Alternatives to 802.11b bridges

I'm looking for alternatives to 802.11b. I have a 4 mile
stretch that is giving me fits. I have clear line of site
except that a rather large tree sqeezing in on the
fresnel zone about dead center. Does anyone
have any recomendations on Laser/Optical/Etc.
devices? I can't relocate either antenna more than
about 10 feet side-to-side. I feel like a midnight
chain-saw visit is in order.

Oh, and BTW... it has to be inexpensive. ( < $750 ).

Thanks,


Gordon Montgomery
Living Scriptures, Inc
(E-Mail Removed) (anti spam - replace lsi with livingscriptures)
(801) 627-2000

900 mhz radios would probably work but they will set you back a grand.
I maintain and install 802.11b cisco 350's for my employer.
What kind of radios and antennas are you running now?
Sometimes a bit more gain can help with tree interference. It's not the
"right" way but when you are trying to save bucks and only need about a meg
of bandwidth, it will work.
I just finished installing a 40 foot tower at my residence and will be
shooting 2.5 miles to a 400 foot microwave tower that has a ds3 passing
through via nec digital microwave bridged together by a cisco router. I will
be coming out of the router using a cisco 340's shooting to my house via a
24 db gain antenna mounted at 200 feet using lmr 600 coax. I will also have
the same antenna at my house mounted on 40 foot of rohn 25g. I know that I
have a fresnel zone issue about a mile from my house but if I can get over a
meg of bandwith I will be happy. I will be turning off my dsl connection and
my dial tone as I will use vonage for phone service. If it becomes a serious
issue for me I will stack enough tower to resolve the tree issue but I will
have to guy the tower which I really don't want to deal with.
I have imstalled links varying from 100 yards to 20 miles and trees have
givin me fits in the past but usually there is a serious rsl issue also.
But the quality of radios can make a big difference when you are dealing
with a "borderline" issue.


"Gordon Montgomery" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> I'm looking for alternatives to 802.11b. I have a 4 mile
> stretch that is giving me fits. I have clear line of site
> except that a rather large tree sqeezing in on the
> fresnel zone about dead center. Does anyone
> have any recomendations on Laser/Optical/Etc.
> devices? I can't relocate either antenna more than
> about 10 feet side-to-side. I feel like a midnight
> chain-saw visit is in order.
>
> Oh, and BTW... it has to be inexpensive. ( < $750 ).
>
> Thanks,
>
>
> Gordon Montgomery
> Living Scriptures, Inc
> (E-Mail Removed) (anti spam - replace lsi with livingscriptures)
> (801) 627-2000

On Mon, 01 Aug 2005 04:29:23 GMT, (E-Mail Removed) (Gordon Montgomery)
wrote:

>I'm looking for alternatives to 802.11b. I have a 4 mile
>stretch that is giving me fits. I have clear line of site
>except that a rather large tree sqeezing in on the
>fresnel zone about dead center. Does anyone
>have any recomendations on Laser/Optical/Etc.
>devices? I can't relocate either antenna more than
>about 10 feet side-to-side. I feel like a midnight
>chain-saw visit is in order.
>
>Oh, and BTW... it has to be inexpensive. ( < $750 ).

4 miles should be achievable with decent antennas. My guess(tm) is
that you've skimped on the antennas. Could I trouble you to kindly
disclose what hardware you currently have to work with? Let's play
with the numbers. My guess(tm) is that you probalby have some kind of
dedicated point to point bridge radio such as a DLink DWL-900AP+.
I'll also guess(tm) that you've run a bit too much coax cable.
Instead of trying to demonstrate why my guess(tm) of your existing
system doesn't work, I'll see what it takes to make things work.

At 5.5Mbits/sec, the receiver sensitivity is about -85dBm.
Tx power is about +15dBm. My guess is a few feet of coax and
connectors will eat about -4dB. A big dish at 24dBi gain is probably
required at both ends. I'm looking for a minimum of 20dB fade margin.

