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how to use 'iq" signal

Discussion in 'General Technical Questions and Answers' started by W9WQA, Nov 17, 2019.

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  1. W9WQA

    W9WQA Ham Member QRZ Page

    the radio has iq output. how do i use that to get to a bigger display?
    i know nothing about this...
     
  2. KB7WG

    KB7WG Ham Member QRZ Page

    You can feed the IQ output into your computer sound card. Normally line in, but mic in can sometimes handle a weaker signal. And then, SDR software can analyze a bandwidth of IQ data. That bandwidth will depend on your sound card sampling frequency. It can be adjusted.

    Most SDR software has a IQ input function. And many other free programs can handle and display IQ signals from your sound card.

    It's really neat stuff, make a jumper and check it out. It displays frequency spectrum and the "waterfall"........and other functions and measurements.

    Direct IQ detection has many advantages over other detectors.
     
  3. W5DXP

    W5DXP Ham Member QRZ Page

    If it is an Xiegu G90, you will probably have noise problems when displaying I/Q with the PC line input on the internal sound card. Note that the I/Q input requires a stereo line input (or stereo mic input), not a mono mic input.
     
  4. W9WQA

    W9WQA Ham Member QRZ Page

    usb? laptop?
     
  5. K7TRF

    K7TRF Premium Subscriber QRZ Page

    On a laptop you'll either want to inject the IQ audio stream into your microphone input or use an external USB soundcard that plugs into a USB port as most laptops lack a line input jack for bringing audio to the sound card.

    Older laptops tend to use a simple 3.5mm (1/8 inch) mono or stereo jack for mic input but it seems many newer laptops use the three circuit (4 electrical connections) 3.5mm jacks that carry both microphone and headset audio in a single jack. Conversion cables are available to break out the mic circuit to its own connector. All my laptops are PCs, I don't know how Macs handle audio in and out these days.
     
  6. W5DXP

    W5DXP Ham Member QRZ Page

    Please note that since two of those three circuits are used for stereo audio output, that leaves only a mono mic circuit for audio input. I/Q signals require stereo inputs so those newer laptop built-in sound cards cannot be used. StarTech makes USB external sound cards with stereo line and/or mic inputs. In particular, this one has stereo mic inputs with a sample rate of 96k which will decode an I/Q bandwidth of 48k.

    https://www.startech.com/Cards-Adap...verter-External-SPDIF-Sound-Card~ICUSBAUDIO2D
     
    K7TRF likes this.
  7. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Good point, I've used simple audio inputs to newer laptops but true I/Q wouldn't work via the headset port as you point out. I guess with a laptop like that you're forced to an outboard USB sound card that accepts stereo audio inputs.

    If the rig IQ output is line level, something like this could work: https://www.fullcompass.com/prod/14...MIgoyi3Pbx5QIVVBx9Ch1heAqBEAQYASABEgIS1vD_BwE
     
  8. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    If you have an X-Y oscilloscope, plug the I signal into the X channel, and the Q signal into the Y input, and see some really cool stuff.
     
    W6KCS likes this.
  9. W9WQA

    W9WQA Ham Member QRZ Page

    ha, i can do that, like ntsc color and stereo alignment.
    thinking thats where i heard of "iq" before
     
  10. KB7WG

    KB7WG Ham Member QRZ Page

    "IQ" is a modulation/demodulation technique. It's a way to detect changes in a signal and to impress changes on a signal. Digital software, DSP, uses IQ signals.

    There is another interesting effect. Let's say that you are in a cw pile up. Normally one would use a skinny filter to concentrate your ears on your contact.

    IF you IQ that cw beat..........and put I in one ear and Q in the other........the signal will form a virtual location between your ears......and if there is another signal there......it will have a different location........giving your mind another reference to separate the signal.

    Does that make any sense?
     

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