wifi antenna in the mountains

Have a question or want to start a discussion? Post it! No Registration Necessary.  Now with pictures!

Threaded View


I've spent a dozen hours looking for a solution to my situation, and
I'm only finding parts of the answer.  Here's the deal.

I live in a beautiful canyon 4 miles from the valley/city.  A peak 600
feet from my house has line of sight to the city where there are WISP
towers.  Likewise, I have line of site from my front door to the peak
600 feet away.   I can build a biquad antenna and put it on that point
and it receives a signal (tested with my laptop), but I'm stuck after
that.

Obstacle 1. There's no electrical power plug on the peak.
a.  I'm not comfortable running power/conduit that distance (and I'm
sure there are ordanances against that)
b. The distance is too far for Power Over Ethernet

Obstacle 2. How to get the signal from the bi-quad to my home:
a. The distance is too far for Cat5 cable, and there's no way to power
any in-line repeaters
b. I could run fiber cable, but that requires power at the antenna
c. I could run old ThickNet 10-base-5 cable, but that requires power at
the antenna

So, a couple exotic ideas I have:
Is it possible to build a bi-quad that captures the signal without
power or only with simple batteries, then use a cantenna at my house
pointed to the bi-quad?
Can I build some sort of reflector on the point such as a mirror or
metal sheet, then locate the bi-quad at my house and point it at the
reflector?

Are there other viable options?  Looking for some creative ideas here.

Thanks in advance


Re: wifi antenna in the mountains


Why not just get satellite internet?  Is this a hobby project?  Anyways, it
seems that power is your problem here.  I am interested inseeing what people
come up with.

K

Quoted text here. Click to load it



Re: wifi antenna in the mountains



Quoted text here. Click to load it
I agree. Is solar and/or wind power and a car battery a viable option?

Paul



Re: wifi antenna in the mountains


Paul wrote:
Quoted text here. Click to load it
Sheesh, how about just using a passive repeater ??

Re: wifi antenna in the mountains


youcantoo wrote:
Quoted text here. Click to load it

Exactly what I was thinking. getwilde, just take two decent antennas,
grid parabolics would be nice and not necessarily all that expensive,
and hook them up with a bit of coax running from one antenna to the
other. Aim one at your house, one at the WISP. No electronics involved
so no need of elecjuicity.

Re: wifi antenna in the mountains


Oh, now you've got me excited.  I figured juice would be required
between antennas (but I'm still trying to learn all of the principles
involved).  If I were to build a passive setup like Roger explains, do
I decrease range by not having power?  The 4 or 5 miles to the Acess
Point worries me a bit.

So, am I thinking about this right...? To increase range:  Is adding an
amplifier at my house the best way to increase the outgoing signal,
even though it will be passing through the passive antenna?  Likewise,
if the grid parabolic pointed at the WISP is larger, is that the best
way to increase incoming reception?  (Assuming I build the whole setup
well)

Incidentally, yes, solar and a car battery are options, but a huge
hassle if I can avoid them (and I would run the risk of having them
stolen at some point).  But if I were told that power at the middle
antenna is the only way to insure good range, then I'd definitely
explore that further.  I'd even be willing to march up there every few
weeks to replace batteries (skip the solar power thing altogether), if
power requirements were low enough to make a small battery rack an
option.


Re: wifi antenna in the mountains


Me wrote:

Quoted text here. Click to load it

Ack!  As a satellite internet user, I'd jump through more hoops than the OP
is facing to get service from a WISP!

Quoted text here. Click to load it

OK, that's an obstacle.  You could probably solve it with a solar panel and
a battery - but theft could be a problem.  It would still be my choice.

Quoted text here. Click to load it

No, it isn't.  I know the standard specifies 100m, but Jeff will tell you he
runs it 1000'

--
derek

Re: wifi antenna in the mountains


I've considered satellite, but I'd prefer higher speeds, less latency,
and lower costs. Not having a phone line might also be an issue... but
I'll only explore that further if I can't get this wi-fi approach
working.


Re: wifi antenna in the mountains


getwilde wrote:
Quoted text here. Click to load it
You should investigate placing a decent gain passive radiator on the
high spot and a good gain antenna at the home , some simple testing with
the laptop will confirm this suggestion but do remember the passive
needs specific high gain and careful installation , good luck

Re: wifi antenna in the mountains


On Sat, 19 Nov 2005 00:41:07 +1000, ReginaldP

Quoted text here. Click to load it

Do you have any idea how large the passive reflector will need to be
at 600ft in order to make this useable?  At 2.4GHz, the highest gain
antenna is about 24dBi with a 7 degree beamwidth.  At 600ft, that beam
is 74ft wide.  With a 45 degree tilt angle, that's a 103 x 103 ft
diameter reflector.  Anything less will result in corresponding loss
of signal.  Half the size = 1/4th the area = -12dB loss.

