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Logmag

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W4BIB, Jun 14, 2021.

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  1. W4BIB

    W4BIB XML Subscriber QRZ Page

    What is logmag? I just built a ZS6BKW. The yellow line is the logmag thing and the blue line is the SWR. It looks like I have a lot of tuning to do
     
  2. W6KCS

    W6KCS Ham Member QRZ Page

    On a network analyzer, log mag is either a two-port plot of insertion loss in dB, or a one-port plot of return loss. Basically instead of showing SWR, it shows how much of your signal (in dB) doesn't return to the radio. The more loss, the better. 14 dB is about 1.5:1 SWR. Here's a log mag plot of the return loss of a VHF low band antenna. I picked a poor color to plot, sorry about that. It looked good on the front panel with a black background :)

    sinclair low band.jpg
     
    Last edited: Jun 15, 2021
  3. AK5B

    AK5B Ham Member QRZ Page

    Sounds like a small transmitting loop that has fallen over onto the ground, kind of like a LOG except smaller with variable tuning... A bettter term would be MagLOG):D
     
    M0AGP likes this.
  4. W9IQ

    W9IQ Ham Member QRZ Page

    Put another way, logmag when used with an antenna measurement is the same as return loss. Return loss is another means of showing SWR. You can directly convert from SWR to return loss and vice versa.

    - Glenn W9IQ
     
  5. W4BIB

    W4BIB XML Subscriber QRZ Page

  6. W4BIB

    W4BIB XML Subscriber QRZ Page

    im not sure why my photo wont upload
     
  7. W4BIB

    W4BIB XML Subscriber QRZ Page

    [​IMG]
    [​IMG]
     

    Attached Files:

  8. W7UUU

    W7UUU Principal Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    You're linking to your "Google Photos"

    You need to use the "Upload a File" button (not the "image" button) then point to the file on your OWN computer. It will then upload here

    Dave
    W7UUU
     
  9. K8JD

    K8JD Ham Member QRZ Page

    I don't have any luck loading an image file fom my computer to a post I make here !
     
  10. W6KCS

    W6KCS Ham Member QRZ Page

    It looks like a return loss plot, with several dips indicating high return loss, i.e. very little signal being reflected.
     

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