elektroda.net NewsGroups Forum Index - Electronics Design - what material reflects microwave?
Paul Keinanen
Guest
Guest
Mon Aug 30, 2010 7:32 am
On Sun, 29 Aug 2010 22:10:53 -0700 (PDT), "miso_at_sushi.com"
<miso_at_sushi.com> wrote:
Quote:
You might want to research passive reflectors. Not my field, but I
know they are used commercially. You find passive reflectors generally
in rural areas when they run telecom signals over microwave. Rather
than doing point to point microwave links, they put a reflector in the
middle and keep the transmitter/receiver on the ground. Damn clever of
these phone companies, since that saves them the hassle of driving up
mountain tops to repair their gear.
know they are used commercially. You find passive reflectors generally
in rural areas when they run telecom signals over microwave. Rather
than doing point to point microwave links, they put a reflector in the
middle and keep the transmitter/receiver on the ground. Damn clever of
these phone companies, since that saves them the hassle of driving up
mountain tops to repair their gear.
Passive repeaters (either simple reflectors or directional
antenna-cable-directional antenna) are useful very close to either end
of the link, but at midpoint, it is usually useless.
The power captured from the transmitter by the reflector is inversely
proportional to the square of distance. Also the power from the
reflector to final receiver is inversely proportional to he square of
the latter distance.
A reflector at the midpoint is equivalent to the situation in the
radar equation, i.e. the received power is inversely proportional to
the forth power of distance from the reflector to either end station.
Moving the reflector closer to one end and we have the bistatic radar
case.
Assuming initial condition with a total distance between end points of
60 km and a reflector at mid point and a certain very small power is
received.
Move the reflector above the receiver antenna on a mountain 3 km away.
Now the distance from transmitter to reflector is doubled and hence
path loss increases by 6 dB, but the path from reflector to receiver
drops to 1/10 and that path loss drops by 20 dB, so the signal
strength increases by 14 dB.
By putting the same reflector on a 300 m tower, the latter path loss
drops with an additional 20 dB and the received power increased by 34
dB compared to the midpoint situation.
A reflector at only 30 m (assuming free path to the reflector) would
give 54 dB stronger signals compared to the midpoint reflector.
Thus, if the signal is just usable with a reflector 30 m from the
receiver, the link will fail, if the reflector is 300-3000 m away or
even at midpoint.
Thus, in order to increase cell phone coverage e.g. in a room below
ground with a passive system, a directional antenna outside on a mast
aimed towards the cellular tower a low loss coaxial cable down into
the room below ground and an omnidirectional antenna in that room
might help.
Assuming minimal cable losses, there is one path loss from the
cellular tower to the directional antenna and an other pass loss
within the room from the omnidirectional antenna to the cell phone. Of
course the gain of the directional antenna also helps a bit. The cell
phone might be usable a few meters from the indoor antenna and there
is no need to directly connect the coaxial to the phone.
miso@sushi.com
Guest
Guest
Mon Aug 30, 2010 8:10 am
On Aug 29, 9:47 am, jgy2001 <jgy2...@gmail.com> wrote:
Quote:
If I make a flat metal sheet as antenna on window from inside my
apartment, to improve sign reception and transmission, what kind of
pattern should I use for Wifi (2.45GHz) and Cellular (GSM has 4 bands,
do not know what is best frequency for rest others?)
To: m...@sushi.com, why spray on Nickel? Is Nickel good in absorb or
reflect microwave?
apartment, to improve sign reception and transmission, what kind of
pattern should I use for Wifi (2.45GHz) and Cellular (GSM has 4 bands,
do not know what is best frequency for rest others?)
To: m...@sushi.com, why spray on Nickel? Is Nickel good in absorb or
reflect microwave?
You might want to research passive reflectors. Not my field, but I
know they are used commercially. You find passive reflectors generally
in rural areas when they run telecom signals over microwave. Rather
than doing point to point microwave links, they put a reflector in the
middle and keep the transmitter/receiver on the ground. Damn clever of
these phone companies, since that saves them the hassle of driving up
mountain tops to repair their gear.
Commercially, I've only seen Microflect.
http://www.valmont.com/page.aspx?id=91
If you live in the US and want a strong signal at home, go T-Mobile
and get one of their wifi capable phones. They call the service UMTS.
Some call it GOIP (gsm over IP). I've used the wifi phone service in
locations where there is no cellular service.
Michael A. Terrell
Guest
Guest
Mon Aug 30, 2010 9:32 am
"miso_at_sushi.com" wrote:
Quote:
You might want to research passive reflectors. Not my field, but I
know they are used commercially. You find passive reflectors generally
in rural areas when they run telecom signals over microwave. Rather
than doing point to point microwave links, they put a reflector in the
middle and keep the transmitter/receiver on the ground. Damn clever of
these phone companies, since that saves them the hassle of driving up
mountain tops to repair their gear.
