Chipset Choice (p2)

Trying to decide between two radio bridges for client mode. Your
opinion?

Both radios are from same vendor.

Model X has conexant / intersil Prism 2.5 chipset but has had occasional
firmware and other complaints from users. Said by one company rep. to be
better in range than model Y. 200mw transmit output, 95dBm receive at
1Mbs

Model Y has Realtek RTL8186 SoC chipset and is new to market, firmware
either new or recently revised. 400mw transmit power, 92dBm receive at
1Mbs.

Both have 8dbi integrated panel antennas 35 degree horizontal and
vertical spread.

My main AP is 2/5 mile away, near line of sight, 90 degrees to the side
of the primary vector of the signal which is pointed in a downward tilt
to cover an immediate two block area. My line of sight window is about
45 degrees vertical by 100 degrees horizontal, so my guess is I am
capturing only the portion of the signal at right angle to it and within
that window. Several other AP choices at further distance to be
determined if I ever get it mast mounted with a rotator.

So far I have had to forget an 85mw radio that could only get a stable
connection about 20% of the time with a small whip antenna (5dbi?), due
my guess to some waving tree branches that partly obstruct.

What is your best guess as to which model, X or Y I should try next? In
talking to one mfg. rep. he states firmware is better on model Y, but
this is a new model with a fairly new chipset. I also need something
that will be compatible with a wide range of OS's and utility software,
which speaks better for model X (prism). What do you think?

JDavidson <(E-Mail Removed)> hath wroth:

>Trying to decide between two radio bridges for client mode. Your
>opinion?
>
>Both radios are from same vendor.
>
>Model X has conexant / intersil Prism 2.5 chipset but has had occasional
>firmware and other complaints from users. Said by one company rep. to be
>better in range than model Y. 200mw transmit output, 95dBm receive at
>1Mbs
>
>Model Y has Realtek RTL8186 SoC chipset and is new to market, firmware
>either new or recently revised. 400mw transmit power, 92dBm receive at
>1Mbs.
>
>Both have 8dbi integrated panel antennas 35 degree horizontal and
>vertical spread.
>
>My main AP is 2/5 mile away, near line of sight, 90 degrees to the side
>of the primary vector of the signal which is pointed in a downward tilt
>to cover an immediate two block area. My line of sight window is about
>45 degrees vertical by 100 degrees horizontal, so my guess is I am
>capturing only the portion of the signal at right angle to it and within
>that window. Several other AP choices at further distance to be
>determined if I ever get it mast mounted with a rotator.
>
>So far I have had to forget an 85mw radio that could only get a stable
>connection about 20% of the time with a small whip antenna (5dbi?), due
>my guess to some waving tree branches that partly obstruct.
>
>What is your best guess as to which model, X or Y I should try next? In
>talking to one mfg. rep. he states firmware is better on model Y, but
>this is a new model with a fairly new chipset. I also need something
>that will be compatible with a wide range of OS's and utility software,
>which speaks better for model X (prism). What do you think?

I'm not going to offer any opinions on the quality of the devices
without knowing the names and models. However, I can offer some clues
as to whether your antenna scheme is going to work. Methinks not.

An 8dBi panel antenna has a -3dB beamwidth of about 60 degrees. At 90
degrees from the center line, the pattern appears to be about -40dB
down. That might work if your coverage area was close enough.

I can't decode what you're doing. I have no idea what a "main AP" is
or what manner of hardware it implied. I don't even know what the
selection of bridge radios has to do with this AP. Is this a seperate
question or part of the bridge?

For fun, lets see if 8dBi antennas will even work with your
prospective bridge radios. See the FAQ at:
| http://wireless.wikia.com/wiki/Wi-Fi#Link_Calculations
Plugging in numbers for the Model X bridge, I get:
TX power = +23 dBm
TX coax loss = 1 dB (mostly internal connectors)
TX ant gain = 8dBi
Distance = 0.4 miles
RX ant gain = 8dBi
RX coax loss = 1 dBi
RX sens = -95 dBm (at 1 Mbits/sec)
Fade margin = unknown
Plugging into:
http://www.terabeam.com/support/calculations/som.php
I get a fade margin of 35.8dB. No problem as anything over 20dB fade
margin will work well.

If you really only want 1Mbit/sec connection for about a 300kbit/sec
thruput, you can have it. Incidentally, I believe the -95dBm
sensitivity at 1Mbit/sec is baloney. It should be around -89dBm.

I think you'll find that higher speeds are more useful. Using my
numbers from the above URL (because you didn't specify the maker and
model so I can't look them up), the fastest connection speed possible,
for a 20dB fade margin, will be about 24 Mbits/sec for a thruput of
about 12 Mbits/sec. Good enough.

Run the numbers yourself for Model Y for practice.

Please note that the above calculations are the best case. It only
gets worse. You casually mumbled something about tree branches waving
in the wind, which implies that you have a tree in the way. I suggest
you calculate your Fresnel Zone at:
http://www.terabeam.com/support/calc...esnel-zone.php
You should have 0.8*Fresnel zone clearance at midpoint. For 0.4
miles, you need a 12 foot radius about the center line clearance,
which includes trees, buildings, and the ground.

