VM Member ✭✭✭
    edited May 2020
    Ed,
      I don't own a 6700 so can't duplicate your findings.  If presented with your results, the first things I would do is do a factory reset on the radio & run the radio Frequency calibration routine against WWV or CHU.  What correction does the calibration report ?  

    If the 2m results persist after the calibration run, its unlikely that a GPSDO will change anything.  Then it might be time for a help desk ticket. 
     
    AL, K0VM
  • Ed, K0KC
    Ed, K0KC Member ✭✭
    edited May 2020
    Al, thanks for the hint!

    I have run a number of calibration routines against WWV over the years with my 6700 (it was one of the early ones...Signature Edition) but never after a factory reset. The correction after running such a routine is about -3500 ppb as I recall. This seems high, but the HF bands seem ok, but not 2 meters. I will give the factory reset approach a try after saving my profiles and memories (please Ed, don't forget to save them first!).

    There are a number of posts on this Community regarding 2 meter frequency errors and as I recall, people have worked around the problem as I have. I have seen nothing indicating that Flex has addressed this problem, so a help desk ticket would probably not get me anywhere but might be worth a try.

    Ed, K0KC
  • WX7Y
    WX7Y Member ✭✭✭
    edited June 2020
    Watch it close and make sure the GPS stays locked on the 6700, Mine will drop lock after a few days time and I have to reboot the Radio to get it to reconnect to the radio, I have my 10MHz source split like I'm sure your doing between the 6700 and 6600M and the 6600M ALWAYS stays locked but the 6700 drops. 
    It makes no difference if  I Tee the 10MHz source or not it still drops on the 6700 and it's NOT a signal strength issue.
    73's
    Bret

  • Ed, K0KC
    Ed, K0KC Member ✭✭
    edited May 2020
    Thanks, Bret!

    How would I know that my 6700 has lost lock? I normally turn the 6700 off each night, so I might not see the problem arise.

    Ed, K0KC
  • WX7Y
    WX7Y Member ✭✭✭
    edited May 2020
    if you turn the radio off then it would not bother you at all.
    I leave mine on all the time.
    To check it first unplug the 10 MHz source then go to WWV (I use 10 MHz for my location) turn your VFO to 10.000MHz and ZOOM way way in and see where WWV's carrier is at on your Panadapter, it should be within maybe 100Hz+- if the internal oscillator is working right. 
    Turn the Radio off then plug the 10MHz source back in turn the radio on and see where your at on the panadapter should be much closer to the WWV signal on the Panadapter to 10.000MHz WWV carrier it should be with in 10hz or less depending on how accurate your source 10MHz is. 

    Leave the radio on for a few days and check it again and on MY 6700 it is back to the internal oscillator frequency. 

    The F6600M never looses the external source and shows in the radio's setup window. 

    hope this helps
    Bret

  • Ed, K0KC
    Ed, K0KC Member ✭✭
    edited May 2020
    Thanks to everyone for their help!

    It looks like the GPSDO has solved the 2 meter calibration problems on my Flex-6700.

    I received my 3 dB splitter today, connected it to the Leo Bodnar unit and hooked one port to the Flex-6700 and the other to my IC-9700. I ran the calibration routine on the 6700 and it showed that I was -3 ppb off from WWV as compared to -3767 ppb without using the GPSDO input. I then switched to 2 meters and a quick check against my IC-9700 (which is also GPSDO driven) looks like the Flex-6700 2 meter transmit and receive frequencies are right on...no "fudge" needed!

    Ed, K0KC
  • roger na4rr
    roger na4rr Member
    edited May 2020
    Leo Bodnar mini GPSDO  does this come with the cables to hook it up to the 6700? 

    i bought the one flex sells that mounts right in the 6700.  That was nice but they want way too much money for it.  Mine died, of course, just after, they said it was out of warranty.  I keep having to increase my offset.  For 6 meters I'm up to -16000 to get 50.313 to decode.

  • Geoff AB6BT
    Geoff AB6BT Member ✭✭✭
    edited May 2020
    Just curious, why do you have to increase the offset? What happens when you run the calibration routine against WWV?
  • roger na4rr
    roger na4rr Member
    edited May 2020
    Cal routine wont bring it in. Its been awhile since I've run it  I'll give it another try and see how it does.
  • Geoff AB6BT
    Geoff AB6BT Member ✭✭✭
    edited May 2020
    Copy, standing by...
  • Steve Sterling
    Steve Sterling Member ✭✭
    edited May 2020
    Just like it should.
  • Ed, K0KC
    Ed, K0KC Member ✭✭
    edited May 2020
    Steve,

    The Leo Bodnar Electronics mini GPSDO unit that I have uses an SMA female connector for the RF output, a USB-C connector for power (I power mine from a USB port on my computer, cable included with the unit), and a connector for the GPS antenna (antenna and cable comes with the unit). You would have to provide a cable for SMA male to RCA male to connect it to the rear panel of the Flex.

