On Fri, 25 Mar 2016 09:37:36 -0700, Jeff Liebermann
wrote:

On Fri, 25 Mar 2016 07:48:23 -0400, Pat wrote:

I want to create an RF "window" in the shed wall. How big does it
need to be to let 2400 MHz signals pass through it?

The minimum would be a half wave slot cut through the aluminum foil.
The width will vary depending on the type of antenna and its proximity
to the slot. Unless you have a half wave dipole near the slot, it
won't work. If you're using a patch antenna or something similar,
probably a half wave by half wave square hole would be a good minimum.
Of course, bigger is better as it reduces any edge diffraction
effects.

At 2.4GHz, 1 wavelength = 12.5cm so a 6.25 cm long slot would be the
minimum.

A full
wavelength? Half wavelength? Should it be rectangular or would a
vertical slot work?

See first paragraph.

If you want to get fancy, you can cut a 1/2 wave slot in the foil, and
turn it into an antenna. It's called a "slot antenna". Watch out for
the non-obvious change in polarization. A horizontal slot antenna
produces a vertically polarized signal.
http://www.antenna-theory.com/antennas/aperture/slot.php

Opening the shed door (a full size metal door)
temporarily restores a strong signal, but I was hoping a much smaller
opening would work equally well. For aesthetic reasons, I can't
experiment by cutting various size holes.

I suggest you look into what "rickman" suggested. If there's no foil
backed insulation in the attic area, and the roof tiles are not RF
attenuators or reflectors, moving the radio to the attic should be
easy enough. You could also install a fake plastic vent pipe on the
roof, and shove the antenna or radio into the pipe. Use your
imagination.

What's the smallest hole I
can cut in the foil coated insulation and be reasonably assured it
will work?

6.25 x 6.25cm However, bigger is better and I think twice as large
would be more usable. Be sure that the radio is fairly close to the
hole.

If your unspecified radio has an external antenna connector, find a
cheap patch or panel wi-fi antenna on eBay, punch a small hole in the
wall, mount the antenna on the outside of the building, and you're
done. Something like this:
http://www.ebay.com/itm/381490123431
Note that all the gain specifications are lies.

Thank you Jeff. That is what I was looking for. Thanks to all the
others who responded as well. I went over to my local Home Depot and
found a plastic cover plate that can cover a 14x14 inch (35x35 cm)
hole in drywall. I plan to remove a piece of drywall that size and
then remove a piece of the foil covered insulation - from the inside.
That will give me a good size RF window without changing the outside
appearance of the shed at all. I will then install the plastic cover
on the inside and place the wifi module near its center. I will let
you all know how it all works out in a few days.

Thanks again for your help.
73,
Pat

Pat wrote:
On Fri, 25 Mar 2016 10:58:35 -0400, rickman wrote:

On 3/25/2016 8:50 AM, Roger Hayter wrote:
Pat wrote:

On Fri, 25 Mar 2016 12:04:11 +0000, (Roger Hayter)
wrote:

Pat wrote:

My antenna theory knowledge is a little weak so I thought you guys
might be able to help.

Background:
I have a shed about 50 feet away from my house that contains water
pumps and similar equipment that I monitor. The shed has no windows
but was built using normal stud-wall construction. I built a small
device that receives information from sensors and then reports back to
my PC via my home network. I have no way to run wires to the shed
because there is a driveway in between, so I decided to use wi-fi. The
shed had a good strong wi-fi signal inside it and everything worked
well for the last 5 years. Recently, vinyl siding was added to the
shed. The installers used foil coated styrofoam insulation under the
siding. The shed has changed from being fairly transparent to RF to
being a somewhat leaky faraday shield. The wifi module still works,
but just barely. There are lots of missed messages and any
interference from devices like the microwave oven in the house shut
down communications.

Question:
I want to create an RF "window" in the shed wall. How big does it
need to be to let 2400 MHz signals pass through it? A full
wavelength? Half wavelength? Should it be rectangular or would a
vertical slot work? Opening the shed door (a full size metal door)
temporarily restores a strong signal, but I was hoping a much smaller
opening would work equally well. For aesthetic reasons, I can't
experiment by cutting various size holes. What's the smallest hole I
can cut in the foil coated insulation and be reasonably assured it
will work?


