Testing Aircraft Antennas-Standing Wave Ratio

Discussion in 'Instruments / Avionics / Electrical System' started by Flyhighdave, Nov 10, 2016.

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  1. Nov 10, 2016 #1

    Flyhighdave

    Flyhighdave

    Flyhighdave

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    I have installed several copper foil antennas in my project (nav, comm, glide slope) and would like to test their function with a swr meter (standing wave ratio). If I understand correctly, the swr meter is hooked up in series in between the transmitter/receiver and the antenna. I am wondering if a handheld type nav/com would serve the purpose for this test. Any advise is much appreciated. Thanks! David
     
  2. Nov 10, 2016 #2

    rick9mjn

    rick9mjn

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    yes a handheld will work.......a good way to learn more about this question ,is to do a google search on Wikipedia for "SWR meter". ............................................................................. good day rick/ ................... IMHO-IMBW,i my humble opinion,i may be wrong
     
  3. Nov 10, 2016 #3

    Aerowerx

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    Yes, it will work. But be sure to use an SWR meter made for VHF use. One made for CB (Citizens Band) will give inaccurate readings.
     
  4. Nov 11, 2016 #4

    Flyhighdave

    Flyhighdave

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    Thanks for the advise, Homebuilders. This group is great! I'll move forward with my antenna testing. David
     
  5. Nov 11, 2016 #5

    Derswede

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    Check and see if there is a local amateur radio club. A standard VHF SWR bridge is what you will need, and I'd bet you could borrow one easily enough. Aerowerx is correct, the cheap CB meters are normally good to max 50 MHz, in my experience. If anyone in the Winston/ Greensboro NC would like to do this, I do have such a meter and will make it available if needed. Just PM me and we can meet somewhere.

    Derswede
     
  6. Nov 11, 2016 #6

    Aerowerx

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    So do I, in North Central Ohio.
     
  7. Nov 11, 2016 #7

    BoKu

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    I keep seeing folks say that, but my personal experience indicates otherwise. I use one of those Radio Shack cheapies to tune my antennas, and its numbers seem to correlate well with overall antenna performance. It might not show a numerically accurate SWR, but it certainly seems to show accurate relative values for comparison between antennas (is my homemade antenna as good as this factory antenna) or between configurations (is this length better than that length).
    --Bob K.
     
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  8. Nov 12, 2016 #8

    PW_Plack

    PW_Plack

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    Then you won a crap shoot. It happens. But the danger remains that if your SWR is too high, the final output stage of your transmitter can be damaged.

    A handheld radio can be used, but it may not have adequate carrier power (typically 1 - 1.5 watts for a handheld) to drive the meter to full scale in the calibrate position. Five watts is a safer bet.

    The best answer is an antenna analyzer covering VHF. It's much faster, doesn't use your aircraft radio, and puts only a tiny signal through the antenna to reduce the risk of interference. Your local ham radio club will either have one, or have a member who has one. Mine is an MFJ 269, and I'll be happy to help test NAV or COM antennas on experimentals in the Salt Lake area.
     

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