Fixing the Hexbeam … again

I posted about three weeks ago about my Hexbeam failing again and you can read that by scrolling down the page a little or by clicking here.  I spoke to the manufacturer directly after and he sent me a set of his new custom made PTFE spacers.  There was a contest the following weekend so I managed to get the mast down and replace the spacers on the broken element in time.  I didn’t do any other elements as it started to snow!

When I lowered the mast, this is what I found (click for full size version).

The burned out end of the 15m element on my Hexbeam

The burned out end of the 15m element on my Hexbeam

Not only had the end next to the driven element burned out but the other end of the cord had disconnected from the spacer and I found it on the floor under the mast.  It was a major failure.

Today is the first day that there’s been really favourable weather and so I was able to replace the insulators and cords on all the other elements.  It’s the EA RTTY contest this weekend and I’m hoping to make a single band 20m entry.  It’s a good job I did the aerial work today as the 20m element was on the verge of failure.  I don’t know exactly when this happened but I don’t think it would have lasted much longer because as you can see, the cord has completely burned through and it was hanging on the heatshrink.

The 20m element on my Hexbeam, hanging on by the heatshrink

The 20m element on my Hexbeam, hanging on by the heatshrink

The latest modification is a bit sturdier than before.  Each piece of wire, driven element or reflector has a terminal ring on the end.  Previously a piece of cord was fed through that ring and heatshrinked in place.  Now the ring goes into a PTFE spacer and heatshrink is applied to keep it all together.  Here’s an element in place with the heatshrink ready to go on.

Teflon spacer on the end of the Hexbeam element

Teflon spacer on the end of the Hexbeam element

The heatshrink is pushed up over the PTFE and shrunk into place (blurry pic, it’s really quite difficult to focus on these elements in situ, hence the brown cardboard background).

New spacer all heatshrinked and ready to go

New spacer all heatshrinked and ready to go

And finally here’s the 17m, 15m, 12m and 10m elements all modified, you can just see a small part of the 20m element at the top of the picture.

Modified Hexbeam elements

Modified Hexbeam elements

I don’t know for sure if the problem is fixed, only time will tell.  I like the Hexbeam design a lot but I’m not a great fan of the way it’s kept failing on me.  However the customer support from the manufacturer has been fantastic all the way through and I can’t fault that.

4 Comments

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  1. Corona burns? How many kilowatts are you running? Folding the end of the wire back an inch to form a loop may take the heat away from the cord perhaps?
    Ian

    1. Kilowatts? I wish! Just 400w, Ian and it’s a known problem when running data at very high duty cycles in the wet so it’s specific circumstances. Both the manufacturer and myself are hoping that this lastest mod will resolve it.

      73 Keith.

  2. It really a simple answer why these Spacer ropes burn on the Hex Beams !!
    When the ropes collect moisture and salts they become Resistive and begin to heat up and melt with RF, say with 500Watts and Higher Levels !
    NA4RR, DX Engineering, etc and others use this cheap attachment approach and many near Salt Water find that this happens on most of the Bands in the Hex Beam and is simply a Poor Design practice to simply crimp the Spacer Ropes to the Antenna Elects
    Wake up and Smell the Smoke !
    It a bad Design Approach, the ropes have a Carbon filler to color the Ropes, add Water, Salt and RF and they melt and caught on fire ! It’s Physics 101 my folks !
    Cheap and easy but a Poor Design Approach to use Spacer Ropes with No dielectric Spacers !
    73
    Mike
    WB6DJI

    1. Hello Mike,

      You’re absolutely spot on – This was quite early in the development of this model of Hexbeam and the design has been changed significantly. After going through a few iterations (which I managed to burn out), the designer now produces a spacer which doesn’t suffer from this.

      The recent ZL7/K5WE dxpedition to Chatham Islands took a badly designed Hexbeam and he had the same problem over and over again. From the pictures he posted, it looked as though the spacer was literally just tied to the end of the element with zero attempt at any insulation whatsoever. It’s no great surprise that he was repairing it every day.

      73 Keith

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