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RF Window Size
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? Thanks, Pat |
RF Window Size
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. -- Roger Hayter |
RF Window Size
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RF Window Size
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. -- Rick |
RF Window Size
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. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
RF Window Size
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. -- Roger Hayter |
RF Window Size
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 |
RF Window Size
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RF Window Size
On Fri, 25 Mar 2016 16:45:24 +0000, (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. Good point. (Although there is already a lot of digital hash in the area throughout HF. Some from my network and some from nearby neighbors). |
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