Video: Oscilloscope Balanced Antenna System Tuner Performance Test

Discussion in 'Amateur Radio News' started by KA0KA, Sep 1, 2018.

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  1. KA0KA

    KA0KA Ham Member QRZ Page

    Thanks, ya well do, many of them are completed now, I will have music in them but as you, I think said on my youtube channel comments I will try to lessen the main tracks, prob only include it in the end where I choreographed the still photos with the music! Remember this was my first video creation!
    I will try to show topics to me, that are rare to non-existent that people would really benefit from! I did hook up a voltage divider I made to the balanced line and ran legal limit, I could add that into some addition possibly... no difference in my system!
    Last edited: Sep 7, 2018
    K9FV likes this.
  2. WR2E

    WR2E Ham Member QRZ Page

    Tyler, why is voltage balance important?
  3. KA0KA

    KA0KA Ham Member QRZ Page

    Remember, a scope in its native form is only a volt and time indicator, there this is actually a complex three part AC signal [Xc; Xl; R] summed to [ Z ] where the point of termination on the feedline is maintaining a static phase and amplitude when F1 is also static. Both [ V ] and [ I ] are separated in phase on the feed line, but maintain a proportional relationship under these static conditions.

    We can then look at the relationship of AC voltage and phase to measure what I would call destructive interference or constructive interference, this is the simple summing of both amplitude and phase.

    When a line (or system) is balanced, the respective separation in voltage and current will maintain a 180 degrees destructive relationship between the two lines, this ideal situation is then how one part of the antenna system works to get you on the air!

    On the second half of the video I use the ‘add’ button to bring both CH1 and CH2 summed together to demonstrate this, hopefully bringing something more to the demo... Great question, I hope this simple explanation helped a bit!
    Last edited: Sep 7, 2018
  4. WR2E

    WR2E Ham Member QRZ Page

    Thanks. Is it possible for the signal on each line to be balanced in amplitude and phase and the current to be unbalanced? For example; let's say the antenna is actually unbalanced for some reason. Maybe one side is closer to ground or other objects. If the voltage is balanced and in phase, could the current be out of whack?
  5. NK4K

    NK4K Ham Member QRZ Page

    Well, think of all the TV shows that have program music during the main action (NCIS) and some that don't but have it during the transitions (BlueBloods). Both have music during the intro and the outtro. Remember, too, that this is amateur radio and not amateur video, so I doubt more than 0.05% of the respondents have produced a serious video of even 15 minutes or longer. The textbook for the broadcast school here insists on program music. And, I gotta tell ya, I doze off without it.
    Some just hate music, don't understand it, and refuse to change. Others of us who are musicians for over 50 years live otherwise.
    Bottom line: It's YOUR video. Do what you want. Listen to your inner artist.
    N7TH and KA0KA like this.
  6. KA0KA

    KA0KA Ham Member QRZ Page

    I agree 100% and there could be a generational difference, most people are nearly 70 plus years old I speak to, I am in my 30's so, there is a stylistic difference I think as well. Remember this is just a hobby, a rather unknown one these days... :(
  7. KA0KA

    KA0KA Ham Member QRZ Page

    This is really a very effort consuming task, first you would have to check each part of the system independently, the ant at the feed point, feed-line its self and transmatch.
    Symmetrical tuners are less suspect and placing the Balun on the input does not guarantee that it’s forcing equal current into the line. The ground reference of the system parts also matters, if any... so yes anything is possible.
  8. AG5CK

    AG5CK Ham Member QRZ Page

    I think so. One leg of my doublet runs adjacent to a tree and the other is in the clear. Using a balanced L tuner I can adjust the taps on the tuner for balanced current. Before figuring this out I had terrible rfi on 20m. Now I have no issues even at legal limit.

    At first I thought I made one leg too long so I double checked that. On the lower bands the left side needs more L than the right and it's the opposite on the higher bands.

    I'm not a fan of using a balun on either end of an unbalanced tuner with balanced feedline. Not saying it doesn't work. That's what most people use with balanced feeders .
  9. WR2E

    WR2E Ham Member QRZ Page

    So by carefully balancing the CURRENT on the feedline you were able to mitigate feedline radiation that was causing RFI.

    That goes along with what I've been reading elsewhere.

    Seems that the VOLTAGE on the feedline can still be balanced, yet the CURRENT not be, and the feedline will radiate.
  10. KA0KA

    KA0KA Ham Member QRZ Page

    I have found with the experiments that the currents can be balanced in amplitude and out of phase resulting in feed-line radiation, but each time when I switched from current to voltage viewing there was always a direct proportion from one to the other [ V ] and [ I ]. At no time was I able to achieve a test where the voltages and currents did not have a proportional value in amplitude and phase they were always synchronized at some level. I think this has to do with my first response to WR2E. It is really interesting to actually 'see' this in real life.

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