The CATFISH thread - external antenna choice and use.

Post new topic   This topic is locked: you cannot edit posts or make replies.    DD-WRT Forum Index -> Broadcom SoC based Hardware
Goto page Previous  1, 2, 3, 4, 5, 6, 7, 8  Next
Author Message
Murrkf
DD-WRT Guru


Joined: 22 Sep 2008
Posts: 12675

PostPosted: Tue Jul 21, 2009 15:31    Post subject: Reply with quote
naiku wrote:
Could I angle the panel antenna upwards slightly to account for this?

The antenna in the link above says it has a 35 degree beam width, is that 35 horizontal? or vertical? or both? Thanks.


Yes. The antenna doesn't care or know where earth is or what angle from the ground it is set at. Wink Just knows what direction it is facing.

35 is normally the width and is a factor in how precise you have to be in aiming it.

I am sure that this will work fine if you have line of sight. Make sure to use low-loss coax to connect to the basement router.

_________________
SIG:
I'm trying to teach you to fish, not give you a fish. If you just want a fish, wait for a fisherman who hands them out. I'm more of a fishing instructor.
LOM: "If you show that you have not bothered to read the forum announcements or to follow the advices in them then the level of help available for you will drop substantially, also known as Murrkf's law.."
Sponsor
naiku
DD-WRT User


Joined: 25 Feb 2008
Posts: 51

PostPosted: Tue Jul 21, 2009 15:52    Post subject: Reply with quote
Murrkf wrote:

I am sure that this will work fine if you have line of sight. Make sure to use low-loss coax to connect to the basement router.


Line of sight should be pretty simple there is nothing between the houses. If I were to put this antenna in the basement, would I be basically wasting my money on it? I figure if I installed it inside, then I would only need a short coax run from the router to the antenna, saving on some of the loss there. The 2nd router is inside the house, and has no option for an external antenna (WRT310N). Just wondering if I would need to install the panel antenna outside.
Murrkf
DD-WRT Guru


Joined: 22 Sep 2008
Posts: 12675

PostPosted: Tue Jul 21, 2009 16:01    Post subject: Reply with quote
naiku wrote:
If I were to put this antenna in the basement, would I be basically wasting my money on it?


Yes.

You do want line of sight. Putting the second router in a window will help a lot though, but not enough to deal with trying to access an antenna in a basement 500 feet away.

Antennas don't create more powerful signals to get out of basements and through concrete. Better antennas are more sensitive, but there still has to be something reaching them. The signal is not going to go through concrete very well.

Use low loss coax to put the panel outside and towards the second house. (I wouldn't worry about the coax loss compared to the attenuation loss of the router being in a basement!) Put the router in the second house in a window facing the first house if you can.

_________________
SIG:
I'm trying to teach you to fish, not give you a fish. If you just want a fish, wait for a fisherman who hands them out. I'm more of a fishing instructor.
LOM: "If you show that you have not bothered to read the forum announcements or to follow the advices in them then the level of help available for you will drop substantially, also known as Murrkf's law.."
naiku
DD-WRT User


Joined: 25 Feb 2008
Posts: 51

PostPosted: Tue Jul 21, 2009 17:14    Post subject: Reply with quote
Thought putting it inside would negate most of the benefits... what happens to clients inside the first house who want wireless access now if the antenna is now located outside and pointing at another location? I also have no windows on the side of the second house that face the first house, so no chance of putting the second router in a window.
Murrkf
DD-WRT Guru


Joined: 22 Sep 2008
Posts: 12675

PostPosted: Tue Jul 21, 2009 18:23    Post subject: Reply with quote
If the router has two antennas, put them to auto. The router will take care of the traffic...external antenna for the bridge, and internal antenna for the lan inside the house. Plus, there will be a node facing backwards from the external antenna.

If the system you have is working now with a second router at the first house, it should also work well without it, in spite of the lack of window access.

_________________
SIG:
I'm trying to teach you to fish, not give you a fish. If you just want a fish, wait for a fisherman who hands them out. I'm more of a fishing instructor.
LOM: "If you show that you have not bothered to read the forum announcements or to follow the advices in them then the level of help available for you will drop substantially, also known as Murrkf's law.."
giant22000
DD-WRT User


Joined: 25 Nov 2007
Posts: 80

PostPosted: Tue Jul 21, 2009 18:49    Post subject: Reply with quote
KeithB wrote:
Nice looking antenna, good price, and you can count on FABcorp for quality products. How long a cable run will you need from your router to the antenna? Many people relocate the router outdoors onto the pole (in a sealed enclosure) to maintain as short a cable run as possible. Power over ethernet (POE) provides power to the exterior router and encounters less voltage drop over distance than RF signals do.