You've never heard of 'Over the horizon microwave telephone relay"?
Search for 'White Alice Network' which was build in the '40s
--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.
Fred Abse
Guest
Guest
Mon Aug 30, 2010 5:02 pm
On Mon, 30 Aug 2010 12:16:21 +1000, Grant wrote:
Quote:
IN servicing the
thing I discovered inside plastic was sprayed with conductive silver paint
for RFI reduction.
thing I discovered inside plastic was sprayed with conductive silver paint
for RFI reduction.
Likely nickel.
--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)
mpm
Guest
Guest
Mon Aug 30, 2010 6:26 pm
On Aug 29, 6:04 pm, "JosephKK"<quiettechb...@yahoo.com> wrote:
Quote:
On Thu, 26 Aug 2010 12:11:53 -0700 (PDT), mpm <mpmill...@aol.com
wrote:
On Aug 26, 1:49 pm, jgy2001 <jgy2...@gmail.com> wrote:
What kind of simple material reflects microwave energy, such as
cellular and wifi signals?
I am thinking simple laminated material, such as film, or tape or
plastic sheets?
Can I embed simple film with some kind of simple metal to reflect
microwave signals?
Thank you.
The material that is embedded in some microwave popcorn bags (which is
why they always say "This Side Down".
Ditto for some microwave frozen dinner entres.
-mpm
Actually it is often more absorbtive than reflective.
wrote:
On Aug 26, 1:49 pm, jgy2001 <jgy2...@gmail.com> wrote:
What kind of simple material reflects microwave energy, such as
cellular and wifi signals?
I am thinking simple laminated material, such as film, or tape or
plastic sheets?
Can I embed simple film with some kind of simple metal to reflect
microwave signals?
Thank you.
The material that is embedded in some microwave popcorn bags (which is
why they always say "This Side Down".
Ditto for some microwave frozen dinner entres.
-mpm
Actually it is often more absorbtive than reflective.
Learn something new every day!
mpm
Guest
Guest
Mon Aug 30, 2010 6:32 pm
On Aug 29, 5:44 pm, "JosephKK"<quiettechb...@yahoo.com> wrote:
Quote:
On Thu, 26 Aug 2010 12:08:40 -0700, Tim Wescott <t...@seemywebsite.com
wrote:
On 08/26/2010 11:49 AM, jgy2001 wrote:
What kind of simple material reflects microwave energy, such as
cellular and wifi signals?
I am thinking simple laminated material, such as film, or tape or
plastic sheets?
Can I embed simple film with some kind of simple metal to reflect
microwave signals?
Metal, or just about anything that's metalized. Aluminized mylar would
certainly count as a "simple film", and is somewhat conformal if you
don't mind cussing a bit.
If you can't find it anywhere else find a hobby shop that caters to
model airplane builders and ask for metallic Monocoat, or check out the
hobby websites (Tower Hobbies is good).
You can also get aluminum backed duct tape (you _don't_ want 'regular'
silver-colored duct tape -- you want the stuff that looks like aluminum
foil).
Or you could make a form, spray 3M 77 contact cement on it, and apply
aluminum foil.
Come to think of it, even something like silver paint might -- although
if it did it'd probably scatter quite a bit.
A lot of "silver" paints contain NO metal.- Hide quoted text -
- Show quoted text -
wrote:
On 08/26/2010 11:49 AM, jgy2001 wrote:
What kind of simple material reflects microwave energy, such as
cellular and wifi signals?
I am thinking simple laminated material, such as film, or tape or
plastic sheets?
Can I embed simple film with some kind of simple metal to reflect
microwave signals?
Metal, or just about anything that's metalized. Aluminized mylar would
certainly count as a "simple film", and is somewhat conformal if you
don't mind cussing a bit.
If you can't find it anywhere else find a hobby shop that caters to
model airplane builders and ask for metallic Monocoat, or check out the
hobby websites (Tower Hobbies is good).
You can also get aluminum backed duct tape (you _don't_ want 'regular'
silver-colored duct tape -- you want the stuff that looks like aluminum
foil).
Or you could make a form, spray 3M 77 contact cement on it, and apply
aluminum foil.
Come to think of it, even something like silver paint might -- although
if it did it'd probably scatter quite a bit.
A lot of "silver" paints contain NO metal.- Hide quoted text -
- Show quoted text -
That's funny!
I was just thinking a lot of silver-plated, high-frequency RF
connectors don't contain any silver either!
