Turning FT-991A into a real SDR.

Discussion in 'Amateur Radio News' started by PY2RAF, Sep 13, 2019.

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  1. PY2RAF

    PY2RAF XML Subscriber QRZ Page

    What about you plugging your radio's USB port to the computer and obtaining the Audio, the CAT and... The digitalized spectrum I/Q SDR output to be used with a Panadapter or with your favourite GNURadio application? With no external wires, jumper wires or a external SDR?

    Of course some may say that we are talking about some Apache Labs or Flex Radio.

    Well, no - This time we are talking about a FT-991A.

    After a few months of research, discussion and a lot of constructive feedback, I was able to actually embed a RTL-SDR dongle inside the FT-991A and exporting its interface through the radio's USB port - No external extra wires, ports or whatsoever - Everything coming down neatly from the existing USB port, along the CAT and Audio interfaces.

    The enterprise is 100% open source with schematics, BOM, board gerbers available at https://github.com/rfrht/FT991A-PAT/ and thorough documentation is available at https://github.com/rfrht/FT991A-PAT/wiki.

    The project was featured in Hackaday and RTL-SDR Blog.

    A demonstration of the working setup can be watched in the below video:

    This mod is also feasible for a IC-7300 without the need of replacing the USB hub - the idea is just the same: Tap the voltages, the signaling, the IF output, hook it to the panadapter board, lodge the SDR in the radio, solder the SDR USB port to the USB hub - And result is going to be pretty much the same!


    - Rodrigo, PY2RAF.

    Attached Files:

    K0DHO, N1NA and KK4CUL like this.
  2. KE1THE

    KE1THE Ham Member QRZ Page

    If I didn't want to do all the soldering how can I make this happen today (I don't care if there are wires).
  3. PY2RAF

    PY2RAF XML Subscriber QRZ Page

    Hi Brian!!!

    You have two possible paths:

    1.1) Do the soldering stuff and build your own (technically superior) panadapter, the instructions are all in https://github.com/rfrht/FT991A-PAT/wiki
    1.2) Buy a G4HUP panadapter (the PAT70M from https://www.sdr-kits.net/index.php?route=product/category&path=66_73_84) , and jump to Step #7 in the above instructions
    2) Run the wire externally as per https://github.com/rfrht/FT991A-PAT/wiki/appendix-assembly-variations


    - RF.
  4. WB2LSU

    WB2LSU Ham Member QRZ Page

    Thank you for all your work on the 991a. Just bought this radio brand new and what you have done is very impressive. 2 issues: voiding the warranty and could you post a video of before and after on SSB and hearing the difference. Also a video on your actual install work. Would love to see Yaesu do this as an upgrade. Bruce
  5. G8FXC

    G8FXC XML Subscriber QRZ Page

    The 7300 does not have an IF - it is direct sampling.

    Martin (G8FXC)
  6. PY2RAF

    PY2RAF XML Subscriber QRZ Page

    Hello Bruce, good morning- and thank you very much for the kind words!

    1) Indeed, I voided my warranty, sure thing. But got a heck of a radio ;-)
    2) You can see any differences on radio sensitivity with and without the signal tap in this video:

    Spoiler alert: None noteworthy.

    3) With regards to the actual install work, unfortunately I don't have any videos head-to-tail on that. I do have instructions on how to o the whole thing on this github page: https://github.com/rfrht/FT991A-PAT/wiki/

    Some pictures are missing because they are hosted in a server at my apartment - which is undergoing a renovation/construction and the server were removed - it will be some more weeks out of order.

    Feel free to reach, will be more than happy to help!
    WB2LSU likes this.
  7. UB3DTI

    UB3DTI QRZ Member

    PY2RAF, good time of day.
    Question about the usb hub: 3 outputs D+, D- and Enabled are signed in the photo. Actually, did you somehow use the Enabled output? For example, they fed 3.3V to it through a resistance of 10k or paired it with a control pin of 2 or 3 hub ports? With best wishes. UB3DTI, 73!
  8. W9WQA

    W9WQA Ham Member QRZ Page

    how about just a block diagram sketch to show rig/mods...?tnx
    not fancy !!
  9. UB3DTI

    UB3DTI QRZ Member

    I don't know what to do with the output of the Enadle ... To pair it with the 16 or 12 pin of the hub or apply 3.3V to it through a 10k resistor. Or maybe it should not be touched? UB3DTI 73!

    Attached Files:

    • hub.jpg
      File size:
      1.6 MB
    PY2RAF likes this.
  10. PY2RAF

    PY2RAF XML Subscriber QRZ Page

    Priviet UB3DTI!!

    short answer: you don’t need the enable pin - and sorry for that.

    long answer.:

    so- that ORIGINALLY was designed to control the power state of the panadapter board: originally, that wire would be carried to the Enable pin of the panadapter board voltage regulator - which would only power on the panadapter AND the SDR dongle upon plugging the USB port in a computer.

    however, that idea was quickly abandoned for the following reasons:

    - originally the SDR was powered by a 5V line in the panadapter board. However, due to the SDR power consumption and the inability of using a switched power supply (noise generation inside the radio isn’t a great idea), the linear voltage regulator dissipated A LOT of heat. Then instead, I tapped 5V from the radios voltage regulator.

    - unneeded complexity - as the SDR gets in a quiescent state while not initialized by the driver.

    So there was no real gains and just abandoned this design idea. And didn’t replace the picture.

    I’ll make a note about that in the wiki - that could have spared you the hassle of wiring that one on that QFN IC.

    I don’t have any better pictures, thus the reason I didn’t change the picture in the wiki.

    If you have any further questions please get in touch.

    my best regards

    Last edited: Jan 15, 2022 at 10:25 PM

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