I would have a 15ft. cable run maximum (lmr-400). I've been debating whether or not to relocate the router outdoors using PoE to power router. I have a whr-hp-g54 and have read that the linksys 5v PoE that's used for VoIP will work fine. But, I'm trying to figure out if this will be cost effective. By the time I purchase outdoor enclosure, Linksys 5v PoE small amount of low loss coax, I would have spent nearly double of the original cost. Plus the enviroment I live in, temperatures can reach 100+ F to as low as the mid 20's F. So, not sure if the whr-hp-g54 can handle the extreme weather changes of the season. Not to mention humidity averages 90% plus all year.
Radioman193
DD-WRT User


Joined: 16 Aug 2007
Posts: 489
Location: New York

PostPosted: Tue Jul 21, 2009 20:50    Post subject: Reply with quote
Murrkf wrote:
naiku wrote:
Could I angle the panel antenna upwards slightly to account for this?

The antenna in the link above says it has a 35 degree beam width, is that 35 horizontal? or vertical? or both? Thanks.


Yes. The antenna doesn't care or know where earth is or what angle from the ground it is set at. Wink Just knows what direction it is facing.

35 is normally the width and is a factor in how precise you have to be in aiming it.

I am sure that this will work fine if you have line of sight. Make sure to use low-loss coax to connect to the basement router.


just a question to ya: Smile
If this was true then how would the
Radiation pattern will vary with height? Wink

the earths Ground is a BIG factor in your antenna system.

You can find ALOT of information on this in PDF format all over the internet.

the simple rule is that for a horizontal antenna the higher the
better for DX. You need to get the radiating bit as far away from lossy
earth as possible.

Same applies to VHF horizontal antennas, but for other reasons too.

Radiation pattern will vary with height - generally if you are less than
a half wave above ground most of your radiation will be at high angles.
That gives a shorter distance between ionospheric reflections, so your
signal doesn't go as far. Each hop incurs loss significant loss, so if
there are more of them the signal will be weaker.

To work lots of DX your horizontal antenna needs to be at least half a
wavelength up for the necessary low angle radiation to occur properly.
At lower heights there will still be low angle radiation, but much
weaker. That's why you can work DX with a low slung wire, but if the
wire were higher the signals would be stronger.

However it's all change on sloping ground. Then there is an optimum
height when ground relection can actually augment your signal quite
considerably.

For NVIS you need a horizontal antenna close to the ground, because you
want high angle radiation instead of low angle.

None of this applies to vertical antennas which work against ground.
Then earth conductivity comes to the fore.

You might want to have a play with Eznec, the demo is free at
http://www.eznec.com/demoinfo.htm It will show you graphically how this
all works
Cool

_________________
You can find me Here:
http://www.facebook.com/#!/profile.php?id=100001843308666
robert-e
DD-WRT User


Joined: 19 Feb 2007
Posts: 227

PostPosted: Wed Jul 22, 2009 3:45    Post subject: Reply with quote
Radioman193,
You are correct that the hieght above ground is important, but that is only true when the hieght is in the same order of magnitude as the wavelength. So your ideas apply to hf frequencies. However, the wavelength at 3 gHz is so small, that the ground effects would only be significant if the router were placed on the ground surface. Anything higher than a foot or so would make the router antenna act as a free-space antenna, and thus the ground effect is insignificant. Of much more importance is the Freznel Effect, and at almost any reasonable hieght raising (or lowering) the router antenna can make a difference of up to 20 dB, even if the two router/access points are line of sight.
Regards,
Bob
Radioman193
DD-WRT User


Joined: 16 Aug 2007
Posts: 489
Location: New York

PostPosted: Wed Jul 22, 2009 6:44    Post subject: Reply with quote
Radio waves travel in straight lines, but when they hit an object whose dimensions are much
larger than their wavelength, they reflect.

ALL Radio waves.

thats why you can recive a 2+ghz signal into a place you Normaly cant By "reflecting" it to the place you need Just like setting up a satellite Dish if you were to take the LMB off the dish and point it at a car roor at the Proper angle you can pick up the satellite.

