Is My 160-10 Meter Balun Attenuating My Received Signals ?

Discussion in 'The Low Bands - 630/2200 Meters - VLF' started by K2WH, Apr 1, 2018.

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  1. K2WH

    K2WH Premium Subscriber QRZ Page

    I have been successfully receiving signals on both new bands with my Yaesu FTdx3000 but as I sit here receiving 2200 meters, with one decode, it just came to me; Hey, is my balun killing some of the weak signals coming down my window line through the balun and then the short run of coax.

    Well what do you think? Should I install a jumper around the balun?
  2. K2XT

    K2XT Premium Subscriber QRZ Page

    Just off the top of my head I can't think of why the LF bands should be any different than other bands, meaning if you can hear band noise then whatever attenuation there is is not hurting you.

  3. K2WH

    K2WH Premium Subscriber QRZ Page

    Well perhaps I should have included the fact that the balun is rated from 160 meters to 10 meters !

    It is NOT rated for 630 or 2200 meters.

    IOW, I suspect above 160 meters there may be some attenuation.
  4. K2XT

    K2XT Premium Subscriber QRZ Page

    Bill, your receiving system may be able to tolerate the loss from the balun. That's why I suggested the simple test of removing the antenna and seeing if the noise goes down. If it does then you are hearing down to the noise level.
    Now in these times that may not be enough, since the digital modes can copy signals below the audible noise level but it will give you a good idea -much better than believing the label on the balun.
  5. K2WH

    K2WH Premium Subscriber QRZ Page

    Thanks for the suggestion on the test.

    I realized that simply switching my coax off my Yaesu rig, I could accomplish that and there is a significant reduction in noise level when disconnected.

    The noise level goes to essentially zero with the coax disconnected and back up to about an S3 when reconnected on both bands.


  6. WB1E

    WB1E Ham Member QRZ Page

    41 Balun.png balun_4-1_image4_0.2-50mhz.gif

    Lets say it is a 4 to 1.....
    Looking at this image one can see how the shield cancels the 1:1 impedance match, so....with the shield removed, it's straight through. There may be however some effect that the coiling of magnet wire on a ferrite that I can't comment on right now.

    What I do know for sure is that with a simple oscilloscope scope (or very good milivolt meter) and a signal generator set to the frequencies of interest, you can test the loss across any band you like. That IS as long as the represented indications from the Oscope are flat across the spectrum that your are looking at.

    I may try this myself as soon as my new shack is back up and running. :)

    Doug QRZ is not working well, so please excuse errors is this post
    Last edited: Nov 19, 2018
    W1TRY likes this.

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