Thanks for your reply, Bob...

Unfortunately, the window is not feasible, but the coax approach
should work. MOunting to a small board or knockout might be a good
idea, so I could save the cut-out materials and be able to un-do the
hatchet work if that was ever necessary.

Thanks for your reply.
73
Dan (K0DAN)

On Wed, 16 Feb 2005 14:36:17 GMT, Bob Miller
wrote:

On Tue, 15 Feb 2005 21:44:34 -0600, me wrote:

After many years of experimenting with coax fed wire antennas I am
taking my first plunge at open wire line.

To get into shack, I need to go through exterior steel siding,
exterior wood siding & plywood, a layer of insulation, then interior
sheetrock and wood paneling. Assume I need about 4-6" of safe
feedthrough so that standoffs can be mounted on the walls oustide
and inside the shack.

I generally run 100 to 1500W output...at full legal limit probably
3KV on the feedline...am not crazy about the idea of setting my house
on fire due to HV arc over.

Am looking for the old style porcelain feedthrough isnulators, but so
far have not found same.

Local Home Depot has thin PVC tubing (as in sink/toilet stems), vinyl
tubing, welding rod tubes, etc. What are the dielectric properties of
these, and the high voltage breakdown voltage...???

Seems like glass, porcelain, or ceramic tubing would be best
feedthrough insulator, but where to find?

I use ceramic feedthrough insulators on a piece of board in the bottom
of my window to bring 450-ohm line indoors. I got the insulators from
Surplus Sales of Nebraska -- you can check their web site for info;
they have a pretty good selection of NOS in all sizes, tho' they ain't
cheap.

You may do just as well rigging something else, as per some of the
other suggestions here...

bob
k5qwg


Are any modern day materials found in Lowes or Home Depot safe from
arcing and also efficient for RF?

Thanks in davance & 73,

Dan (K0DAN)

Dan,
Have a window fairly close to your transmitter/tuner? Replace
the glass with plexiglass, or drill a couple of holes in the glass,
or make a 'spacer' to fit in the window opening.
How about through the eaves, to attic, through ceiling?
'Doc

On Wed, 16 Feb 2005 09:31:54 -0600, me wrote:

Excellent idea...I can envision a couple N or UHF connectors on either
side of the wall, and the entry point is indeed near the ground system
so that too is feasible. Thanks for the tip...there are others coming
in but this sounds very feasible and relatively easy!

No, sorry, that is not what I had in mind and should have cleared that
up right at the outset.

I never use coax connectors in this situation, although I suppose you
could. I simply connect balanced line to the innter conductors of the
coax's on each side of the balanced coax segment. If you want a quick
disconnect, I use a pair of the General Radio type Banana plugs just
inside the shack. They are convenient for several reasons.
1) they seem to be able to stand the power level.

2) the spacing on the wire connectors is exactly right for 450 ohm
window line, and

3)they are hermaphroditic - i.e., they plug into one another either
way.


Bob, W9DMK, Dahlgren, VA
Replace "nobody" with my callsign for e-mail
http://www.qsl.net/w9dmk
http://zaffora/f2o.org/W9DMK/W9dmk.html

Hi Doc...

There is an awning type window, however penetrating or replacing it is
not feasible. In this particular part of the house, eaves & attic are
not accessible and don't route to the hamshack.

However today I discovered two parallel runs of 1/2" Heliax which I
installed in the late 70's and which have been abandoned and
forgotten. These already exit up the hamshack wall, through the sole
plate just above ground level, and route over the deck and underground
to the location of a former tower. They can easily be cut off, and
their center conductors used as the feed through...once cut I believe
total length would be perhaps 6 to 10 feet; not ideal but would not
require any new construction.

The planned open wire line will be 600 ohm type with about 5"
spacing...need to figure a way to use banana plugs, gator clips or
something like that to make the transition from wire to the center
copper of the Heliaz...maybe solder some copper tubing over the Heliax
center? A trip to the hardware store is in order.

Thanks and 73

Dan (K0DAN)

On Wed, 16 Feb 2005 15:56:28 GMT, 'Doc wrote:

Dan,
Have a window fairly close to your transmitter/tuner? Replace
the glass with plexiglass, or drill a couple of holes in the glass,
or make a 'spacer' to fit in the window opening.
How about through the eaves, to attic, through ceiling?
'Doc

Here's my method to make a neat through the wall twin lead or OWL
feedthrough:
Materials: 3/4 inch or larger PVC pipe, 2 PVC end caps preferably with
flat ends,
2 lengths of 6-32 threaded brass rod (McMaster Carr) or True Value,
6-32 nuts and washers, RTV.
Cut the PVC pipe = the wall thickness + about 1 inch.
Drill and tap one end cap for the rods and drill 6-32 clearance holes
in the other cap. I used about 5/8 inch spacing.
Cut the rods about 2 or 3 in. longer than the pipe.
Drill a pilot hole from the inside wall through the outside with a long
masonry drill (use a stud finder to miss the studs). Use a 1 inch
spade style wood bit to bore a hole first through the inside wall and
then through the outside stucco. I was surprised at how well the wood
bit worked.
The rest of the story is pretty obvious. I'd use RTV rather than PVC
cement so that the assembly can later be pulled apart if necessary.
73, John, KU6X

That's a really nice approach. I just discovered a pair of 1/2" Heliax
feedlines already thru my wall...abandoned many years ago. If these
fail to work due to impedance mismatch or other as yet unknown
problems, I will try your brass rod in PVC approach...or one of the
several coax thru the wall methods. So many answers, so little time!
73
Dan K0DAN


On 16 Feb 2005 20:14:01 -0800, "KU6X" wrote:

Here's my method to make a neat through the wall twin lead or OWL
feedthrough:
Materials: 3/4 inch or larger PVC pipe, 2 PVC end caps preferably with
flat ends,
2 lengths of 6-32 threaded brass rod (McMaster Carr) or True Value,
6-32 nuts and washers, RTV.
Cut the PVC pipe = the wall thickness + about 1 inch.
Drill and tap one end cap for the rods and drill 6-32 clearance holes
in the other cap. I used about 5/8 inch spacing.
Cut the rods about 2 or 3 in. longer than the pipe.
Drill a pilot hole from the inside wall through the outside with a long
masonry drill (use a stud finder to miss the studs). Use a 1 inch
spade style wood bit to bore a hole first through the inside wall and
then through the outside stucco. I was surprised at how well the wood
bit worked.
The rest of the story is pretty obvious. I'd use RTV rather than PVC
cement so that the assembly can later be pulled apart if necessary.
73, John, KU6X

Hi.
I recently completed just what you are planning to do. I got 2 NOS feed
throughs last year on Ebay. They each consisted of a threaded rod with
nuts and washers, two cone shaped insulators and more than enough
ceramic cylinders, for the rod, to pass through my wall. I had to cut
new cork gaskets to go under the insulators. The old ones just fell
apart.

I had to construct a similar feed through for the connection to the
ground just outside my shack. Here I used a threaded rod, two 1/4 in.
plastic disks, and a plastic tube cut to length for the wall feed
through.

If you are anywhere near a plastic supplier, such at TAP plastic, they
will have all the stuff you need.

Good luck.

Paul, KD7HB