Yagi Best Antenna??

I am interested in purchasing 2 antennas for a wireless network that I
am setting up between two houses. These are two houses that are out in
the country, about 200 yards away from each other, but there are woods
in-between the two houses. I am not sure what type of antenna that
would be best to get. I thought about getting two 16 Element
Weatherproof Yagi antenna's.

http://www.radiolabs.com/products/an.../18eleyagi.php

I am not sure if this is the best choice I could make. Could you
please give me any reccomendations that you have regarding what type of
antenna I should use.

Thanks for the help.

On 6 Aug 2005 06:09:45 -0700, "inthepickle" <(E-Mail Removed)>
wrote:

>I am interested in purchasing 2 antennas for a wireless network that I
>am setting up between two houses. These are two houses that are out in
>the country, about 200 yards away from each other, but there are woods
>in-between the two houses. I am not sure what type of antenna that
>would be best to get. I thought about getting two 16 Element
>Weatherproof Yagi antenna's.
>
>http://www.radiolabs.com/products/an.../18eleyagi.php

Ah, a perfect bird roost. The local avian population will love it. I
hope you enjoy cleaning the bird droppings off the antenna.

Hmmm... $90 for 15dBi or $6/dB of gain.

Now, if you bought a 19dBi dish antenna, it would cost $41 or $2/dB of
gain. See:
http://www.fab-corp.com
I like dish and panel antennas.

At 200 yards, almost anything over about 8dBi gain will function
except for the trees. The trees are going to be a big problem
depending on how dense they are. You can sometime shoot *UNDER* the
tree canopy at trunk level as there's more space between the trunks
and between the branches. I did that once in an orange grove, which
worked just fine except when someone parks a truck in the beam path.
It's difficult to predict the effects of trees and leaves as it
depends on the thickness of the shrubbery. Can you see through the
leafs? How many yards of foliage is in the way? What type of leafs
(needle, thin leaf, thick leaf, wall of wood, etc)?

Where is your unspecified radio going to be located? Coax cable
losses are substantial and will negate any antenna improvements if
done wrong. You might consider mounting your unspecified wireless
radios near the antennas. Also, be sure to waterproof any exposed
coax connectors.

In general, OFDM does MUCH better than CCK for getting through foliage
via multiple paths. Therefore, I would disable 802.11b speeds in your
unspecified routers. I've found it more reliable to run at a fixed
speed, usually 6, 9, or 12Mbit/sec OFDM. If the signal varies
radically as the wind blows the trees around, you might try a fixed
speed.


--
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

inthepickle wrote:

> I am interested in purchasing 2 antennas for a wireless network that I
> am setting up between two houses. These are two houses that are out in
> the country, about 200 yards away from each other, but there are woods
> in-between the two houses. I am not sure what type of antenna that
> would be best to get. I thought about getting two 16 Element
> Weatherproof Yagi antenna's.
>
> http://www.radiolabs.com/products/an.../18eleyagi.php
>
> I am not sure if this is the best choice I could make. Could you
> please give me any reccomendations that you have regarding what type of
> antenna I should use.
>
> Thanks for the help.
>
Hi,
Yagi (Yagi Uda) antenna is gain antenna. The more element, the more
gain. Higher gain means narrower beam of angle and higher F/B ratio.
You'll have to experiment setting up from both ends for best signal
strength. Think LOS(ling of sight). Radio wave LOS is not as straight as
visual LOS tho.
Good luck,
Tony

On Sat, 06 Aug 2005 19:26:18 GMT, Tony Hwang <(E-Mail Removed)> wrote:

>Yagi (Yagi Uda) antenna is gain antenna. The more element, the more
>gain. Higher gain means narrower beam of angle and higher F/B ratio.

50% wrong. The higher the gain, the narrower the beamwidth for a
given class of antenna. Different types of antennas have different
beamwidths for identical gain antenna.

-3dB beamwidth for different gain yagi antennas:
gain -3db beamwidth
dBi degrees
8 60
10 40
14 30
16 25

-3dB beamwidth for different types of antennas of roughly the same
gain:
Type gain -3dB Beamwidth
dBI degress
patch 13 38
yagi 14 30
planar 13 25
dish 15 19

Note that at 200 yards, even the narrowest antenna (dish) will still
have a wide enough beamwidth to avoid alignment problems.

The front to back ratio (f/b) and sidelobes are a function of the
design of the antenna and has little to do with the gain. It is
possible to trade f/b ratio for gain on most antennas and optimize for
one or the other. However, higher gain antennas do not automatically
imply a higher f/b ratio. Actually, it's quite the opposite as high
gain yagi's tend to leak more than low gain yagi's.

>You'll have to experiment setting up from both ends for best signal
>strength. Think LOS(ling of sight). Radio wave LOS is not as straight as
>visual LOS tho.