I won't name them, but they hail from Belgium. Pure crap.
JosephKK
Guest
Guest
Thu Sep 02, 2010 7:02 am
On Mon, 30 Aug 2010 12:32:52 +1000, Grant <omg_at_grrr.id.au> wrote:
Quote:
On Sun, 29 Aug 2010 15:48:07 -0700, "JosephKK"<quiettechblue_at_yahoo.com> wrote:
On Fri, 27 Aug 2010 07:45:58 -0700, Tim Wescott <tim_at_seemywebsite.com
wrote:
On 08/26/2010 11:00 PM, David Eather wrote:
On 27/08/2010 7:57 AM, Tim Wescott wrote:
On 08/26/2010 02:07 PM, David Eather wrote:
On 27/08/2010 5:08 AM, Tim Wescott wrote:
On 08/26/2010 11:49 AM, jgy2001 wrote:
What kind of simple material reflects microwave energy, such as
cellular and wifi signals?
I am thinking simple laminated material, such as film, or tape or
plastic sheets?
Can I embed simple film with some kind of simple metal to reflect
microwave signals?
Metal, or just about anything that's metalized. Aluminized mylar would
certainly count as a "simple film", and is somewhat conformal if you
don't mind cussing a bit.
If you can't find it anywhere else find a hobby shop that caters to
model airplane builders and ask for metallic Monocoat, or check out the
hobby websites (Tower Hobbies is good).
The "Emergency Space Blankets" beloved by rescue and emergency services
are aluminized mylar and cost something like one or two dollars per
square yard.
Of course! Why didn't I think of that?
(please don't answer).
I have lots of time, but little money on hand.
You could make a great close-to-parabolic reflector with one of those
things just by sticking it to a round air tight frame and pulling a
vacuum. In fact, even if the frame weren't perfectly round it'd
probably still be an OK reflector.
The downside would be that you'd need to maintain the vacuum, but hey --
nothing in life is perfect.
Pretty much any air pressure differential, use the other hookup on the
household vacuum, and then spray the back with structural foam. After
it hardens you are good to go.
Frozen vacuum, sounds almost possible
Probably good enough for solar
Grant.
On Fri, 27 Aug 2010 07:45:58 -0700, Tim Wescott <tim_at_seemywebsite.com
wrote:
On 08/26/2010 11:00 PM, David Eather wrote:
On 27/08/2010 7:57 AM, Tim Wescott wrote:
On 08/26/2010 02:07 PM, David Eather wrote:
On 27/08/2010 5:08 AM, Tim Wescott wrote:
On 08/26/2010 11:49 AM, jgy2001 wrote:
What kind of simple material reflects microwave energy, such as
cellular and wifi signals?
I am thinking simple laminated material, such as film, or tape or
plastic sheets?
Can I embed simple film with some kind of simple metal to reflect
microwave signals?
Metal, or just about anything that's metalized. Aluminized mylar would
certainly count as a "simple film", and is somewhat conformal if you
don't mind cussing a bit.
If you can't find it anywhere else find a hobby shop that caters to
model airplane builders and ask for metallic Monocoat, or check out the
hobby websites (Tower Hobbies is good).
The "Emergency Space Blankets" beloved by rescue and emergency services
are aluminized mylar and cost something like one or two dollars per
square yard.
Of course! Why didn't I think of that?
(please don't answer).
I have lots of time, but little money on hand.
You could make a great close-to-parabolic reflector with one of those
things just by sticking it to a round air tight frame and pulling a
vacuum. In fact, even if the frame weren't perfectly round it'd
probably still be an OK reflector.
The downside would be that you'd need to maintain the vacuum, but hey --
nothing in life is perfect.
Pretty much any air pressure differential, use the other hookup on the
household vacuum, and then spray the back with structural foam. After
it hardens you are good to go.
Frozen vacuum, sounds almost possible
Probably good enough for solar
Grant.
Not frozen vacuum, air pressure differntial foam casting.
JosephKK
Guest
Guest
Thu Sep 02, 2010 7:04 am
On Mon, 30 Aug 2010 12:16:21 +1000, Grant <omg_at_grrr.id.au> wrote:
Quote:
On Sun, 29 Aug 2010 15:44:10 -0700, "JosephKK"<quiettechblue_at_yahoo.com> wrote:
On Thu, 26 Aug 2010 12:08:40 -0700, Tim Wescott <tim_at_seemywebsite.com
wrote:
On 08/26/2010 11:49 AM, jgy2001 wrote:
What kind of simple material reflects microwave energy, such as
cellular and wifi signals?
I am thinking simple laminated material, such as film, or tape or
plastic sheets?