Running the numbers at:
http://www.terabeam.com/support/calculations/som.php
Distance = 4 miles
Tx power = 15dBm
Tx ant gain = 24dBi
Rx and gain = 24dBi
Tx cable loss = 4dB (including connectors)
RX cable loss = 4dB
RX sens = -85dBm (for 5.5mbits/sec)
Fade margin = ??

That yields a fade margin of 23.8dB which should be workable.
So, if you take your existing unspecified 802.11b wireless bridges,
buy a pair of 24dBi dish antennas for about $60/ea, repackage your
unspecified wireless bridge in an outdoor box with a minumum of coax
cable to the antenna, and install some kind of power over ethernet
system, it will work.

It's difficult to calculate the effects of the tree that is in the
Fresnel zone. I would guess about 6 dB additional loss which may be a
problem. You can compensate by slowing down the connection to
2Mbits/sec. However, that's a bad idea. Instead I suggest you
purchase a pair of 802.11g wireless bridges and run them at the
slowest OFDM data rate of 6Mbit/sec. The will give a receiver
sensitivity of -88dBm, which will buy you 3dB additional fade margin
and additional tolerance to multipath.

You really do not want to know the price of a 4 mile FSO (free space
optical) data link. Try:
http://www.plaintree.com/products.htm
and hold onto your wallet. Plaintree is the lowest cost of the
various FSO vendors.


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
AE6KS 831-336-2558

Back about 40 years ago I saw a 6 Ghz microwave shot installed
over a maybe 70 mile path, with both ends on mountain tops. At
one end they had installed (at *huge* expense on top of an 8500
foot high mountain), a 50 foot free standing tower.

Because of the long path, they experimented to see where the
dish got the best signal, starting at the top of the tower. It
ended up located 12 feet off the ground!

If you have possible path obstructions, do try moving the
antenna up and down a bit. It isn't necessarily just a case of
getting as high as you can...

One other point... 200 feet of LMR600 coax has a loss of nearly
9 dB at 2400Ghz. It would probably be far less expensive *and*
a significant technical improvement to put the radio in a weather proof
housing and mount it on the tower. Even LDF5-50A heliax would be
4 dB loss, which might acceptable but the cost isn't worth 5 dB.


"skeeter" <(E-Mail Removed)> wrote:
>900 mhz radios would probably work but they will set you back a grand.
>I maintain and install 802.11b cisco 350's for my employer.
>What kind of radios and antennas are you running now?
>Sometimes a bit more gain can help with tree interference. It's not the
>"right" way but when you are trying to save bucks and only need about a meg
>of bandwidth, it will work.
>I just finished installing a 40 foot tower at my residence and will be
>shooting 2.5 miles to a 400 foot microwave tower that has a ds3 passing
>through via nec digital microwave bridged together by a cisco router. I will
>be coming out of the router using a cisco 340's shooting to my house via a
>24 db gain antenna mounted at 200 feet using lmr 600 coax. I will also have
>the same antenna at my house mounted on 40 foot of rohn 25g. I know that I
>have a fresnel zone issue about a mile from my house but if I can get over a
>meg of bandwith I will be happy. I will be turning off my dsl connection and
>my dial tone as I will use vonage for phone service. If it becomes a serious
>issue for me I will stack enough tower to resolve the tree issue but I will
>have to guy the tower which I really don't want to deal with.
>I have imstalled links varying from 100 yards to 20 miles and trees have
>givin me fits in the past but usually there is a serious rsl issue also.
>But the quality of radios can make a big difference when you are dealing
>with a "borderline" issue.
>
>"Gordon Montgomery" <(E-Mail Removed)> wrote in message
>news:(E-Mail Removed)...
>> I'm looking for alternatives to 802.11b. I have a 4 mile
>> stretch that is giving me fits. I have clear line of site
>> except that a rather large tree sqeezing in on the
>> fresnel zone about dead center. Does anyone
>> have any recomendations on Laser/Optical/Etc.
>> devices? I can't relocate either antenna more than
>> about 10 feet side-to-side. I feel like a midnight
>> chain-saw visit is in order.
>>
>> Oh, and BTW... it has to be inexpensive. ( < $750 ).
>>
>> Thanks,
>>
>>
>> Gordon Montgomery
>> Living Scriptures, Inc
>> (E-Mail Removed) (anti spam - replace lsi with livingscriptures)
>> (801) 627-2000