Line of sight is ALWAYS a straight line. No curvature involved,
especially at 200 yards. I think you're thinking about Fresnel Zone
clearance, which requires more unobstructed clearance at midpoint than
visual clearance. At 2.4Ghz and 200 yards, the midpoint Fresnel zone
clearance for one zone is 7.8ft radius. However, that's academic as
the trees will probably cause more problems than the lack of Fresnel
zone clearance.


--
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

On Sat, 06 Aug 2005 19:26:18 GMT, Tony Hwang <(E-Mail Removed)> wrote:

>inthepickle wrote:
>
>> I am interested in purchasing 2 antennas for a wireless network that I
>> am setting up between two houses. These are two houses that are out in
>> the country, about 200 yards away from each other, but there are woods
>> in-between the two houses. I am not sure what type of antenna that
>> would be best to get. I thought about getting two 16 Element
>> Weatherproof Yagi antenna's.
>>
>> http://www.radiolabs.com/products/an.../18eleyagi.php
>>
>> I am not sure if this is the best choice I could make. Could you
>> please give me any reccomendations that you have regarding what type of
>> antenna I should use.
>>
>> Thanks for the help.

You might consider 2 homemade tin can waveguide antennas looking at
each other. They are high gain, as good or better than a yagi,
extremely cheap and simple make. Many designs are on the net. I have
one on the end of 30 feet of RG-6 75 ohm CATV cable linking with a
router with stock omni antenna 400 feet away through an apple tree and
it gets 90% signal (-56dbi) at a solid 54mbs.

Two 3.25 by 5 inch (ribed) pet food cans soldered together to make a
10 inch tube (waveguide) closed at one end. Solder a 7/32 dia by 3/8
long brass tube at 90 deg to the side of the can up 2.5 inch from the
closed end. Use a drill same as the I/D of the brass tube and drill
through the can making a clean hole. Obtain a sufficient length of 75
ohm 18 ga (no its not 50 ohm) low loss foam core CATV cable and
measure 1.25 inch from the end then cut through circumference to the
inner conductor. Twist and remove the covering, braid and dialectric
core leaving just 1.25 inch of exposed inner conductor. Insert this
into the brass tube and push it down firmly so the tube slides under
the braid and over the foil wrap until the foam dialectric is flush
with the inside of the can thus forming a 1.25 inch long 1/4 wave
stub antenna inside the can. It helps if the end of the brass tube is
first filed a little to form a rounded edge. Bind the cable tightly to
the brass tube with a few turns of .025 lock wire, fish line or
whatever, and weatherproof it with some RTV silicon. The PC end
requires a connector to match, usually reverse SMA on a pigtail. I
made my connector from a brass nut tapped out to 1/4 by 32 with
another 3/8 brass tube soldered to it and a centre pin from a
sacrificed DB-9 connector. Its installed on the PC cable end same as
antenna end and screws onto the reverse SMA socket on the Wireless
card. No expensive "N" connectors or exotic coax. Ensure the two
antenna polarizations (ie vertical or horizontal) are matched by
rotating one can for best signal. You may also want to experiment with
different stub antenna spacing from the closed end of the can however
its not highly critical and 2.5 inch works well for me. This post was
sent through it. Good luck.

Jeff Liebermann wrote:

> On Sat, 06 Aug 2005 19:26:18 GMT, Tony Hwang <(E-Mail Removed)> wrote:
>
>
>>Yagi (Yagi Uda) antenna is gain antenna. The more element, the more
>>gain. Higher gain means narrower beam of angle and higher F/B ratio.
>
>
> 50% wrong. The higher the gain, the narrower the beamwidth for a
> given class of antenna. Different types of antennas have different
> beamwidths for identical gain antenna.
>
> -3dB beamwidth for different gain yagi antennas:
> gain -3db beamwidth
> dBi degrees
> 8 60
> 10 40
> 14 30
> 16 25
>
> -3dB beamwidth for different types of antennas of roughly the same
> gain:
> Type gain -3dB Beamwidth
> dBI degress
> patch 13 38
> yagi 14 30
> planar 13 25
> dish 15 19
>
> Note that at 200 yards, even the narrowest antenna (dish) will still
> have a wide enough beamwidth to avoid alignment problems.
>
> The front to back ratio (f/b) and sidelobes are a function of the
> design of the antenna and has little to do with the gain. It is
> possible to trade f/b ratio for gain on most antennas and optimize for
> one or the other. However, higher gain antennas do not automatically
> imply a higher f/b ratio. Actually, it's quite the opposite as high
> gain yagi's tend to leak more than low gain yagi's.
>
>
>>You'll have to experiment setting up from both ends for best signal
>>strength. Think LOS(ling of sight). Radio wave LOS is not as straight as
>>visual LOS tho.
>
>
> Line of sight is ALWAYS a straight line. No curvature involved,
> especially at 200 yards. I think you're thinking about Fresnel Zone
> clearance, which requires more unobstructed clearance at midpoint than
> visual clearance. At 2.4Ghz and 200 yards, the midpoint Fresnel zone
> clearance for one zone is 7.8ft radius. However, that's academic as
> the trees will probably cause more problems than the lack of Fresnel
> zone clearance.
>
>
Hi,
What is different? Higher gain = more element = narrower beam angle.
Used work in microwave, troposcatter, sattelite comm systems when I was
young.
Talking from experience with plain language. Want to go in detail in
antenna theory? Then please do via email direct.
Tony, VE6CGX
BSEE, class of '66

Tony Hwang <(E-Mail Removed)> wrote:
>Jeff Liebermann wrote:
>> antennas of roughly the same gain:
>> Type gain -3dB Beamwidth
>> dBI degress
>> patch 13 38
>> yagi 14 30
>> planar 13 25
>> dish 15 19
....

