The CATFISH thread - external antenna choice and use.

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lurch2012
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Joined: 24 Sep 2008
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PostPosted: Fri May 08, 2009 19:42    Post subject: Reply with quote
I'm really struggling with something here...It is incredibly difficult to decide on an antenna with all the choices.
Here is my situation:

I am within about a mile of high speed internet service, but have been unable to convince the ISP to help me out here. I have negotiated a deal with 2 of my neighbors in which I help them with their ISP bill in exchange for access. I realize this violates the TOS, but I really don't have much of a choice (I already tried both HughesNet and WildBlue). The only problem is, they don't want any modifications to their network setup or home. In other words, I can't do directionals pointed at each other...

I will be using a Buffalo WHR-54GS using DD-WRT (don't have version on hand, will upgrade if necessary) transmitting at 85mw. As suggested, I will only amplify if absolutely necessary.

I will be mounting the antenna on either a 30 ft pole or on the peak of my home. Either way, I can get about 30 ft of elevation. I will be using an external enclosure to ensure the shortest possible cable length.

The land is flat. In fact, most of the distance between me and my potential AP's are corn fields. There are a few trees (the dense forest of trees near hotspot 1 has been leveled).

The distance between House and Hotspot1: 1.11 miles

The distance between House and Hostpot2: 1.41 miles

Considering the distance and height of mount point, does anyone have an antenna recommendation?

I've pretty much decided against a cantenna because there are some pretty fierce winds that come across the fields. From what I've read on this post and the linked information I should be looking at a yagi/parabolic and I am leaning toward a Parabolic dish such as...
http://www.fab-corp.com/product.php?productid=2431&cat=251&page=1

With out being able to boost the hotspots, am I wasting my time?

A Google Earth image is attached.

Any help is greatly appreciated.



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Murrkf
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PostPosted: Fri May 08, 2009 19:48    Post subject: Reply with quote
I would start with a dish, for that distance. A Yagi might do it. Do you have absolutely clear line of sight all year? That bush by the road looks bad. Is it completely gone now? The other site might be better if it isn't.
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lurch2012
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Joined: 24 Sep 2008
Posts: 8

PostPosted: Fri May 08, 2009 20:05    Post subject: Reply with quote
Murrkf wrote:
I would start with a dish, for that distance. A Yagi might do it. Do you have absolutely clear line of sight all year? That bush by the road looks bad. Is it completely gone now? The other site might be better if it isn't.


I'm not sure that I have clear LoS right now because it is such a great distance and I haven't been up 30ft. I do know there would be a handful of trees between either spot 1 or spot 2. I'll grab some binoculars and get on my roof when I get home to make check.

The large section of forest on the west side of that highway is gone completely.
lurch2012
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Joined: 24 Sep 2008
Posts: 8

PostPosted: Fri May 08, 2009 20:15    Post subject: Reply with quote
So...assuming questionable LoS (only trees would block the path), is 19 dbi enough? I'm told that when deciding on an antenna, overkill is the best policy.
barryware
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Joined: 26 Jan 2008
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PostPosted: Fri May 08, 2009 20:17    Post subject: Reply with quote
lurch2012 wrote:
overkill is the best policy.


Just like the rest of life.. You can never have too much.

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robert-e
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Joined: 19 Feb 2007
Posts: 227

PostPosted: Fri May 08, 2009 20:37    Post subject: Reply with quote
I have done just what you are attempting. I used a wrt54gl running in repeater mode, placed on top of a 20 foot pole, connected to a 24 dB grid parabolic antenna with a 3 foot length of low loss coax. Pointing was critical; I used the "Site Survey" in DDWRT, changing the direction in small increments at a time. The other end had a standard Wifi system. Path was 100% stable. We tested this with a 6 mile path, and it still worked. I think we might have done even better if the AckTime variable had worked (it was an older vers. of DDWRT, it should be fixed by now?)
Your distance of abt 1 miles clear LOS should be a piece of cake.
Regards,
Bob

Edit...Yes, an 18 dB antenna will be more than enough for tha path. You could even use a patch antenna at your end. Certainly, if you could use a patch at both ends, that would be super good.
B
lurch2012
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Joined: 24 Sep 2008
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PostPosted: Fri May 08, 2009 20:47    Post subject: Reply with quote
robert-e wrote:
I have done just what you are attempting. I used a wrt54gl running in repeater mode, placed on top of a 20 foot pole, connected to a 24 dB grid parabolic antenna with a 3 foot length of low loss coax. Pointing was critical; I used the "Site Survey" in DDWRT, changing the direction in small increments at a time. The other end had a standard Wifi system. Path was 100% stable. We tested this with a 6 mile path, and it still worked. I think we might have done even better if the AckTime variable had worked (it was an older vers. of DDWRT, it should be fixed by now?)
Your distance of abt 1 miles clear LOS should be a piece of cake.
Regards,
Bob



I just purchased the following antenna:

http://www.fab-corp.com/product.php?productid=2894

Just talked to my neighbor at point 2, and he uses dd-wrt as well. This could be a easy. *crosses fingers*

Thanks for the "Site Survey" tip and I'll be sure and update the firmware to latest version before I get started.

I'm not sure on the ACK timing. I have seen on other posts that it creates problems. I just have no idea what it is. I guess I'll cross that bridge when I get there.