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) (E-Mail Removed)

I use ydi 6ghz 45mb (full duplex) tower mounted radios on a link that we
have and every damn time that tower gets hit with lightning it smokes the
radio. I am presently getting ready to move the radios inside the building
and run 300 foot of waveguide, not cheap, but I am tired of calling a tower
crew out to replace the radio. I told the boss when we installed the link
that they would be a headache but it was a money issue. The many times that
we have sent a tower crew up and replaced the radio it would have been
cheaper to run waveguide in the first place. The grounding system is fine
and the megger measured less than 2 ohms.
Talked to too many in the business and know from previous experience. Tower
mounted radios are not reliable in an area with a lot of electrical storms.
"Floyd L. Davidson" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Back about 40 years ago I saw a 6 Ghz microwave shot installed
> over a maybe 70 mile path, with both ends on mountain tops. At
> one end they had installed (at *huge* expense on top of an 8500
> foot high mountain), a 50 foot free standing tower.
>
> Because of the long path, they experimented to see where the
> dish got the best signal, starting at the top of the tower. It
> ended up located 12 feet off the ground!
>
> If you have possible path obstructions, do try moving the
> antenna up and down a bit. It isn't necessarily just a case of
> getting as high as you can...
>
> One other point... 200 feet of LMR600 coax has a loss of nearly
> 9 dB at 2400Ghz. It would probably be far less expensive *and*
> a significant technical improvement to put the radio in a weather proof
> housing and mount it on the tower. Even LDF5-50A heliax would be
> 4 dB loss, which might acceptable but the cost isn't worth 5 dB.
>
>
> "skeeter" <(E-Mail Removed)> wrote:
> >900 mhz radios would probably work but they will set you back a grand.
> >I maintain and install 802.11b cisco 350's for my employer.
> >What kind of radios and antennas are you running now?
> >Sometimes a bit more gain can help with tree interference. It's not the
> >"right" way but when you are trying to save bucks and only need about a
meg
> >of bandwidth, it will work.
> >I just finished installing a 40 foot tower at my residence and will be
> >shooting 2.5 miles to a 400 foot microwave tower that has a ds3 passing
> >through via nec digital microwave bridged together by a cisco router. I
will
> >be coming out of the router using a cisco 340's shooting to my house via
a
> >24 db gain antenna mounted at 200 feet using lmr 600 coax. I will also
have
> >the same antenna at my house mounted on 40 foot of rohn 25g. I know that
I
> >have a fresnel zone issue about a mile from my house but if I can get
over a
> >meg of bandwith I will be happy. I will be turning off my dsl connection
and
> >my dial tone as I will use vonage for phone service. If it becomes a
serious
> >issue for me I will stack enough tower to resolve the tree issue but I
will
> >have to guy the tower which I really don't want to deal with.
> >I have imstalled links varying from 100 yards to 20 miles and trees have
> >givin me fits in the past but usually there is a serious rsl issue also.
> >But the quality of radios can make a big difference when you are dealing
> >with a "borderline" issue.
> >
> >"Gordon Montgomery" <(E-Mail Removed)> wrote in message
> >news:(E-Mail Removed)...
> >> I'm looking for alternatives to 802.11b. I have a 4 mile
> >> stretch that is giving me fits. I have clear line of site
> >> except that a rather large tree sqeezing in on the
> >> fresnel zone about dead center. Does anyone
> >> have any recomendations on Laser/Optical/Etc.
> >> devices? I can't relocate either antenna more than
> >> about 10 feet side-to-side. I feel like a midnight
> >> chain-saw visit is in order.
> >>
> >> Oh, and BTW... it has to be inexpensive. ( < $750 ).
> >>
> >> Thanks,
> >>
> >>
> >> Gordon Montgomery
> >> Living Scriptures, Inc
> >> (E-Mail Removed) (anti spam - replace lsi with livingscriptures)
> >> (801) 627-2000
>
> --
> Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
> Ukpeagvik (Barrow, Alaska) (E-Mail Removed)