I can work the numbers in detail if you want, but such arrangements
never work at 2.4Ghz.  See references under "periscope antennas".

--
Jeff Liebermann     jeffl@comix.santa-cruz.ca.us
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Re: wifi antenna in the mountains


Jeff Liebermann wrote:
Quoted text here. Click to load it
Dont get your tits in a tangle Jeffy , I was reading passive repeater
which should do the job , I have built something very similar with
success and it is certainly worth looking at , do the figures if you want .

Re: wifi antenna in the mountains


ReginaldP wrote:

Quoted text here. Click to load it
Rethinking it I'm wondering is running some 2.4 mm cable twin up there
and feeding 24ac to a ap at the top is feasible , I guess we wont really
know unless some one does a walk over and posts some measurements of rx
sigs at the hill top .

Re: wifi antenna in the mountains


On Sat, 19 Nov 2005 13:55:18 +1000, ReginaldP

Quoted text here. Click to load it

It might be a problem because the distance to the access point is 4
miles (6.44km) distant and we have no clue as to what type of antenna
system is at the access point end.  I ran the numbers in:
|
http://groups.google.com/group/alt.internet.wireless/msg/747ce1170e173e8b?fwc=1
near the bottom starting with "Much more interesting is..."
Just ignore my dumb idea of running 600ft of coax cable.  

My guess(tm) is that unless the access point has a directional
(sector) antenna system or much higher gain omni, a 4 mile link may be
functional, but not very reliable.  However, the fact that it almost
works with a biquad antenna leads me to suspect that a bigger antenna
may do the trick.

--
Jeff Liebermann  150 Felker St #D Santa Cruz CA 95060
831.336.2558 voice        
http://www.LearnByDestroying.com           AE6KS
http://802.11junk.com Skype: JeffLiebermann
jeffl@comix.santa-cruz.ca.us    jeffl@cruzio.com


Re: wifi antenna in the mountains


Jeff Liebermann wrote:

Quoted text here. Click to load it
Exactly my point , of course you made some guesses but if the gent takes
a walk and makes some measurements with what he has ...

Re: wifi antenna in the mountains


Quoted text here. Click to load it


You could do something solar powered on the peak.

Cringely has a writeup about using passive repeaters in the same situation,
with no power required.
http://www.pbs.org/cringely/pulpit/pulpit20010628.html
http://www.pbs.org/cringely/pulpit/pulpit20010712.html
Some people question that he actually accomplished this.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA  38.8,-122.5


Re: wifi antenna in the mountains



Quoted text here. Click to load it

This is good news.  This should be no problem.

Quoted text here. Click to load it

Wrong on both counts.  I've run all kinds of power through the forest.
As long as you don't cross any major boundaries (roads, property
lines, etc), you're fine.  Low voltage power is not considered a fire
hazzard.  Xmas tree lamps draw more power and get hotter than a
typical access point.

In addition, you can run up to about 1000ft of CAT5 at 10baseT-HDX
speeds.  I've scribbled several postings in this newsgroup on the
topic.  You can also use coaxial cable for about the same distances
using RG-6/U and 10base-2 using media converters.  Of course, you can
also use fiber, but that's a bit more expensive and overkill.
http://groups.google.com/group/alt.internet.wireless/msg/f1e3a5e2b13d0793

Let's grind the numbers for running power up the hill.  I'll use 700ft
because there will probably be some snaking of the wire.  I'll assume
you'll use an ethernet bridge radio or one that supports client mode.
I suggest a Linksys WRT54G (NOT v5) with DD-WRT firmware.  The nice
part of this device is that it has a very wide range switching
regulator which will run the box on anything between about 4 and
18VDC.  This is critical for delivering power.  I forgot how much
power it draws but I'll guess about 8 watts max.

Start with some higher voltage at the house, run 600ft of wire, and
want at least 6VDC at the access point, at a current drain of about
1.3 amps (at 6VDC).  So, how much voltage does it require?