4mm, to take the coax to an outside wifi aerial. If you can't find a
wifi unit with an aerial socket, change this to usb cable to an outside
wifi dongle. but you may then need a 12mm hole for the USB plug.

What you have suggested is my "Plan B". The wifi module I am using
does not have removable antennas and the sensor box does not have USB
capabilities. Thanks for responding. ...Pat

I would look into how to couple an external aerial to the built-in
aerial of an existing wifif module. ISTR people doing this.

Altenative, how about putting a window either in the wall towards the
wifi source, or. depending on the roofing material, in the roof which
can sometimes be done with acrylic or polycarbonater replacement roofing
elements?

There's a point. If the metal was added to the walls only, you might be
able to rise above that by placing the antenna at the highest point of
the roof. I assume that is accessible in a shed.
Not this shed. Whoever built it finished the inside with drywall on
the walls and ceiling - no access to the attic. (By the way, I expect
the signal I am getting now is via the ceiling/roof.)

Pat

Drywall is very easy to cut and patch up.

Cut an access hole in the ceiling and put the RF stuff on top of the drywall.

Put a trap door over the access hole if you want to keep it all neat.


--
Jim Pennino

On 3/25/2016 2:10 PM, Pat wrote:
On Fri, 25 Mar 2016 10:58:35 -0400, rickman wrote:

On 3/25/2016 8:50 AM, Roger Hayter wrote:
Pat wrote:

On Fri, 25 Mar 2016 12:04:11 +0000, (Roger Hayter)
wrote:

Pat wrote:

My antenna theory knowledge is a little weak so I thought you guys
might be able to help.

Background:
I have a shed about 50 feet away from my house that contains water
pumps and similar equipment that I monitor. The shed has no windows
but was built using normal stud-wall construction. I built a small
device that receives information from sensors and then reports back to
my PC via my home network. I have no way to run wires to the shed
because there is a driveway in between, so I decided to use wi-fi. The
shed had a good strong wi-fi signal inside it and everything worked
well for the last 5 years. Recently, vinyl siding was added to the
shed. The installers used foil coated styrofoam insulation under the
siding. The shed has changed from being fairly transparent to RF to
being a somewhat leaky faraday shield. The wifi module still works,
but just barely. There are lots of missed messages and any
interference from devices like the microwave oven in the house shut
down communications.

Question:
I want to create an RF "window" in the shed wall. How big does it
need to be to let 2400 MHz signals pass through it? A full
wavelength? Half wavelength? Should it be rectangular or would a
vertical slot work? Opening the shed door (a full size metal door)
temporarily restores a strong signal, but I was hoping a much smaller
opening would work equally well. For aesthetic reasons, I can't
experiment by cutting various size holes. What's the smallest hole I
can cut in the foil coated insulation and be reasonably assured it
will work?


4mm, to take the coax to an outside wifi aerial. If you can't find a
wifi unit with an aerial socket, change this to usb cable to an outside
wifi dongle. but you may then need a 12mm hole for the USB plug.

What you have suggested is my "Plan B". The wifi module I am using
does not have removable antennas and the sensor box does not have USB
capabilities. Thanks for responding. ...Pat

I would look into how to couple an external aerial to the built-in
aerial of an existing wifif module. ISTR people doing this.

Altenative, how about putting a window either in the wall towards the
wifi source, or. depending on the roofing material, in the roof which
can sometimes be done with acrylic or polycarbonater replacement roofing
elements?

There's a point. If the metal was added to the walls only, you might be
able to rise above that by placing the antenna at the highest point of
the roof. I assume that is accessible in a shed.
Not this shed. Whoever built it finished the inside with drywall on
the walls and ceiling - no access to the attic. (By the way, I expect
the signal I am getting now is via the ceiling/roof.)

I wanted to modify the lighting on my porch. The ceiling is covered
with wood. So I cut a panel and framed it with some nice wood to make
an access hatch. You can do the same thing with the drywall.