In article <(E-Mail Removed)>, Jeff Liebermann <(E-Mail Removed)> wrote:
>On Mon, 01 Aug 2005 04:29:23 GMT, (E-Mail Removed) (Gordon Montgomery)
>wrote:
>
>>I'm looking for alternatives to 802.11b. I have a 4 mile
>>stretch that is giving me fits. I have clear line of site
>>except that a rather large tree sqeezing in on the
>>fresnel zone about dead center. Does anyone
>>have any recomendations on Laser/Optical/Etc.
>>devices? I can't relocate either antenna more than
>>about 10 feet side-to-side. I feel like a midnight
>>chain-saw visit is in order.
>>
>>Oh, and BTW... it has to be inexpensive. ( < $750 ).
>
>4 miles should be achievable with decent antennas. My guess(tm) is
>that you've skimped on the antennas. Could I trouble you to kindly
>disclose what hardware you currently have to work with? Let's play
>with the numbers. My guess(tm) is that you probalby have some kind of
>dedicated point to point bridge radio such as a DLink DWL-900AP+.
>I'll also guess(tm) that you've run a bit too much coax cable.
>Instead of trying to demonstrate why my guess(tm) of your existing
>system doesn't work, I'll see what it takes to make things work.
>
>At 5.5Mbits/sec, the receiver sensitivity is about -85dBm.
>Tx power is about +15dBm. My guess is a few feet of coax and
>connectors will eat about -4dB. A big dish at 24dBi gain is probably
>required at both ends. I'm looking for a minimum of 20dB fade margin.
>
>Running the numbers at:
> http://www.terabeam.com/support/calculations/som.php
> Distance = 4 miles
> Tx power = 15dBm
> Tx ant gain = 24dBi
> Rx and gain = 24dBi
> Tx cable loss = 4dB (including connectors)
> RX cable loss = 4dB
> RX sens = -85dBm (for 5.5mbits/sec)
> Fade margin = ??
>
>That yields a fade margin of 23.8dB which should be workable.
>So, if you take your existing unspecified 802.11b wireless bridges,
>buy a pair of 24dBi dish antennas for about $60/ea, repackage your
>unspecified wireless bridge in an outdoor box with a minumum of coax
>cable to the antenna, and install some kind of power over ethernet
>system, it will work.
>
>It's difficult to calculate the effects of the tree that is in the
>Fresnel zone. I would guess about 6 dB additional loss which may be a
>problem. You can compensate by slowing down the connection to
>2Mbits/sec. However, that's a bad idea. Instead I suggest you
>purchase a pair of 802.11g wireless bridges and run them at the
>slowest OFDM data rate of 6Mbit/sec. The will give a receiver
>sensitivity of -88dBm, which will buy you 3dB additional fade margin
>and additional tolerance to multipath.
>
>You really do not want to know the price of a 4 mile FSO (free space
>optical) data link. Try:
> http://www.plaintree.com/products.htm
>and hold onto your wallet. Plaintree is the lowest cost of the
>various FSO vendors.
>
>

Well, don't laugh. I'm using SMC2682W bridges on each end. Both ends
use 24dBi grid antennas. One end is already mounted at the antenna, maybe
16 inches of coax. The other end has 50 feet of LMR-400. I do have another
link running 9 miles using the same setup for equipment, except both radios
are mounted at the antenna with about 20 inches of coax going to 24 dBi
grids. That ran for years until about the last 8 months I had to add an
amplifier on one end. I just didn't want to go through the hassle of adding
an amp to the 4 mile setup. But maybe I will have to try it.

