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Thread: Mathcbox mod

  1. #1
    Membership #: 25 Free member Award Curator KK4UTO's Avatar
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    Mathcbox mod

    So I absolutely love my end fed dipole and matchbox unun. However I had noticed that when I shook the matchbox it was rattling.
    Also the tie point for the end fed was somewhat loose and in order to tighten it up I was going to have to cut the top off since it
    was glued on. So here is what I did. I took my pocket knife and ran it around the top where it had originally seperated. In the process
    I had cut the the lip off the top so it was not going to go back on again really pretty. When I finally got the top removed the toriod
    tranformer had broken free of the bottem. It had been glued with caulking. So I tightened up the antenna connection point and mixed
    some 20 minute finishing epoxy in a small paper cup. I then poured it into the cavity of the matchbox. This will do two things. It will
    seal the connections from moisture and it will hold the connections tight so they will not come loose again. Here is a picture of the
    final product. Hope it helps someone. And yes the epoxy is not inexpensive. But I probably used less than 5 dollars worth. Maybe two
    or three Pounds. I use alot of this epoxy for potting things together permanently. This is the epoxy I use.
    Click image for larger version. 

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    Steve-KK4UTO
    QTH Frankfort, KY, USA

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    Membership #: 17 Free member 2E0CRV's Avatar
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    Re: Mathcbox mod

    Hi Steve. I built one of these from scratch following the plans on the Hawaii Club web site. These are great little units and mine will match from 80 m to 10 m with my MFJ tuner. In fact my first ever contact on 80m was made with a wire connected to my matchbox. Thanks for your post!

  4. #3
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    Re: Mathcbox mod

    Thanks for your comment. I bought the matchbox while purchasing everything else to get on HF. It was a Christmas gift. Along with an FT817nd and a Z817 autotuner. I then built another one and it is the one I use at my home QTH. It's up in a tree in my back yard. I am going to use the original matchbox in the field gathering awards from the club. I just wanted to make it a bit sturdier. A picture of my home built matchbox is below. I has no counter poise connecter but will never be used for anything hotter than 5 watts. Also the two long bolts on the pl259 side were used to bolt the pl259 in place. They were cut short later. I also poured epoxy into this one too.
    Click image for larger version. 

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    Steve-KK4UTO
    QTH Frankfort, KY, USA

  5. #4
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    Re: Mathcbox mod

    I always pot my baluns and unun with epoxy.

    I use casting resin as it's cheep and RF transparent.

    Here's a recent 1:1 balun I made for my doublet...

    Click image for larger version. 

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    And a QRO choke...

    Click image for larger version. 

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    Matt - M0LMK


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    Re: Mathcbox mod

    Hi Matt. Do you have a specific name or brand for the resin you use? This is clearly the way I should be going.

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    Re: Mathcbox mod

    This is what I use..

    Water Clear Polyester Casting Resin - Easy Composites

    1Kg will do around 6 - 8 boxes as shown above.
    Matt - M0LMK


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    2E0CRV (29th Apr 2015)

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    Re: Mathcbox mod

    Thanks Matt. I'll get some of that and give it a go.

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    Re: Mathcbox mod

    Watch the mix!

    Too much accelerator and it can get quite hot when curing so use quality boxes with thick walls.
    Matt - M0LMK


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