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EME with Flex 6500 + Transverter; Rig Control Error using doppler shift in WSJT-X V1.80



  • Marc LalondeMarc Lalonde Member
    edited November 2017
    HI that my 2 cent

    until my radio hardware die , was very successfully on 144 EME  whit my 6700
    that some tip lean hard way , and by the way never got DAX issue 
    issue i have was cause to Radio hardware failure  

    AGG-T set to max 
    AGC to Fast 
    absolutely no DSP function enable
    Pre-amp +40db

    but the most critical that take me long time to understand 6700 is a really bad VHF radio !!   noise figure is 9db !!!!  ,so you absolutely need a good pre-amp whit at least 
    20db gain  and naturally under 1db NF  , usually that is overcome by the 2MLDPA
    so no one notice the lack of sensibility  ,but on my setup i not use it since my linear take 8dbm for 800W output 

    next critical step is control  out of band signal , i notice that local FM radio 102MHZ
    combined whit local pager  make intermod but also increase noise floor up to S5-6 
    after put very sharp helical resonator filter in front of the WA2ODO pre-amp  (that is also very narrow bandwidth) noise floor drop to S3 ,so increase of noise floor was due to mixing of strong signal inside the radio !!   naturally i need very low NF pre-amp for
    compensate insertion loss of the Filter  ( 1db loss + 0.5db coax loss + 0.2 NF pre-amp  = ~2db NF ! )

    but one you got good external pre-amp whit very selective input  it good performer
    on first week of ARRL EME Contest , i do 49 station  ,actually i able to work almost
    any station whit 2 x 10 whit 800W and more  , i do 94 grid in less that 10 day of operation ,before radio Hardware failure 

    hope to see you on the moon soon 

    Best regard  Marc  VE2PN

  • Marc LalondeMarc Lalonde Member
    edited November 2017
    also WSJT-X setting is critical   , this is what i use on my side 

    Sync - 1 
    F Tol 20 
    Decode DEEP
    Enable averaging 

    that my gain and 0 setting of wide graph whit my "usual" signal decode threshold

    also for finish you use a flex so use it ;-)  , here i operate whit WSJT-X 
    and monitor whit WSJT10  and sometime MAP65  each have it own CAT port
    personally  X version decode 95% of the time ,and back up to 10 for segnod signal 

    finally forgot the SmartSDR panadapter WSJT is much more sensitive you will probably only see I2FAK signal ;-) 



  • WolfWolf Member ✭✭
    edited November 2017
    OK - I will try all of that. 
    The below attached recommendations as well .

    Let me say thank you for all your contributions !
    And hopefully see you on the moon very soon.

    73 - Wolf

  • Bill - ND0BBill - ND0B Member
    edited November 2017
    I have been busy with work so just getting a chance to look over the responses here.   Two comments...

    John - K3MA.    I did not elaborate on how I am working EME.   I use a single 12 element fixed elevation Yagi during my moonrise and moonset taking advantage of the flat terrain and low noise around here (see https://www.youtube.com/watch?v=uIQqZL_3xR0 for a presentation I did on this at Dayton 2012.)    As a consequence I have NO margin between my station working on EME and it not.   If you are running a 2x or 4x station the issues I am seeing are likely being hidden but the 3dB or 6dB of gain you have over my setup.    I have spent a lot of time trying to chase down what happened and keep coming  back to it was likely in conjunction with a software update.   Since that time WSJT (NOT x) waterfall when adjusted to the noise floor here has regular vertical artifacts that do not move with frequency. I have come to believe these are introducing a couple of dB of additional noise I need to overcome.   I would contend whatever the issue is could possibly be affecting how low level of station you are able to work.  You can work most of them but what are you leaving behind?  

    The assertion that AGC adjustment can solve the issue:    I find this not very likely.   I have always ran with AGC off and am looking for signals that RARELY, even for strong signals, are audible or visible in any way on the radio panadapter or waterfall.   WSJT makes a loose calculation of the relative strength of the signal it is decoding (singular for EME operators using WSJT) compared to the noise and other signals in the rest of the passband.   With no signal present the attempted decode by WSJT shows -33.   A decodable signal is usually around -27 dB although when I first had the 6700 this had moved up to -28dB.   A signal you can hear in the speaker or in any way manner or form detect the presence of without WSJT, VERY rare, starts kicking in around -18 db... this is a VERY strong signal for single antenna EME.   So... what would AGC act on and to what purpose for the vast majority of the EME signals that are neither audible nor visible on the radio?   

    On a whole another, but likely related issue, I was flagrantly reminded yesterday of just how flawed DAX is in both directions is while operating 30m FT8.    I received the following along with a couple of nasty emails (which I have gotten used to and have a fairly standard thank you I send)
    221200   3  0.3 2336 ~  ND0B OVERDRVN    

    This is not the first or these I have seen nor will is it likely to be the last
    085115  -3 -0.4 1016 ~  YOUR OVERDRIV 

    Except this is not operator error, it is a DAX issue as stopping and restarting DAX instantly fixes the issue.   One kind soul even sent me an email yesterday thanking me for correcting my overdrive issue after I stopped and restarted DAX.  

    I do a lot of 6m meteor scatter and generally use an RTL dongle and SDR Console for RX there.  As a consequence I can self monitor.   When this issue happens I immediately know it as I start self decoding for a sequence or two (indicating some kind of extra delay) as well as audibly note that that transmit audio is distorted.  

    I joke about having an $8k transmitter but seems even with that there are issues.

    73 de Bill ND0B

  • WolfWolf Member ✭✭
    edited November 2017
    Just to give a quick feedback and to say thank you again !

    Today I saw NC1I on 70cm EME with WSJT -13 dB. Thin spoors had been visible on the Flex. Strong on WSJT.  Looks like I'm getting close . . .

    What did I do ?
    Flex6500: AGC = off and full amplification - no other changes.

    Power supply of transverter: The linear voltage regulator produced noice - pretty strange . . .  Has been replaced.

    And the last one was the most disturbing: I run 2 high definition monitor screens driven from a high resolution graphic card in the PC (something that came from my kids old gaming PC).
    The monitors produce a spectrum on 70 cm and even stronger on 144 MHz. Depending on the frequency even broadband 60 Hz modulation is visible on the WSJT waterfall - nothing visible on the Flex.
    That was the sensitivity limiting factor !
    Now I use a MacBook Pro with Parallels and this issue is gone.

    So - my Flex is fine . . . !

    Again -thank you !
    Wolf - DF7KB

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