Can I embed simple film with some kind of simple metal to reflect
microwave signals?
Metal, or just about anything that's metalized. Aluminized mylar would
certainly count as a "simple film", and is somewhat conformal if you
don't mind cussing a bit.
If you can't find it anywhere else find a hobby shop that caters to
model airplane builders and ask for metallic Monocoat, or check out the
hobby websites (Tower Hobbies is good).
You can also get aluminum backed duct tape (you _don't_ want 'regular'
silver-colored duct tape -- you want the stuff that looks like aluminum
foil).
Or you could make a form, spray 3M 77 contact cement on it, and apply
aluminum foil.
Come to think of it, even something like silver paint might -- although
if it did it'd probably scatter quite a bit.
A lot of "silver" paints contain NO metal.
Not even aluminium dust? But that's possibly non-conductive. The
conductive paints certainly come at a premium price.
My current lappy was given in return for data recovery, what had happened
is that it was dropped because someone tripped over the power cord. Had
been 'repaired' but was unreliable (hence the giveaway). IN servicing the
thing I discovered inside plastic was sprayed with conductive silver paint
for RFI reduction. A small piece of painted plastic had broken off and
shorted hard drive connector pins, creating havoc. Anyway, machine has
not faulted since I properly cleaned it out Some of that silver paint
does work as advertised. It's old now, made in 1999. Win98 or Win2k era.
Now crawling along with WinXP SP3.
Grant.
On Thu, 26 Aug 2010 12:08:40 -0700, Tim Wescott <tim_at_seemywebsite.com
wrote:
On 08/26/2010 11:49 AM, jgy2001 wrote:
What kind of simple material reflects microwave energy, such as
cellular and wifi signals?
I am thinking simple laminated material, such as film, or tape or
plastic sheets?
Can I embed simple film with some kind of simple metal to reflect
microwave signals?
Metal, or just about anything that's metalized. Aluminized mylar would
certainly count as a "simple film", and is somewhat conformal if you
don't mind cussing a bit.
If you can't find it anywhere else find a hobby shop that caters to
model airplane builders and ask for metallic Monocoat, or check out the
hobby websites (Tower Hobbies is good).
You can also get aluminum backed duct tape (you _don't_ want 'regular'
silver-colored duct tape -- you want the stuff that looks like aluminum
foil).
Or you could make a form, spray 3M 77 contact cement on it, and apply
aluminum foil.
Come to think of it, even something like silver paint might -- although
if it did it'd probably scatter quite a bit.
A lot of "silver" paints contain NO metal.
Not even aluminium dust? But that's possibly non-conductive. The
conductive paints certainly come at a premium price.
My current lappy was given in return for data recovery, what had happened
is that it was dropped because someone tripped over the power cord. Had
been 'repaired' but was unreliable (hence the giveaway). IN servicing the
thing I discovered inside plastic was sprayed with conductive silver paint
for RFI reduction. A small piece of painted plastic had broken off and
shorted hard drive connector pins, creating havoc. Anyway, machine has
not faulted since I properly cleaned it out
Some of that silver paint
does work as advertised. It's old now, made in 1999. Win98 or Win2k era.
Now crawling along with WinXP SP3.
Grant.
Exactly my point, some do and some don't contain metal.
Michael A. Terrell
Guest
Guest
Sat Sep 11, 2010 10:41 am
mpm wrote:
Quote:
On Aug 27, 12:25 pm, "L. Larry" <larry.py...@gmail.com> wrote:
Thank you for all your responses.
I am interested to learn the material that reflects microwave energy,
cellular and wifi signals, and these specific wavelengths?
I also interested to learn what is best and low cost to collect
cellular and wifi specific wavelength signals?
Low cost (for collecting) would be an antenna.
High cost (for reflecting) might be something like this:
Link: http://en.wikipedia.org/wiki/File:Signalreflectors.JPG
Near Salt Lake City, UT.
Up close, you can see they have little patterns cut into them to
better reflect certain wavelengths.
They use these as passive repeaters (no electronics whatsoever) to get
around mountainous terrain and other obstructions.
Sometimes you'll see them on old microwave relay towers (antennas on
the ground, passive reflector panels at altitude on a tower)
You wouldn't think they'd work, but they actually work quite well.
I recall in the early days of the space race, they launched a metal
spehere and bounced radio waves off it while it was in orbit.
Pretty much the same concept here.
-mpm
Antennas For Communications (AFC) still makes some of those microwave
antennas. The last time I passed their plant, the molds were still
sitting outside in their storage lot. They were owned by Microdyne at
one time, and made the 3 & 5 meter dishes for Microdyne's C-band CATV
and broadcast installations.
--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.
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