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Hexbeam receive audio

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W1SFS, Oct 26, 2020.

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  1. W1SFS

    W1SFS Premium Subscriber QRZ Page

    I recently acquired a used K4IO hexbeam. I put it up on a 30ft tower with a Yaesu G450 rotor, new coax, new choke balun approximatley 150 ft run of coax to the shack. Once it was up, SWR is above 4:1 on 20 meters. lowest SWR is about 2.5:1 on 10 meters. Compared to my G5RV, an S9 signal drops down to 0 on the meter, and audio is much lower even when the beam is pointed toward the other station.

    I've checked everthing I can think of and Google hasn't offered any suggestions. Every comment or forum just talks about what a great antenna it is. It seems like I am the only one having a problem with it.
     
  2. NG1H

    NG1H XML Subscriber QRZ Page

    I wouldn't say "great" but it is a pretty good antenna. But everything has to be built to spec or you will get all sorts of problems. Just one of the elements installed incorrectly can throw off 3 or more of the other bands. Unfortunately you will probably have to take it down to troubleshoot. Here's what I would do:

    1) Test all the feedpoints and element ends for continuity.
    2) Measure the spacing on all of the loops holding the wires. Including the reflectors. Adjust as needed.
    3) Find some way to mount it at least 12' above the ground. Test all of the bands. SWR will be somewhat high due to it being so low but as long as the SWR is below 3:1 on all of the bands you should be fine in the air. Otherwise you will need to tune. Note that adjusting one band will affect other bands.
    4) When you install back on top of the tower make sure the antenna is away from other structures, the roof, etc.
     
    WB5YUZ, WA7ARK and AK5B like this.
  3. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    reconsidered.

    Something is either connected wrong, or broken or not making contact. Take it down and go over it piece by piece. Good luck!
     
    AK5B likes this.
  4. W1SFS

    W1SFS Premium Subscriber QRZ Page

    Thanks, I was afraid I would have to take it down and trouble shoot. I guess now is better than later since the weather is still tolerable.
     
  5. VK3TEX

    VK3TEX Ham Member QRZ Page

    Carefully follow all K4KIO specs when assembling antenna.

    Use only the ferrite rings supplied with the antenna as a balun choke. Not sure what new one you have but that may be the issue.

    Yes, they are great when they work!! I have had one up for four years and it is a great performer....

    If all else fails, contact K4KIO for any troubleshooting tips.

    Good luck, and let us know how you go!

    Les VK3TEX.
     
  6. W1SFS

    W1SFS Premium Subscriber QRZ Page

    Thanks Les,
    I wondered if the choke was causing a problem. Leo noted in his assembly instructions that any RF choke will work so I ordered an MFJ from HRO. I noticed when I assembled it (it was partially assembled from the gent I bought it from) there was a small piece of L shaped aluminum inside the center post, almost like a shim, with a hole for the bolt to secure the center post to the stub on the base plate. I wonder if that could be causing a short somewhere along the center post? I didnt see any mention of that aluminum shim in the assembly instructions and I can figure out what it would be accomplishing.

    Jason
    W1SFS
     
  7. KC2PMM

    KC2PMM Premium Subscriber QRZ Page

    My K4KIO hex beam did not have any shim on the center post. It is actually on a short section of PVC or other plastic part to insulate the center post from the spreader plate.
    Guy
    KC2PMM
     
  8. VK3TEX

    VK3TEX Ham Member QRZ Page

    Hi Jason,

    I think something within the centre post may have come off, that L shaped shim may be bolted to something internally down it.(?)

    Don't know....

    I'm not sure what type of choke you ordered but the originals are just a series of 8 Ferrites slipped around the coax cable near the top plug
    which goes into the HEX. Just to stop common mode currents...(I taped mine to the coax with electrical tape to stop them moving)

    Send a photo to Leo, K4KIO and i am sure he will be able to identify what that shim is and where it belongs if anywhere...

    Cheers, Les VK3TEX.
     
  9. W1SFS

    W1SFS Premium Subscriber QRZ Page

    Thanks for all the suggestions, after three tries I finally got it up and working this past Saturday. After determining that a loose center post was the likely culprit, I attempted to raise it. A spreader got caught on a tree limb and pulled the spreader apart. Lowered it again, fixed tested and re-tested. Third time was the charm. Made two contacts to Texas on 20 meters and Brazil on 17 Sunday.
     

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  10. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    In my experience, this step finds probably 90% of antenna/feedline problems, and it is simple and easy to do. I keep my antennas on the air this way. I don't even own a Nano VNA or a app-driven antenna analyzer!
     

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