2.4Ghz is Even more effected by ground than lower frequencies .
lower frequencies like in VHF will pass through an object better than High frequencies that will just bounce off them.

2.4Ghz will cut down even by a piece of glass "Window" but yet you can use that SAME piece of glass to aim or reflect that same 2.4Ghz frequencie.

If it was not for the Earths ground and magnetic field influence you would not be able to use your directional antenna you signal would not go in a strait line it would just go off all directions away from the reflecting element.

the earths ground is what Helps to give you that nice elongated pattern you get with directional antennas.


2.4GHz band
The signal bounces off buildings and almost any hard object. The path-loss is
three-times that of 900MHz and 20 times that of a VHF system, so this band is
used primarily for short-range high-speed data links such as wireless LAN. The
band has considerable noise from cordless phones and micro-wave ovens,
although the interference is often negligible as the propagation is shorter than
lower-frequencies. The range is less than UHF and there is much more absorption
by foliage.

http://www.l-com.com/multimedia/catalog_page/2K9M1_005%20HyperLink%20Brand%20Wireless%20Antennas.pdf

http://www.sputnik.com/docs/rf_propagation_basics.pdf

http://www.softwright.com/tap6.html


http://www.zerobeat.net/r3403c.pdf


Cool

_________________
You can find me Here:
http://www.facebook.com/#!/profile.php?id=100001843308666


Last edited by Radioman193 on Wed Jul 22, 2009 22:54; edited 2 times in total
robert-e
DD-WRT User


Joined: 19 Feb 2007
Posts: 227

PostPosted: Wed Jul 22, 2009 20:55    Post subject: Reply with quote
Quote

If it was not for the Earths ground influence you would not be able to use your directional antenna you signal would not go in a strait line it would just go off all directions away from the reflecting element.

the earths ground is what Helps gives you that nice elongated pattern you get with directional antennas.

Unquote

This statement is very mixed up: The earth's ground IS NOT responsible for antenna gain. Antenna gain is derived from concentrating the "waves" in a prefered direction at the expense of some other direction(s). This can best be understood by considering "constructive / distructive interference" of these wave, perhaps by applying vector analysis of the electric or magnetic field strenths, as is done in EZNEC. The reflecting element that you refer to does not have to be at ground potential, but can be so if it is 1/4 wavelength from the radiating element. Note that this term "ground" has nothing to do with the term "earth ground", that you refer to in your discussion of larger wavelength wave.

I would again assert that the hieght of a router antenna (providing it is more than a foot high) above the (earth) ground, has no appreciable effect on the gain properties of the router.

Furthermore, the absorptive (attenuation) properties of the medium the waves pass through, or reflect, have no effect on the relative gain, but only serve to attenuate the strength of those waves.

I would again reiterate: at the frequencies used by routers, the Freznel Effect is of much greater importance than the properties of the (earth) ground.

Regards,
Bob
Radioman193
DD-WRT User


Joined: 16 Aug 2007
Posts: 489
Location: New York

PostPosted: Wed Jul 22, 2009 21:21    Post subject: Reply with quote
i never sed it will affect the Gain.

the post was on
how the Earths ground and "magnetic field "will affect the signal pattern of the transmitting antenna regardless to the transmitted frequency.

Cool

_________________
You can find me Here:
http://www.facebook.com/#!/profile.php?id=100001843308666
robert-e
DD-WRT User


Joined: 19 Feb 2007
Posts: 227

PostPosted: Wed Jul 22, 2009 22:15    Post subject: Reply with quote
Actually, you did: That which you refer to as "signal pattern" is just a visual representation of the antenna's gain. To convince yourself of this. load up EZNEC and any antenna file, choose "View far-field .... ", Inspect the numbers on the pattern (in dBi or dBd). Those represent the GAIN in that direction.

Anyways, I am finished here. Someone else can continue this if they are so inclined.