>What is different? Higher gain = more element = narrower beam angle.

But there is also the simple fact that a parabolic dish will
have narrower beamwidth for the same gain, and will have
significantly fewer sidelobes, as a Yagi Uda design.

>Used work in microwave, troposcatter, sattelite comm systems
>when I was young.

Where did you do tropo? That's what I did when I was young.
I did satellite when I was old. And microwave for all of it.

>Talking from experience with plain language. Want to go in
>detail in antenna theory? Then please do via email direct.

Nahhh. Do *not* take it to email. Keep it here, for everyone
now and in the future.

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

On Sun, 07 Aug 2005 16:22:35 GMT, Tony Hwang <(E-Mail Removed)> wrote:

>What is different? Higher gain = more element = narrower beam angle.

What's different is that this is only true for a single class of
antenna such as a yagi. For a given gain, different classes of
antennas (panel, patch, planar, biquad, dish, coffee can, etc) have
different beamwidths.

You also threw the front to back ratio into the puzzle, which has
absolutely nothing to do with the number of elements or the gain.

>Used work in microwave, troposcatter, sattelite comm systems when I was
>young.

I'm 57 and still somewhat young. I used to design, repair, sell, and
install the stuff. Now days, I just fix computers, play consultant,
and answer questions in newsgroups.

>Talking from experience with plain language.

You call this plain language?
"Think LOS(ling of sight). Radio wave LOS is not as straight as
visual LOS tho."
It's just plain wrong. Microwave line of sight is a straight line
unless you want to play over the horizon, ducting, or knife edge
diffraction. For the distances and frequencies involved in 802.11,
it's a straight line. How will your plain language answer help the
original poster with his antenna selection question?

>Want to go in detail in
>antenna theory? Then please do via email direct.

No thanks. I answer questions in newsgroups and mailing lists for
free. Everyone learns from answers via usenet. Only the people
involved learn from an email exchange. The questions that come via
email, I cosider to be billable consulting. I charge $75/hr and it
typically takes about an hour per question.

>Tony, VE6CGX
>BSEE, class of '66

Jeff, AE6KS (formerly WB6SSY)
BSEE. Cal Poly, Pomona CA 1971.


--
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

Jeff Liebermann wrote:
> On Sun, 07 Aug 2005 16:22:35 GMT, Tony Hwang <(E-Mail Removed)> wrote:
>
>
>>What is different? Higher gain = more element = narrower beam angle.
>
>
> What's different is that this is only true for a single class of
> antenna such as a yagi. For a given gain, different classes of
> antennas (panel, patch, planar, biquad, dish, coffee can, etc) have
> different beamwidths.
>
> You also threw the front to back ratio into the puzzle, which has
> absolutely nothing to do with the number of elements or the gain.
>
>
>>Used work in microwave, troposcatter, sattelite comm systems when I was
>>young.
>
>
> I'm 57 and still somewhat young. I used to design, repair, sell, and
> install the stuff. Now days, I just fix computers, play consultant,
> and answer questions in newsgroups.
>
>
>>Talking from experience with plain language.
>
>
> You call this plain language?
> "Think LOS(ling of sight). Radio wave LOS is not as straight as
> visual LOS tho."
> It's just plain wrong. Microwave line of sight is a straight line
> unless you want to play over the horizon, ducting, or knife edge
> diffraction. For the distances and frequencies involved in 802.11,
> it's a straight line. How will your plain language answer help the
> original poster with his antenna selection question?
>
>
>>Want to go in detail in
>>antenna theory? Then please do via email direct.
>
>
> No thanks. I answer questions in newsgroups and mailing lists for
> free. Everyone learns from answers via usenet. Only the people
> involved learn from an email exchange. The questions that come via
> email, I cosider to be billable consulting. I charge $75/hr and it
> typically takes about an hour per question.
>
>
>>Tony, VE6CGX
>>BSEE, class of '66
>
>
> Jeff, AE6KS (formerly WB6SSY)
> BSEE. Cal Poly, Pomona CA 1971.
>
>
Hi Jeff,
I see you are a Radio Ham over there on the west side. I am too here in
UK and though now not so active, I may have worked you on 20m with my 2
element quad at about 8 mtrs high!
Callsign: G4UYI
Yes I have tried different antennas myself over the years, but now just
stick to a 2mtr vertical for local stuff. I also repair and charge for
my computer services. How times have changed eh?

Cheers

--

Bob H
Leeds UK