Well, you can almost do it with CAT5 cable, which has a resistance of
3 ohms per 100ft per conductor.  With 2 conductors in parallel, that's
3 ohms/100ft loop resistance.  600ft would have 18 ohms loop
resistance.  The approximate current drain is:
  8 watts / 6 volts = 1.33Amps
Therefore, the voltage drop across the cable is:
  1.33A * 18 ohms = 24VDC.
So, if you start with a 24VDC power supply, and take the loss in the
cable, you get 6VDC at the WRT54G.  

Unfortunately, the power dissipated in the cable is too high:
  1.33A * (24 - 6V) = 24 watts
It won't melt the cable but it will get quite warm.  Bad idea.

So, we use heavier cable.  I suggest outdoor low voltage UV proof
rubberized cable used for garden flood lights and outdoor low voltage
wiring.  It's typically about #14AWG which is about 0.25 ohms/100ft
per conductor.

Grinding the same 600ft length at 1.33A, I get:
  1.33A * 3 ohms = 4 volts
So, we start with 10VDC, lose 4 volts in the cable, and end up with 6
volts at the WRT54G.  Power dissipation is:
  1.33A * (10 - 4v) = 8 watts
which is still a bit high, but workable.

In reality, starting with 12VDC makes more sense.  The current drain
is somewhat less than 1.33A.  8 watts over 600ft is a bit too high so
I would use some heavier wire if available.  The important point is
that it will work by running a power cable and either CAT5 or RG-6/u
if the radio has a wide range of acceptable power supply voltages.

I can answer the RF questions below if running power is unacceptable.

Quoted text here. Click to load it
--
Jeff Liebermann     jeffl@comix.santa-cruz.ca.us
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Re: wifi antenna in the mountains


Thanks to everyone for the great ideas.  Jeff, thank you for your
detailed response.  It's obvious that you're very knowledgable in this
area.

Regarding passive antennas: A bit more research shows that they're
commonly referred to as "Passive Reflectors".  Google reveals all sorts
of information about them.  With guidance from XReXXwifiX, I've located
Cringely's claim to success
(http://www.pbs.org/cringely/pulpit/pulpit20020207.html ).  However,
Jeff, your response about the size area of the signal after travelling
600 feet makes a lot of sense, and really brings into question
Cringely's credibility.  Unfortunately.  :(

Jeff, thank you for crunching those numbers regarding power cables.
Sounds like a more viable option than I originally thought it to be.
Maybe this is the route to go, combined with running the signal across
cat-5 at half-duplex and lower speed (10baseT-HDX). (I may still be
missing something??? -- Still need to give this more though and
research.)

However, Jeff, you have me extremely curious now with your comment "I
can answer the RF questions below if running power is unacceptable."
If you would be willing to explain this, I would really appreciate it!
It probably opens up options I've erroneously ruled out or don't even
know exist.

Thanks in advance.


Re: wifi antenna in the mountains



getwilde wrote:
Quoted text here. Click to load it

Sorry, I meant to type "Passive Repeaters".


Re: wifi antenna in the mountains


Quoted text here. Click to load it

Everybody thinks so at first.

Quoted text here. Click to load it

It does seem a little awkward and non-reproducible.  But these are
antennas.  Jeff was talking about how large a flat passive reflector would
need to be.  That's a different thing.

Quoted text here. Click to load it

I missed the fact that it is only 600 feet.  I was thinking of my own
environment, where there's a handy peak, but it's about 1000 feet as the
crow flies, across a road, and on someone else's property.

Would it still be on your property?  

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA  38.8,-122.5


Re: wifi antenna in the mountains


d...@XReXXwifiX.usenet.us.com wrote:
Quoted text here. Click to load it

The peak is not my personal property, but part of the community share
that I pay into annually.  The land is unused -- just a bunch of scrub
oak, and I'm quite certain the board will grant me permission to place
an antenna (or small-ish reflector) up there if it's not visible from
the road.  I'm less certain that I can convince them that a low-voltage
power wire is safe to run up there, but I'm definitely ready to discuss
it with them if it turns out to be the best approach!

d...@XReXXwifiX.usenet.us.com wrote:
Quoted text here. Click to load it

Ahhh.  Didn't notice the word "reflector".  I figured we were talking
about 103 ft diameter dish or something!  I've found comments that
"corrugated metal sheets" (with their sine wave-shaped crosscut) work
well as reflectors.  Makes me wonder if I could somehow reduce the 600
ft distance (by running power and an antenna even further out on my own
property), then mount a smaller sheet.  Also makes me wonder if the
radio/cell towers located 1/3 mile away from the house have passive
reflectors already mounted that I could use. (Not likely based on the
size issue Jeff brought up. There's also the question of legality.)


Site Timeline