Just out of curiosity (and maybe a dumb question)...what kind of latency could I expect out of an operation like this? ballpark
robert-e
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Joined: 19 Feb 2007
Posts: 227

PostPosted: Fri May 08, 2009 20:53    Post subject: Reply with quote
Latency? Not much more than a direct wireless connect (I assume you are using a repeater mode). Certainly, after using Hughesnet, you will find the low latency delightful. IIRC, ping times to the dns server were around 70 ms.
Hope this helps.
Bob

Oh yes, that antenna will work well. I don't think you will have a problem even if the other end is using stock antennae, unless their router is in the basement or some such.
B
lurch2012
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Joined: 24 Sep 2008
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PostPosted: Fri May 08, 2009 21:09    Post subject: Reply with quote
robert-e wrote:
Latency? Not much more than a direct wireless connect (I assume you are using a repeater mode). Certainly, after using Hughesnet, you will find the low latency delightful. IIRC, ping times to the dns server were around 70 ms.
Hope this helps.
Bob

Oh yes, that antenna will work well. I don't think you will have a problem even if the other end is using stock antennae, unless their router is in the basement or some such.
B


Excellent!

Thanks for your help, and I'll be taking pictures of the process for anyone else interested in a similar operation.
Murrkf
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Joined: 22 Sep 2008
Posts: 12675

PostPosted: Fri May 08, 2009 22:17    Post subject: Reply with quote
I agree with all that robert-e said. Ack timing will not cause you problems....it just might not do anything!

Site survey is a good tip, but using netstumbler at the far end might work better.

When this works, you just shake your head and marvel at technology.

When it work! Laughing

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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.
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ad5mb
DD-WRT User


Joined: 12 Oct 2008
Posts: 386

PostPosted: Sat May 09, 2009 1:38    Post subject: Reply with quote
fab corp makes a good product; I recommended them to my employer.

running the numbers:

http://www.terabeam.com/support/calculations/som.php#calc

2450 mHz ( middle of the band )
2.1 dBi TX antenna gain ( lowest realistic number )
0 cable loss ( antenna on router )
15 dBm TX ( standard home router )
1.41 miles
24 db RX antenna gain
2.2 db cable loss ( 33 feet of LMR-400 )

= a very marginal -68.5 db signal at your end.

a 15 dbi antenna at the far end = a very respectable -55.6 dBm at your end

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KeithB
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Joined: 22 Jun 2008
Posts: 489

PostPosted: Sat May 09, 2009 16:05    Post subject: Reply with quote
I'll second what ad5mb said about FABcorp. They are the first source from which I purchased replacement antennas for my original WRT54G v1 router. Good people and good products. Very Happy
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strapabiro
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Joined: 25 Dec 2008
Posts: 80

PostPosted: Fri Jun 19, 2009 19:50    Post subject: Reply with quote
Hi, i would like to know which is the bigest (and optimal) omnidirectional antenna (2x because of the 2 antennas?) that a WRT54GL can support with it's internal amp and it's approx. range too, link, price, solution please. A neighbour would like to join my network but he's not in the coverage area of my wds network so i'd like it to extend, without additional cables, powersources, amps, dishes that would make my house look like a telecom centre. Thanks in advance.
Murrkf
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Joined: 22 Sep 2008
Posts: 12675

PostPosted: Fri Jun 19, 2009 22:08    Post subject: Reply with quote
strapabiro wrote:
Hi, i would like to know which is the bigest (and optimal) omnidirectional antenna (2x because of the 2 antennas?) that a WRT54GL can support with it's internal amp and it's approx. range too, link, price, solution please. A neighbour would like to join my network but he's not in the coverage area of my wds network so i'd like it to extend, without additional cables, powersources, amps, dishes that would make my house look like a telecom centre. Thanks in advance.


You need to explain things a little more precisely. How far away is the neighbour. Line of sight? Who gets the router? How will he be connected to your network (hardware). Why would you want omni for this. The GL can hook to any antenna you can legally give it. You don't need an amp. You only need and want one antenna attached to the 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.."
strapabiro
DD-WRT User


Joined: 25 Dec 2008
Posts: 80

PostPosted: Fri Jun 19, 2009 23:39    Post subject: Reply with quote
Murrkf wrote:
strapabiro wrote:
Hi, i would like to know which is the bigest (and optimal) omnidirectional antenna (2x because of the 2 antennas?) that a WRT54GL can support with it's internal amp and it's approx. range too, link, price, solution please. A neighbour would like to join my network but he's not in the coverage area of my wds network so i'd like it to extend, without additional cables, powersources, amps, dishes that would make my house look like a telecom centre. Thanks in advance.


You need to explain things a little more precisely. How far away is the neighbour. Line of sight? Who gets the router? How will he be connected to your network (hardware). Why would you want omni for this. The GL can hook to any antenna you can legally give it. You don't need an amp. You only need and want one antenna attached to the router.


The neighbour lives like 200 m away from me, but i was thinking if i give away money for an antenna i could buy a better one, who knows. (better in the way of gain and coverage) The router would go up into my attic after i'd install the antenna, that will give a line of sight.
Omni because some other neighbours are wired to the router on the opposite direction a bit closer so they could go wireless too ... i hate dish, yagi and everything else that requres more than a pigtail between the router and the antenna. I'd like to keep it simple yet practical. About his connection, he didn't bought a wifi card yet. (Now dont tell me that distance is enough with the factory antennas too because i roamed around the streets and the signal is already very weak after 150 m, or there's something wrong with my settings.) Thank you in advance.
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