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Author Topic: Reuse of plastic boxes for baluns and ununs  (Read 361 times)

N8TI

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Reuse of plastic boxes for baluns and ununs
« on: April 16, 2021, 07:43:53 PM »

Hello, I just ordered an unun and a balun from ebay.  They are coming without a project box.  They cost around $14 or $15 including shipping.   When I looked at plastic boxes, they were all $12 or more with shipping.  It  bothers me to pay more for the box as the unun, as at that point, I could have just bought one all put together in a box, had I known. (I know, that is why the ones without the box are cheaper.) So, looking for something, I saw my wife had just thrown out an squarish Arm and Hammer disinfectant wipes box that has a little door that is waterproof, (as it has to prevent the wet wipes from drying out),  and can be cut down and taped back together and will make a nice balun and unun box.  Any other ideas? 
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WB6BYU

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Re: Reuse of plastic boxes for baluns and ununs
« Reply #1 on: April 16, 2021, 08:25:28 PM »

Rummaging around at the local Goodwill store
has turned up a number of useful boxes for
baluns, tuners, etc., of the type with snap-on
lids, but more sturdy than traditional Tupperware.
I think these are designed for use in lunch boxes.

My favorite had “Dora the Explorer” on it.

K6AER

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Re: Reuse of plastic boxes for baluns and ununs
« Reply #2 on: April 16, 2021, 08:29:42 PM »

You can buy a nice plastic utility box in the electrical section at Home depot for $8.00. I use these when building a 2 KW 9:1 Unun's.
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KL7CW

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Re: Reuse of plastic boxes for baluns and ununs
« Reply #3 on: April 16, 2021, 08:43:26 PM »

I often use electrical (PVC) boxes from the big box stores.  I have used them for relays, baluns, matching networks, loading coils and common mode chokes.  I like the Carlon ones and often use just the box without ports and use brass hardware to enter and exit the boxes, or often just glue a coupling to the bottom of the box, run a hole saw through the coupling and run my ethernet or coax cables up through the bottom.  In one situation I glued 3 (probably one inch couplings) to the bottom of a 4 x 4 x 4 box and many RG-45 connected cables through these bottom openings stuffed with fiberglass.  I have also put electronics inside a short piece of PVC tube with endcaps and used brass hardware to enter and exit the tube.  These boxes are inexpensive, but in some situations may weigh more than you want at the center of a dipole.  It is very difficult (impossible ?) to completely weather seal any enclosure, that is why I always try and bring all cables into the bottom and use a very small weep hole as a drain. 
       My method is not the only way to do things, so do what works for you.  In one situation I even put a 90 degree plumbing elbow in the side of a box and brought my coax up that way....never any moisture problems, and the RF exited the box in other areas away from the elbow via brass bolts and nuts.              Rick   KL7CW
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W4MDP

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Re: Reuse of plastic boxes for baluns and ununs
« Reply #4 on: April 16, 2021, 11:31:21 PM »

treIf you have a Dollar Store or a Dollar General take a look around them.  I have oftem found plastic boxes with ssnq on lids for antenna tuners and such.  They are watertight.
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W9WQA

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Re: Reuse of plastic boxes for baluns and ununs
« Reply #5 on: April 17, 2021, 08:45:41 AM »

or pvc plumbing pipe
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KL7CW

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Re: Reuse of plastic boxes for baluns and ununs
« Reply #6 on: April 17, 2021, 11:35:46 AM »

Up here in Alaska where the UV index is usually low or zero, misc. "plastic" kitchen containers may last a few years, but for permanent use I go with quality boxes.  Many options in the electrical sections of box or other stores which last many decades.  "Kitchen" boxes, etc. probably would not even last a few years in most areas.  Many electrical options for less than $10.
    I like to walk around the electrical, plumbing, gardening section, and hardware section of box and hardware stores.  Even pet stores had some items, like screw in pet anchors for temporary antenna guy wires.         Happy shopping,  KL7CW
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WD4HXG

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Re: Reuse of plastic boxes for baluns and ununs
« Reply #7 on: April 17, 2021, 04:12:30 PM »

While it is annoying to have to pay what seems to be an
outlandish price for an enclosure, if you want long service
life you need to look for boxes that will survive the harsh
environment of sun, moisture and temperature extremes.
A box may look pretty and seem durable but UV can
degrade many plastics rapidly. Plastic degradation can open
paths for moisture ingress and your prized device can be
turned into junk while you are inside thinking all is well in
the protective enclosure.

While I like to save a few bucks while shopping, the first goal
is to find a box which has attributes that will make it a long
term solution that does not require me lowering it every 30
days for inspection. Food storage containers for home rarely
satisfy my need for such projects. To that end Carlon electrical
boxes are one of my go solutions. They have a nearly ubiquitous
6" X 6" X 4" thick walled box that is durable and lasts for years
in the outdoors in eastern North Carolina. The box is provided
with a O-Ring type seal for the cover. If I bore holes in the box
for pass throughs such as eyebolts, the holes are bored with a
numbered drill to create a hole just large enough for the eyebolt
to slip through. Hardware on the inside and outside includes a
wide flat washer on each surface. Non-acetic acid RTV is used to
form seals around hardware passing through any bored holes.
Even with that I drop the box and inspect the seal points at least
once a year. Mold and water are insidious and seemingly can
breach just about any gasketed/sealed access.

Another protective feature you can use is a product known as MFP
(Moisture Fungus Proofing). It is a liquid protective coating, that
you dip the device into and allow it to cure before installing the
device in the protective enclosure. The original MFP came into vogue
during WWII when the military needed to protect vulnerable
electronics. Even today when you open WWII surplus equipment you
find the original MFP still in place with its characteristic sort of phenol
odor. Even if water does ingress your box, often the MFP blocks its
destructive effects. Many WWII radios were coated on the interior to
include solder joints. Those joints look pristine nearly over 75 plus
years later. It is tough stuff.

In more demanding applications I will include a sensor to monitor
humidity. It is fairly easy these days given all the stuff showing up for
integration with microprocessors. A relatively short Python script
running on your micro can alert you if the moisture level in the
enclosure rises above the status quo and give you early warning of the
need to check things upstairs.

Carlon is by no means the only purveyor of electrical boxes that can
be used in demanding locations, they simply are the popular brand
that is readily available in the  big box home improvement stores.
Unfortunately the subset of durability, quality, availability and low cost
is a very small spot on the set chart and almost universally cost is the
sacrificial lamb when relaxing requirements if one insists on holding the
line with other attributes.

YMMV

73

Chuck
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AC9QC

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Re: Reuse of plastic boxes for baluns and ununs
« Reply #8 on: May 31, 2021, 06:31:53 AM »

If you have any one that can do it for you 3D printing is a wonder of the world. There's a decent amount of ham radio stuff on Thingiverse I'd check there perhaps make something.
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