--

Rick

On 3/25/2016 12:45 PM, Roger Hayter wrote:
Sn!pe wrote:



Have you considered using HomePlug powerline ethernet such as this?
$69 for a starter kit seems quite well priced. I assume that you have
power in your shed connected to your house wiring. my setup to my own
shed over a similar distance works pretty well at ~20 Mbps.

http://www.amazon.com/ZyXEL-PLA4205k...all-plug/dp/B0
05GCSZD6


I believe that some amateurs, especially those that use HF, and more
especiallly those who listen to non-amateur band transmissions on HF,
might find that suggestion bordering on the objectionable.

Is the HomePlug setup a known offender? They might use something like
CDMA to spread the noise over the band greatly reducing any interference.

--

Rick

On 3/25/2016 2:25 PM, Pat wrote:
On Fri, 25 Mar 2016 09:37:36 -0700, Jeff Liebermann
wrote:

On Fri, 25 Mar 2016 07:48:23 -0400, Pat wrote:

I want to create an RF "window" in the shed wall. How big does it
need to be to let 2400 MHz signals pass through it?

The minimum would be a half wave slot cut through the aluminum foil.
The width will vary depending on the type of antenna and its proximity
to the slot. Unless you have a half wave dipole near the slot, it
won't work. If you're using a patch antenna or something similar,
probably a half wave by half wave square hole would be a good minimum.
Of course, bigger is better as it reduces any edge diffraction
effects.

At 2.4GHz, 1 wavelength = 12.5cm so a 6.25 cm long slot would be the
minimum.

A full
wavelength? Half wavelength? Should it be rectangular or would a
vertical slot work?

See first paragraph.

If you want to get fancy, you can cut a 1/2 wave slot in the foil, and
turn it into an antenna. It's called a "slot antenna". Watch out for
the non-obvious change in polarization. A horizontal slot antenna
produces a vertically polarized signal.
http://www.antenna-theory.com/antennas/aperture/slot.php

Opening the shed door (a full size metal door)
temporarily restores a strong signal, but I was hoping a much smaller
opening would work equally well. For aesthetic reasons, I can't
experiment by cutting various size holes.

I suggest you look into what "rickman" suggested. If there's no foil
backed insulation in the attic area, and the roof tiles are not RF
attenuators or reflectors, moving the radio to the attic should be
easy enough. You could also install a fake plastic vent pipe on the
roof, and shove the antenna or radio into the pipe. Use your
imagination.

What's the smallest hole I
can cut in the foil coated insulation and be reasonably assured it
will work?

6.25 x 6.25cm However, bigger is better and I think twice as large
would be more usable. Be sure that the radio is fairly close to the
hole.

If your unspecified radio has an external antenna connector, find a
cheap patch or panel wi-fi antenna on eBay, punch a small hole in the
wall, mount the antenna on the outside of the building, and you're
done. Something like this:
http://www.ebay.com/itm/381490123431
Note that all the gain specifications are lies.

Thank you Jeff. That is what I was looking for. Thanks to all the
others who responded as well. I went over to my local Home Depot and
found a plastic cover plate that can cover a 14x14 inch (35x35 cm)
hole in drywall. I plan to remove a piece of drywall that size and
then remove a piece of the foil covered insulation - from the inside.
That will give me a good size RF window without changing the outside
appearance of the shed at all. I will then install the plastic cover
on the inside and place the wifi module near its center. I will let
you all know how it all works out in a few days.

Before hacking out insulation, I'd try the attic approach first.

--

Rick

rickman wrote:

On 3/25/2016 12:45 PM, Roger Hayter wrote:
Sn!pe wrote:



Have you considered using HomePlug powerline ethernet such as this?
$69 for a starter kit seems quite well priced. I assume that you have
power in your shed connected to your house wiring. my setup to my own
shed over a similar distance works pretty well at ~20 Mbps.

http://www.amazon.com/ZyXEL-PLA4205k...all-plug/dp/B0
05GCSZD6


I believe that some amateurs, especially those that use HF, and more
especiallly those who listen to non-amateur band transmissions on HF,
might find that suggestion bordering on the objectionable.

Is the HomePlug setup a known offender? They might use something like
CDMA to spread the noise over the band greatly reducing any interference.

I believe they already use most of the HF band (apart from notches
around the amateur bands) for bandwidth reason. The British national
society seriously considered sueing the regulator for allowing them to
vandalise the spectrum against the previously estabisihed interference
rulels.


