Potting a balun: wax vs. epoxy vs. urethane foam?
 

I have a low-power 4:1 toroid balun almost ready in a little plastic
box. In order to keep the rain out, I am sealing everything up, but I
am also considering space-filling materials.

I am leaning toward filling it with hot "wax" - actually, paraffin
from standard household candles, although a harder grade like
sometimes found in old military equipment should be better.

The pro should be that the box would not become sealed for eternity in
case I want to re-wire something in the future, while epoxy is bomb
proof, and urethane foam is also rather hard to remove.

Is there any electrical con to be considered?

On 16 Aug 2004 11:11:54 -0700, (SpamHog) wrote:

I have a low-power 4:1 toroid balun almost ready in a little plastic
box. In order to keep the rain out, ...

Is there any electrical con to be considered?

Hi OM,

It increases the input to output capacity (reduces isolation).

Use the lid to keep the rain out. Invest your time in its seal.

If you want a hard, hard wax, visit a dental supplier, or a nearby
laboratory. They use very hard waxes for investment molds. Or they
used to....

73's
Richard Clark, KB7QHC

I used 3m 'Scotchkote' to coat the whole shebang - it waterproofs it ok
you can get it in the electrical section of Home Depot or Lowes, etc.
but both your suggestions sounds good - Silicone would be my chouce of the
2.
other things to try : 3M 'Scotchfil' (its like a rubber putty) then cover
with 3M 88 weatherproof tape.
and of course - we can't forget epoxy (but it will crack in time)

"SpamHog" wrote in message
om...
I have a low-power 4:1 toroid balun almost ready in a little plastic
box. In order to keep the rain out, I am sealing everything up, but I
am also considering space-filling materials.

I am leaning toward filling it with hot "wax" - actually, paraffin
from standard household candles, although a harder grade like
sometimes found in old military equipment should be better.

The pro should be that the box would not become sealed for eternity in
case I want to re-wire something in the future, while epoxy is bomb
proof, and urethane foam is also rather hard to remove.

Is there any electrical con to be considered?


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On Mon, 16 Aug 2004 18:50:58 GMT, Richard Clark wrote:

If you want a hard, hard wax, visit a dental supplier, or a nearby
laboratory. They use very hard waxes for investment molds. Or they
used to....


Or maybe a production machine shop. They frequently use a nice hard
wax to proof CNC programs...

--
-fb-

"Richard Clark" wrote in message
...
On 16 Aug 2004 11:11:54 -0700, (SpamHog) wrote:

I have a low-power 4:1 toroid balun almost ready in a little plastic
box. In order to keep the rain out, ...

Is there any electrical con to be considered?

Hi OM,

It increases the input to output capacity (reduces isolation).

Use the lid to keep the rain out. Invest your time in its seal.

If you want a hard, hard wax, visit a dental supplier, or a nearby
laboratory. They use very hard waxes for investment molds. Or they
used to....

73's
Richard Clark, KB7QHC

It is almost impossible to keep all moisture out. This will condense when
the temperature drops. Drill some very small drain holes in the bottom
(after you have sealed it the best you can).

Tam/WB2TT

Thank you all!

Here's what I intend to do:


- coat everything internally,
but without a space-filler


- seals

* fixed, for plugs and tieposts: a locally made silicone based strong
adhesive/sealant + external soft silicone coat

* reopenable, for the box lid: just soft silicone sealant

* wire tieposts & coax plug:
- soft silicone sealant, left to dry completely
- then wrapped in aluminum foil (no metal contact)
- then wrapped in friction tape, held in place by telephone twisted
pair;
it's another suspenders-and-belt trick I have used this to
weatherproof all sorts of antenna contacts, some lasting well over 10
years


This for keeping water out,
But, in case it does somehow get in, what about WEEP HOLES?

Thank you all!

Here's what I intend to do:


- coat everything internally,
but without a space-filler


- seals

* fixed, for plugs and tieposts: a locally made silicone based strong
adhesive/sealant + external soft silicone coat

* reopenable, for the box lid: just soft silicone sealant

* wire tieposts & coax plug:
- soft silicone sealant, left to dry completely
- then wrapped in aluminum foil (no metal contact)
- then wrapped in friction tape, held in place by telephone twisted
pair;
it's another suspenders-and-belt trick I have used this to
weatherproof all sorts of antenna contacts, some lasting well over 10
years


This for keeping water out,
But, in case it does somehow get in, what about WEEP HOLES?

Thank you all!

Here's what I intend to do:


- coat everything internally,
but without a space-filler


- seals

* fixed, for plugs and tieposts: a locally made silicone based strong
adhesive/sealant + external soft silicone coat

* reopenable, for the box lid: just soft silicone sealant

* wire tieposts & coax plug:
- soft silicone sealant, left to dry completely
- then wrapped in aluminum foil (no metal contact)
- then wrapped in friction tape, held in place by telephone twisted
pair;
it's another suspenders-and-belt trick I have used this to
weatherproof all sorts of antenna contacts, some lasting well over 10
years


This for keeping water out,
But, in case it does somehow get in, what about WEEP HOLES?

Thank you all!

Here's what I intend to do:


- coat everything internally,
but without a space-filler


- seals

* fixed, for plugs and tieposts: a locally made silicone based strong
adhesive/sealant + external soft silicone coat

* reopenable, for the box lid: just soft silicone sealant

* wire tieposts & coax plug:
- soft silicone sealant, left to dry completely
- then wrapped in aluminum foil (no metal contact)
- then wrapped in friction tape, held in place by telephone twisted
pair;
it's another suspenders-and-belt trick I have used this to
weatherproof all sorts of antenna contacts, some lasting well over 10
years


This for keeping water out,
But, in case it does somehow get in, what about WEEP HOLES?

Thank you all!

Here's what I intend to do:


- coat everything internally,
but without a space-filler


- seals

* fixed, for plugs and tieposts: a locally made silicone based strong
adhesive/sealant + external soft silicone coat

* reopenable, for the box lid: just soft silicone sealant

* wire tieposts & coax plug:
- soft silicone sealant, left to dry completely
- then wrapped in aluminum foil (no metal contact)
- then wrapped in friction tape, held in place by telephone twisted
pair;
it's another suspenders-and-belt trick I have used this to
weatherproof all sorts of antenna contacts, some lasting well over 10
years


This for keeping water out,
But, in case it does somehow get in, what about WEEP HOLES?