Regards,
Bob
Radioman193
DD-WRT User


Joined: 16 Aug 2007
Posts: 489
Location: New York

PostPosted: Wed Jul 22, 2009 23:53    Post subject: Reply with quote
15
component known as ground resistance or ground impedance. The presence of this component
changes how RF energy is delivered to the antenna in that some energy normally radiated by the
antenna is now dissipated in the earth. This characteristic is described by the following equation
that describes the total antenna resistanceThe Effects of Earth and Other Surrounding Objects
Most, if not all antenna performance characteristics are specified under free space
conditions. It is important to realize that these performance characteristics may change once the
antenna is located in its operating environment. Surrounding objects, such as the earth, walls,
buildings, floors, etc. will impact the antenna’s specified performance. The fact that antenna
performance may change in the operating environment does not invalidate the use of free space
data. It is impossible to specify performance for all environments and the free space
performance characteristics provide the most suitable reference for comparing antenna
performance.
Rather than discussing how the earth or other surrounding objects attenuate, reflect and
diffract RF radiation (multipath), this section will briefly describe the significant ways in which
the earth directly affects antenna performance. The earth is used as the principle example for
discussion, however, the same concepts can be applied to other surrounding objects such as walls
and buildings.
Aside from contributing directly to antenna noise temperature (interference), the presence
of the earth affects an antenna’s radiation pattern and impedance characteristics. The earth acts
as a dielectric body with varying conductivity (s) and dielectric constant (er). Although values of
conductivity and dielectric constant vary with frequency and conditions over the earth’s surface,
typical values for s and er are 12 x 10-3
mho/m and 15, respectively.
When an antenna is located near the earth, its radiated field couples with the earth and
changes. The antenna impedance is changed from its free space value by the addition of a

More Here:

http://www.qsl.net/n9zia/wireless/pdf/best_doc.pdf

and ARRL has ALOT to say about this to.
Here:
http://www.arrl.org/

Earhs ground and Ground is the FIRST Basic factor of an antenna design and setup.

after Years of building Antennas beam and onmi's
for alot of different bands
11 meter
10 meter
20 meter
40 meter
and 80 meter

up to 50' long 80dbi beams "like" the Maco laser 500 but better gain and then "Stack" them.

i know a thing or 2 about antenna design and how thay will work in the REAL world Not just in a "free space" Pattern Graph.
the informatio is out there as a fact.

you can see the facts Its just up to you to use the information or not.

and as for this subject im done.


Cool

_________________
You can find me Here:
http://www.facebook.com/#!/profile.php?id=100001843308666


Last edited by Radioman193 on Thu Jul 23, 2009 15:15; edited 2 times in total
naiku
DD-WRT User


Joined: 25 Feb 2008
Posts: 51

PostPosted: Thu Jul 23, 2009 15:08    Post subject: Reply with quote
Murrkf wrote:
If the router has two antennas, put them to auto. The router will take care of the traffic...external antenna for the bridge, and internal antenna for the lan inside the house. Plus, there will be a node facing backwards from the external antenna.


Ok, I just looked using Google maps, and from the first house to the second is actually only around 250ft. Does a concrete basement really kill my signal that much that I need a 3rd router? The 1st router is in the basement on the back wall, the 2nd router is in the same house, up one level and in the garage, and then the 3rd router is upstairs (and uphill slightly) from the first house.

Ideally I want to ditch the router in the garage, the added repeater hop takes another chunk out of my bandwidth.

Is a 13dbi panel antenna a good option to mount on the outside of the first house? I can move the router in the second house to a lower level and near a window (but it would be again inside a concrete basment), but on a lower level I could almost get it level with the panel antenna at the first house.
Murrkf
DD-WRT Guru


Joined: 22 Sep 2008
Posts: 12675

PostPosted: Thu Jul 23, 2009 16:05    Post subject: Reply with quote
I would not worry about getting the antennas to the same height from the earth. It really doesn't matter. As long as they can see each other there should be a good signal.

Wifi will not go through a concrete wall well. Antennas don't create a more powerful signals, they create greater sensitivity. If there is no signal for them to sense, because it is blocked by concrete, no antenna will assist. However, if there is a window in the basement, wifi will go through glass reasonably well.

From what I understand of your setup, put the panel antenna outside and point it at the second house. Put the router to auto for antenna choice. Put the router in the second house in the basement window. Set it to auto as well, and put it in repeater mode.

Should work well.

_________________
SIG:
I'm trying to teach you to fish, not give you a fish. If you just want a fish, wait for a fisherman who hands them out. I'm more of a fishing instructor.
LOM: "If you show that you have not bothered to read the forum announcements or to follow the advices in them then the level of help available for you will drop substantially, also known as Murrkf's law.."
Goto page Previous  1, 2, 3, 4, 5, 6, 7, 8  Next Display posts from previous:    Page 6 of 8
Post new topic   This topic is locked: you cannot edit posts or make replies.    DD-WRT Forum Index -> Broadcom SoC based Hardware All times are GMT

Navigation

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You can attach files in this forum
You can download files in this forum