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Connect FT-891 to Laptop using CT-39 cable for FT8

Discussion in 'Working Different Modes' started by AD0IU, Apr 26, 2019.

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  1. AD0IU

    AD0IU XML Subscriber QRZ Page

    I'm attempting to connect my FT-891 to my Dell laptop using the CT-39 cable. I am using these diagrams provided by Yaesu:

    CT-39_Connections.jpg FT-891_Connections.jpg RTTY_DATA_Jack.png

    When I first looked at these diagrams together, I interpreted BROWN as GND; BLACK as DATA IN; YELLOW as RTYO. However, this connection resulted in only noise and no FT8 signals decoded by WSJT-X although I could hear them.

    So, I thought I maybe I had it backwards, and tried BLACK as GND (which made more sense to me); BROWN as DATA IN; and GREEN as RTYO. Again, no luck.

    I tried connecting an earphone to GND and RTYO in both cases and didn't hear anything. I tried adjusting the DATA OUT level from 50 to 75 in both configurations. Still no luck.

    Finally, I connected the laptop mic input to the front earphone jack of the FT-891. Success! I was able to decode. So my questions are:
    1. Which wiring scheme was correct? My guess is the first (BRN, BLK, YLO).
    2. Should I be able to hear audio in an earphone when connected to any of the output from rear DIN connector via the CT-39 cable?
    3. Would I be able to see some RTYO signal from the CT-39 by connecting my oscilloscope?
    4. Is there some other setting in the radio I need to adjust. I set it up for FT8 using the instructions here.
    Any feedback is welcome. This is my first foray into digital modes beyond CW. I'd like to utilize the CT-39 cable if possible. I'd like to get the receive part squared away before attempting transmission.

    73,
    Rob
    AD0IU
     
  2. AD0IU

    AD0IU XML Subscriber QRZ Page

    Update - discovered the DATA OUT level was transmit power based on some more reading.
     
  3. AD0IU

    AD0IU XML Subscriber QRZ Page

    I sampled the output from the DATA jack with my oscilloscope and compared it to the output from the headphone jack.
    The wave forms were similar, although the output from the headphone jack was smoother overall.
    Additionally, the output from the DATA jack was 20 microvolts, while the output from the headphone jack needed to receive FT8 on my laptop was 0.02V.
    No amount of fiddling with my laptop sound settings brought the input from the DATA jack up to a point where I could receive the signal. Looks like I'm going to have to get some sort of interface.
     
  4. AD0IU

    AD0IU XML Subscriber QRZ Page

    So I got the receive portion working. Connected the headset jack of the rig to the input of the computer and had great success.
    Got an SC-17 on the way and will continue experimenting.
     
  5. AD0IU

    AD0IU XML Subscriber QRZ Page

    Got receive working via cable from FT-891 headphone jack to laptop input. SC-17 on the way for more experimenting.

     
  6. K7MH

    K7MH Ham Member QRZ Page

    The Yaesu SCU-17 should solve all the problems you are having.
     
  7. AD0IU

    AD0IU XML Subscriber QRZ Page

    You were absolutely right! Took me awhile to get it squared away with the connections and the laptop settings, but now I'm in business and have had 3 contacts so far.

    Cheers & 73

    Rob
     

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