--

Roger Hayter

On Fri, 25 Mar 2016 14:57:29 -0400, rickman wrote:

On 3/25/2016 2:25 PM, Pat wrote:
On Fri, 25 Mar 2016 09:37:36 -0700, Jeff Liebermann
wrote:

On Fri, 25 Mar 2016 07:48:23 -0400, Pat wrote:

I want to create an RF "window" in the shed wall. How big does it
need to be to let 2400 MHz signals pass through it?

The minimum would be a half wave slot cut through the aluminum foil.
The width will vary depending on the type of antenna and its proximity
to the slot. Unless you have a half wave dipole near the slot, it
won't work. If you're using a patch antenna or something similar,
probably a half wave by half wave square hole would be a good minimum.
Of course, bigger is better as it reduces any edge diffraction
effects.

At 2.4GHz, 1 wavelength = 12.5cm so a 6.25 cm long slot would be the
minimum.

A full
wavelength? Half wavelength? Should it be rectangular or would a
vertical slot work?

See first paragraph.

If you want to get fancy, you can cut a 1/2 wave slot in the foil, and
turn it into an antenna. It's called a "slot antenna". Watch out for
the non-obvious change in polarization. A horizontal slot antenna
produces a vertically polarized signal.
http://www.antenna-theory.com/antennas/aperture/slot.php

Opening the shed door (a full size metal door)
temporarily restores a strong signal, but I was hoping a much smaller
opening would work equally well. For aesthetic reasons, I can't
experiment by cutting various size holes.

I suggest you look into what "rickman" suggested. If there's no foil
backed insulation in the attic area, and the roof tiles are not RF
attenuators or reflectors, moving the radio to the attic should be
easy enough. You could also install a fake plastic vent pipe on the
roof, and shove the antenna or radio into the pipe. Use your
imagination.

What's the smallest hole I
can cut in the foil coated insulation and be reasonably assured it
will work?

6.25 x 6.25cm However, bigger is better and I think twice as large
would be more usable. Be sure that the radio is fairly close to the
hole.

If your unspecified radio has an external antenna connector, find a
cheap patch or panel wi-fi antenna on eBay, punch a small hole in the
wall, mount the antenna on the outside of the building, and you're
done. Something like this:
http://www.ebay.com/itm/381490123431
Note that all the gain specifications are lies.

Thank you Jeff. That is what I was looking for. Thanks to all the
others who responded as well. I went over to my local Home Depot and
found a plastic cover plate that can cover a 14x14 inch (35x35 cm)
hole in drywall. I plan to remove a piece of drywall that size and
then remove a piece of the foil covered insulation - from the inside.
That will give me a good size RF window without changing the outside
appearance of the shed at all. I will then install the plastic cover
on the inside and place the wifi module near its center. I will let
you all know how it all works out in a few days.

Before hacking out insulation, I'd try the attic approach first.

Too late. I already did it and without moving the wifi module to be
near the hole, the signal already improved from marginal (a red
indicator LED) to OK (the LED is now yellow). Tomorrow, I will move
the wifi module to be near the hole. I expect a green LED after that.

Pat

On Fri, 25 Mar 2016 18:32:37 -0000, wrote:

Pat wrote:
On Fri, 25 Mar 2016 10:58:35 -0400, rickman wrote:

On 3/25/2016 8:50 AM, Roger Hayter wrote:
Pat wrote:

On Fri, 25 Mar 2016 12:04:11 +0000, (Roger Hayter)
wrote:

Pat wrote:

My antenna theory knowledge is a little weak so I thought you guys
might be able to help.

Background:
I have a shed about 50 feet away from my house that contains water
pumps and similar equipment that I monitor. The shed has no windows
but was built using normal stud-wall construction. I built a small
device that receives information from sensors and then reports back to
my PC via my home network. I have no way to run wires to the shed
because there is a driveway in between, so I decided to use wi-fi. The
shed had a good strong wi-fi signal inside it and everything worked
well for the last 5 years. Recently, vinyl siding was added to the
shed. The installers used foil coated styrofoam insulation under the
siding. The shed has changed from being fairly transparent to RF to
being a somewhat leaky faraday shield. The wifi module still works,
but just barely. There are lots of missed messages and any
interference from devices like the microwave oven in the house shut
down communications.

