IQ phase shift module

Discussion in 'Homebrew and Kit Projects' started by N5HXR, Apr 6, 2021.

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  1. N5HXR

    N5HXR Ham Member QRZ Page

    After you guys helped me in putting together a simple receiver, I thought I should try to make a phase shift module to achieve sideband rejection. I grabbed the schematic from EMRFD figure 9.56, and adapted it.


    I don't have much in the way of precision resistors, so I did what I could with DMM matching. To make the oddball values, I had to write a program to calculate series and parallel combinations that would get me close... I can't get the 1% precision values that the EMRFD authors suggest, but I feel like I did OK given what I have on hand.

    Construction went OK -- I went with only one isolation routing pass, which required a lot of cleanup. So I'll stick with the 2-3 passes I've used in the past. Anyway, after some work with a scalpel, it came together alright:


    I didn't have any 6k8 0805 resistors, so I bodged in some 1206s (making for some solder blobs and two unsightly wires), but my construction is improving, I think. A lower iron temperature and more flux seem to have helped.

    And testing with a signal generator shows about 34dB of sideband rejection (if I'm doing my math right), and it seems to work OK. I'll have to get some higher precision resistors, though, and now I see why people buy fancy bench-top multimeters!

    AB2YC, KA9JLM, W7UUU and 3 others like this.
  2. VK4HAT

    VK4HAT Ham Member QRZ Page

    Nice work Josh.
    N5HXR likes this.
  3. AJ4SN

    AJ4SN Ham Member QRZ Page

    Very nice! Thanks for sharing this project.
  4. N5HXR

    N5HXR Ham Member QRZ Page

    Thanks! The brown truck of happiness just brought me my 0.5% precision resistors (and of correct value, too!) so I can make an even better one.

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