    Ed, K0KC
  • Tim - W4TME
    Tim - W4TME Administrator, FlexRadio Employee admin
    edited May 2020
    There is actually a defect in the 6700 where the 2m frequency is off regardless if you use WWV or CHU to frequency calibrate the radio.  If you use an external driver XO (GPS or Rb), the frequency error is corrected.
  • Ed, K0KC
    Ed, K0KC Member ✭✭
    edited May 2020
    This is what I discovered accidentally...a pleasant surprise!

    Ed, K0KC
  • Ed, K0KC
    Ed, K0KC Member ✭✭
    edited May 2020
    Looks like I was a little too quick in singing the praises of my 10 MHz GPSDO and my Flex-6700. The 6700 seems to lose lock with the GPSDO on a frequent basis. The only way that I have found to bring it back into lock is to close SmartSDR, shut down the 6700 and then restart. I have tried a number of output power levels from the GPSDO without success.

    Ed, K0KC
  • WX7Y
    WX7Y Member ✭✭✭
    edited June 2020
    Yep as I stated in a message on this thread last week with the External GPS so your not alone.
    hope you find a answer, if you do let me know.

  • Ed, K0KC
    Ed, K0KC Member ✭✭
    edited May 2020
    Yep, Bret, you warned me!

    I will experiment a bit more, but I have a feeling this is something that will not be under my control.
  • Larry _ NY8T
    Larry _ NY8T Member ✭✭✭
    edited May 2020
    My 6700 does the same with the Trimble and BG7TBL GPSDO's.
  • KD0RC
    KD0RC Member, Super Elmer Moderator
    edited June 2020
    I have the Leo Bodnar unit, and it seems to always work.  I do shut down my Flex 6400 every night, but leave the GPSDO running.  The Flex always says Locked, so I kind of stopped checking, but when I first got it, I checked several times a day to see if it was really working.  I also discovered that I can change the source to TCXO, and then back to GPSDO without powering off the radio.  It reacquires the lock and I can re-run the calibration.  For me, I get anywhere from +2 to -4 PPB with the GPSDO and -1150 or so with the TCXO. 
    73,
    Len, KD0RC
  • WX7Y
    WX7Y Member ✭✭✭
    edited May 2020
    this is only on the 6700 my 6600 works great


  • Ed, K0KC
    Ed, K0KC Member ✭✭
    edited May 2020
    It appears that I have identified my problem with the Flex-6700 losing lock with the GPSDO. I sometimes have the 6700 running when I work 2 meter FT8 on my IC-9700 with no issues on the 6700 which stays locked to the GPSDO

    I also sometimes operate 6 meter FT8 with my IC-7700 while my 6700 is running. Today I noticed that the 6 meter RF (either in the shack or coupled into closely-spaced antennas) causes the Flex to lose lock. Once the Flex loses lock, I have to shut SmartSDR down and power-down the 6700 and then calibrate the 6700 against the GPSDO again after turning the 6700 back on and re-starting SmartSDR.

    In my tests today, the 6700 has stayed locked to the GPSDO for over 5 hours once I identified the problem and stopped operating on 6 meters. I plan to let the 6700 run overnight to see if it maintains lock.

    Apparently the RF on 6 meters adversely affects the 6700, but not the IC-9700 or the GPSDO. The solution for me will be to ensure that the 6700 is turned off when I operate 6 meters...I cannot address my antenna limitations at this point in time.

    Bret and Larry, this does not sound like the issue that you guys are experiencing, but I though that I would share my solution with you and the group just in case it helps.

    Ed, K0KC
  • KD0RC
    KD0RC Member, Super Elmer Moderator
    edited May 2020
    Good catch Ed. You might try some ferrites on the GPSDO cables if you have not done that yet.  Other cables could also be causing the problem, so don't stop at the GPS if the problem persists.

    73,
    Len, KD0RC
  • Al K0VM
    Al K0VM Member ✭✭✭
    edited May 2020
    I was also going to suggest trying ferrites on the wires/cables going to the GPSDO.. 
    Could also try bonding the case Hopefully metallic) of the GPSDO to same ground as the radio. And a 10mhz low pass filter on the ref input to the radio might also be helpful.

    AL, K0VM
  • Larry _ NY8T
    Larry _ NY8T Member ✭✭✭
    edited May 2020
    I choked everything on my gpsdo and divider, we will see.
  • Ed, K0KC
    Ed, K0KC Member ✭✭
    edited May 2020
    In some tests yesterday and today, my Flex-6700 has stayed locked to the GPSDO for at least 12 hours but lost lock overnight.

    In a test today, it lost lock on its own (without any RF in the shack) after only a few hours.

    To get it to lock again, I typically have to close SmartSDR, power down the 6700 and turn off the power supply for a short time and then restart the 6700, SmartSDR, and then run the calibration routine.

    I have not yet tried ferrites or grounding the GPSDO case, but the tests indicate that loss of lock occurs even without any RFI.

    Ed, K0KC

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