Question:
I want to create an RF "window" in the shed wall. How big does it
need to be to let 2400 MHz signals pass through it? A full
wavelength? Half wavelength? Should it be rectangular or would a
vertical slot work? Opening the shed door (a full size metal door)
temporarily restores a strong signal, but I was hoping a much smaller
opening would work equally well. For aesthetic reasons, I can't
experiment by cutting various size holes. What's the smallest hole I
can cut in the foil coated insulation and be reasonably assured it
will work?


4mm, to take the coax to an outside wifi aerial. If you can't find a
wifi unit with an aerial socket, change this to usb cable to an outside
wifi dongle. but you may then need a 12mm hole for the USB plug.

What you have suggested is my "Plan B". The wifi module I am using
does not have removable antennas and the sensor box does not have USB
capabilities. Thanks for responding. ...Pat

I would look into how to couple an external aerial to the built-in
aerial of an existing wifif module. ISTR people doing this.

Altenative, how about putting a window either in the wall towards the
wifi source, or. depending on the roofing material, in the roof which
can sometimes be done with acrylic or polycarbonater replacement roofing
elements?

There's a point. If the metal was added to the walls only, you might be
able to rise above that by placing the antenna at the highest point of
the roof. I assume that is accessible in a shed.
Not this shed. Whoever built it finished the inside with drywall on
the walls and ceiling - no access to the attic. (By the way, I expect
the signal I am getting now is via the ceiling/roof.)

Pat

Drywall is very easy to cut and patch up.

Cut an access hole in the ceiling and put the RF stuff on top of the drywall.

Put a trap door over the access hole if you want to keep it all neat.

The problem with that is the shed has a gable roof. The new siding
and foil backed insulation goes all the way to the peak on the ends.
Unfortunately, the wifi signal comes from one of those ends.

Pat

On Fri, 25 Mar 2016 14:54:16 -0400, rickman wrote:

On 3/25/2016 2:10 PM, Pat wrote:
On Fri, 25 Mar 2016 10:58:35 -0400, rickman wrote:

On 3/25/2016 8:50 AM, Roger Hayter wrote:
Pat wrote:

On Fri, 25 Mar 2016 12:04:11 +0000, (Roger Hayter)
wrote:

Pat wrote:

My antenna theory knowledge is a little weak so I thought you guys
might be able to help.

Background:
I have a shed about 50 feet away from my house that contains water
pumps and similar equipment that I monitor. The shed has no windows
but was built using normal stud-wall construction. I built a small
device that receives information from sensors and then reports back to
my PC via my home network. I have no way to run wires to the shed
because there is a driveway in between, so I decided to use wi-fi. The
shed had a good strong wi-fi signal inside it and everything worked
well for the last 5 years. Recently, vinyl siding was added to the
shed. The installers used foil coated styrofoam insulation under the
siding. The shed has changed from being fairly transparent to RF to
being a somewhat leaky faraday shield. The wifi module still works,
but just barely. There are lots of missed messages and any
interference from devices like the microwave oven in the house shut
down communications.

Question:
I want to create an RF "window" in the shed wall. How big does it
need to be to let 2400 MHz signals pass through it? A full
wavelength? Half wavelength? Should it be rectangular or would a
vertical slot work? Opening the shed door (a full size metal door)
temporarily restores a strong signal, but I was hoping a much smaller
opening would work equally well. For aesthetic reasons, I can't
experiment by cutting various size holes. What's the smallest hole I
can cut in the foil coated insulation and be reasonably assured it
will work?


4mm, to take the coax to an outside wifi aerial. If you can't find a
wifi unit with an aerial socket, change this to usb cable to an outside
wifi dongle. but you may then need a 12mm hole for the USB plug.

What you have suggested is my "Plan B". The wifi module I am using
does not have removable antennas and the sensor box does not have USB
capabilities. Thanks for responding. ...Pat

I would look into how to couple an external aerial to the built-in
aerial of an existing wifif module. ISTR people doing this.

Altenative, how about putting a window either in the wall towards the
wifi source, or. depending on the roofing material, in the roof which
can sometimes be done with acrylic or polycarbonater replacement roofing
elements?