Oh, and my outdoor box? It is an inverted plastic garbage can, open at the
bottom. I was in a hurry to install the old link, and just grabbed the closest
water-tight thing I found just to get it running quickly. I always meant to
get a _real_ box later, but I just never got around to it. It has been over
3 years now of 100+ degree summers, -5 degree winters and storms
strong enough that I had to re-aim the antenna, but the radio has been
running fine. Someday I'll get that box though.....

Thanks for your help and information.



Gordon Montgomery
Living Scriptures, Inc
(E-Mail Removed) (anti spam - replace lsi with livingscriptures)
(801) 627-2000

In article <(E-Mail Removed)>, "skeeter" <(E-Mail Removed)> wrote:
>900 mhz radios would probably work but they will set you back a grand.
>I maintain and install 802.11b cisco 350's for my employer.
>What kind of radios and antennas are you running now?

I'm running old SMC2682W radios and 24 dBi grid parabolics. They
have been very stable on another link I've been running for more than
3 years now.

>Sometimes a bit more gain can help with tree interference. It's not the
>"right" way but when you are trying to save bucks and only need about a meg
>of bandwidth, it will work.

I'll have to try that.

>I just finished installing a 40 foot tower at my residence and will be
>shooting 2.5 miles to a 400 foot microwave tower

That would be great if I could install towers, but the location prohibits it.
And the cost would be extreme for this project.

Thanks for your input.



Gordon Montgomery
Living Scriptures, Inc
(E-Mail Removed) (anti spam - replace lsi with livingscriptures)
(801) 627-2000

"skeeter" <(E-Mail Removed)> wrote:
>I use ydi 6ghz 45mb (full duplex) tower mounted radios on a link that we
>have and every damn time that tower gets hit with lightning it smokes the
>radio. I am presently getting ready to move the radios inside the building
>and run 300 foot of waveguide, not cheap, but I am tired of calling a tower
>crew out to replace the radio. I told the boss when we installed the link
>that they would be a headache but it was a money issue. The many times that
>we have sent a tower crew up and replaced the radio it would have been
>cheaper to run waveguide in the first place. The grounding system is fine
>and the megger measured less than 2 ohms.
>Talked to too many in the business and know from previous experience. Tower
>mounted radios are not reliable in an area with a lot of electrical storms.

Yep. I'll agree to that!

The redeeming feature you have is the use of very high gain
antennas, which more than make up for the loss in receiver
sensitivity due to the long run of coax.

Sounds like you are stuck with it...