There's a point. If the metal was added to the walls only, you might be
able to rise above that by placing the antenna at the highest point of
the roof. I assume that is accessible in a shed.
Not this shed. Whoever built it finished the inside with drywall on
the walls and ceiling - no access to the attic. (By the way, I expect
the signal I am getting now is via the ceiling/roof.)

I wanted to modify the lighting on my porch. The ceiling is covered
with wood. So I cut a panel and framed it with some nice wood to make
an access hatch. You can do the same thing with the drywall.

I ended up using a plastic cover plate I found at Home Depot. It is
essential what you are recommending, but instead of making it from
wood, it comes ready made. It only cost $14 USD. It has a frame that
spans to studs and a 14" x 14" removalble door insert. Not as nice as
what you propose, but for the shed, it is one of the nicest looking
things in there :-)

On 3/25/2016 5:06 PM, Pat wrote:
On Fri, 25 Mar 2016 14:54:16 -0400, rickman wrote:

On 3/25/2016 2:10 PM, Pat wrote:
On Fri, 25 Mar 2016 10:58:35 -0400, rickman wrote:

On 3/25/2016 8:50 AM, Roger Hayter wrote:
Pat wrote:

On Fri, 25 Mar 2016 12:04:11 +0000, (Roger Hayter)
wrote:

Pat wrote:

My antenna theory knowledge is a little weak so I thought you guys
might be able to help.

Background:
I have a shed about 50 feet away from my house that contains water
pumps and similar equipment that I monitor. The shed has no windows
but was built using normal stud-wall construction. I built a small
device that receives information from sensors and then reports back to
my PC via my home network. I have no way to run wires to the shed
because there is a driveway in between, so I decided to use wi-fi. The
shed had a good strong wi-fi signal inside it and everything worked
well for the last 5 years. Recently, vinyl siding was added to the
shed. The installers used foil coated styrofoam insulation under the
siding. The shed has changed from being fairly transparent to RF to
being a somewhat leaky faraday shield. The wifi module still works,
but just barely. There are lots of missed messages and any
interference from devices like the microwave oven in the house shut
down communications.

Question:
I want to create an RF "window" in the shed wall. How big does it
need to be to let 2400 MHz signals pass through it? A full
wavelength? Half wavelength? Should it be rectangular or would a
vertical slot work? Opening the shed door (a full size metal door)
temporarily restores a strong signal, but I was hoping a much smaller
opening would work equally well. For aesthetic reasons, I can't
experiment by cutting various size holes. What's the smallest hole I
can cut in the foil coated insulation and be reasonably assured it
will work?


4mm, to take the coax to an outside wifi aerial. If you can't find a
wifi unit with an aerial socket, change this to usb cable to an outside
wifi dongle. but you may then need a 12mm hole for the USB plug.

What you have suggested is my "Plan B". The wifi module I am using
does not have removable antennas and the sensor box does not have USB
capabilities. Thanks for responding. ...Pat

I would look into how to couple an external aerial to the built-in
aerial of an existing wifif module. ISTR people doing this.

Altenative, how about putting a window either in the wall towards the
wifi source, or. depending on the roofing material, in the roof which
can sometimes be done with acrylic or polycarbonater replacement roofing
elements?

There's a point. If the metal was added to the walls only, you might be
able to rise above that by placing the antenna at the highest point of
the roof. I assume that is accessible in a shed.
Not this shed. Whoever built it finished the inside with drywall on
the walls and ceiling - no access to the attic. (By the way, I expect
the signal I am getting now is via the ceiling/roof.)

I wanted to modify the lighting on my porch. The ceiling is covered
with wood. So I cut a panel and framed it with some nice wood to make
an access hatch. You can do the same thing with the drywall.

I ended up using a plastic cover plate I found at Home Depot. It is
essential what you are recommending, but instead of making it from
wood, it comes ready made. It only cost $14 USD. It has a frame that
spans to studs and a 14" x 14" removalble door insert. Not as nice as
what you propose, but for the shed, it is one of the nicest looking
things in there :-)

Mine was basically free. The wood was reused as the removable panel and
the trim wood was scrap. I think I nail the trim to the door and used a
couple of screws to hold it to the ceiling. Still $14 is not much more
than free and saves some work.

--

Rick