>"Floyd L. Davidson" <(E-Mail Removed)> wrote in message
>news:(E-Mail Removed)...
>> Back about 40 years ago I saw a 6 Ghz microwave shot installed
>> over a maybe 70 mile path, with both ends on mountain tops. At
>> one end they had installed (at *huge* expense on top of an 8500
>> foot high mountain), a 50 foot free standing tower.
>>
>> Because of the long path, they experimented to see where the
>> dish got the best signal, starting at the top of the tower. It
>> ended up located 12 feet off the ground!
>>
>> If you have possible path obstructions, do try moving the
>> antenna up and down a bit. It isn't necessarily just a case of
>> getting as high as you can...
>>
>> One other point... 200 feet of LMR600 coax has a loss of nearly
>> 9 dB at 2400Ghz. It would probably be far less expensive *and*
>> a significant technical improvement to put the radio in a weather proof
>> housing and mount it on the tower. Even LDF5-50A heliax would be
>> 4 dB loss, which might acceptable but the cost isn't worth 5 dB.
>>
>>
>> "skeeter" <(E-Mail Removed)> wrote:
>> >900 mhz radios would probably work but they will set you back a grand.
>> >I maintain and install 802.11b cisco 350's for my employer.
>> >What kind of radios and antennas are you running now?
>> >Sometimes a bit more gain can help with tree interference. It's not the
>> >"right" way but when you are trying to save bucks and only need about a
>meg
>> >of bandwidth, it will work.
>> >I just finished installing a 40 foot tower at my residence and will be
>> >shooting 2.5 miles to a 400 foot microwave tower that has a ds3 passing
>> >through via nec digital microwave bridged together by a cisco router. I
>will
>> >be coming out of the router using a cisco 340's shooting to my house via
>a
>> >24 db gain antenna mounted at 200 feet using lmr 600 coax. I will also
>have
>> >the same antenna at my house mounted on 40 foot of rohn 25g. I know that
>I
>> >have a fresnel zone issue about a mile from my house but if I can get
>over a
>> >meg of bandwith I will be happy. I will be turning off my dsl connection
>and
>> >my dial tone as I will use vonage for phone service. If it becomes a
>serious
>> >issue for me I will stack enough tower to resolve the tree issue but I
>will
>> >have to guy the tower which I really don't want to deal with.
>> >I have imstalled links varying from 100 yards to 20 miles and trees have
>> >givin me fits in the past but usually there is a serious rsl issue also.
>> >But the quality of radios can make a big difference when you are dealing
>> >with a "borderline" issue.
>> >
>> >"Gordon Montgomery" <(E-Mail Removed)> wrote in message
>> >news:(E-Mail Removed)...
>> >> I'm looking for alternatives to 802.11b. I have a 4 mile
>> >> stretch that is giving me fits. I have clear line of site
>> >> except that a rather large tree sqeezing in on the
>> >> fresnel zone about dead center. Does anyone
>> >> have any recomendations on Laser/Optical/Etc.
>> >> devices? I can't relocate either antenna more than
>> >> about 10 feet side-to-side. I feel like a midnight
>> >> chain-saw visit is in order.
>> >>
>> >> Oh, and BTW... it has to be inexpensive. ( < $750 ).
>> >>
>> >> Thanks,
>> >>
>> >>
>> >> Gordon Montgomery
>> >> Living Scriptures, Inc
>> >> (E-Mail Removed) (anti spam - replace lsi with livingscriptures)
>> >> (801) 627-2000
>>
>> --
>> Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
>> Ukpeagvik (Barrow, Alaska) (E-Mail Removed)

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) (E-Mail Removed)

One point I would make is to say that when wet, trees (water) absorb
the signal, this can be a major issue so bear it in mind.


On Mon, 01 Aug 2005 04:29:23 GMT, (E-Mail Removed) (Gordon Montgomery)
wrote:

>I'm looking for alternatives to 802.11b. I have a 4 mile
>stretch that is giving me fits. I have clear line of site
>except that a rather large tree sqeezing in on the
>fresnel zone about dead center. Does anyone
>have any recomendations on Laser/Optical/Etc.
>devices? I can't relocate either antenna more than
>about 10 feet side-to-side. I feel like a midnight
>chain-saw visit is in order.
>
>Oh, and BTW... it has to be inexpensive. ( < $750 ).
>
>Thanks,
>
>
>Gordon Montgomery
>Living Scriptures, Inc
>(E-Mail Removed) (anti spam - replace lsi with livingscriptures)
>(801) 627-2000

Drop the ZZZ to reply

Cheers ...

In article <(E-Mail Removed)>, (E-Mail Removed) wrote:
>One point I would make is to say that when wet, trees (water) absorb
>the signal, this can be a major issue so bear it in mind.
>
>

Yes, I am aware of that. Luckily, it has not rained here for 45
days.


Gordon Montgomery
Living Scriptures, Inc
(E-Mail Removed) (anti spam - replace lsi with livingscriptures)
(801) 627-2000