Incidentally, the stock rubber ducky is not 5dBi gain. It's about
2dBi at best.
--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann <(E-Mail Removed)> hath wroth:

>JDavidson <(E-Mail Removed)> hath wroth:
>
>>Trying to decide between two radio bridges for client mode. Your
>>opinion?
>>
>>Both radios are from same vendor.

Oh, you're using the bridge radios as client radios. I thought you
were building a point to point bridge with two of them. That make my
point to point link cals kinda worthless. Substitute the real numbers
for your access point and try again. However, since you're well
outside the major lobe of the antenna on one end, the antenna gain
should be from the pattern graphs for your angle of depression. That's
going to be far less than the maximum antenna gain.

Incidentally, I have the same problem at home. I live on the side of
a hill. The clients are all downhill from me at about -45 degrees. I
have to use multiple antennas to cover them all.

My points about the fresnel zone still apply.

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

I sent you a detailed answer to your previous to this reply, but it was
either cancelled or does not appear on my servers, so you probably did
not receive it; not sure you'll get this one either.

When you are trying to receive an AP signal approx 70-90 degrees off
it's central vector (straight ahead from a sector antenna), is there a
method for estimating the amount of signal strength loss when using a
panel antenna to receive? Can you give a simplified explaination of how
this is done using those antenna signal spread graphs I see all the
time?

Also, once these outdoor radios are on a mast, if they screw up and you
have to reset them, then you must have remote reset, or else you have to
climb the pole so to speak?

Jeff Liebermann <(E-Mail Removed)> wrote in
news:(E-Mail Removed):

> Jeff Liebermann <(E-Mail Removed)> hath wroth:
>
>>JDavidson <(E-Mail Removed)> hath wroth:
>>
>>>Trying to decide between two radio bridges for client mode. Your
>>>opinion?
>>>
>>>Both radios are from same vendor.
>
> Oh, you're using the bridge radios as client radios. I thought you
> were building a point to point bridge with two of them. That make my
> point to point link cals kinda worthless. Substitute the real numbers
> for your access point and try again. However, since you're well
> outside the major lobe of the antenna on one end, the antenna gain
> should be from the pattern graphs for your angle of depression. That's
> going to be far less than the maximum antenna gain.
>
> Incidentally, I have the same problem at home. I live on the side of
> a hill. The clients are all downhill from me at about -45 degrees. I
> have to use multiple antennas to cover them all.
>
> My points about the fresnel zone still apply.
>

JDavidson <(E-Mail Removed)> hath wroth:

>I sent you a detailed answer to your previous to this reply, but it was
>either cancelled or does not appear on my servers, so you probably did
>not receive it; not sure you'll get this one either.

Nothing appeared on the sbcglobal.net and newsguy.com. I can check
others but those are the one's I read.

>When you are trying to receive an AP signal approx 70-90 degrees off
>it's central vector (straight ahead from a sector antenna), is there a
>method for estimating the amount of signal strength loss when using a
>panel antenna to receive?

Very easy. Let's take a typcial real sector antenna pattern:
http://www.superpass.com/SPDG16T2.html
This is a 2.4GHz 120 degree 12.2dBi gain. Horizontal pattern is at:
http://www.superpass.com/SPDG16T2.html#V_plane
70 degrees off the center line shows a gain of -5dB below the maximum
gain (outer) circle. Therefore, it has the equivalent of a:
12.2 - 5 = 7.2dBi
gain. Similarly, at 90 degrees off axis, the gain is -9dB below
maximum or:
12.2 - 9 = 3.2dbi
gain. Incidentally, the 120 degree horizontal beamwidth is based upon
the -3dB points.

>Can you give a simplified explaination of how
>this is done using those antenna signal spread graphs I see all the
>time?

Note that the horizontal gain pattern on this sector antenna is very
different from the vertical gain pattern. It's quite broad on the
horizontal (120 degrees), but very narrow vertically (14 degrees).
That means it won't tolerate much in the way of differences in
elevation between the end points of a link. That's also why sector
antennas and panels usually are mounted with some down-tilt.

>Also, once these outdoor radios are on a mast, if they screw up and you
>have to reset them, then you must have remote reset, or else you have to
>climb the pole so to speak?

Well, the easiest way to do a reset is to cycle the power. Unless you
have a solar powered radio, with a gel battery on top of the pole, you
should have access to the power source, especially with PoE. It
should be easy to power cycle one of those.

If the radio is remotely located, a drive to the mountain radio site
is no fun, especially in winter. I have a few pager receivers and
VHF/UHF radios setup to trigger a relay or solid state switch to cycle
the power on mountain top installs. Of course, the one and only
remote weather station where I do NOT have a remote reset system is
the one than seems to hang once a week. Grrrrr....



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

Thanks much, Jeff. I am glad your on this group. The post musta been
cancelled by some rogue A**hole. It appeared and then disappeared, even
from the server it was posted to. I have a pretty good idea what I'm up
against now, thanks to you. I will post later if I get stuck.

Jeff Liebermann <(E-Mail Removed)> wrote in
news:(E-Mail Removed):

> JDavidson <(E-Mail Removed)> hath wroth:
>
>>I sent you a detailed answer to your previous to this reply, but it
>>was either cancelled or does not appear on my servers, so you probably
>>did not receive it; not sure you'll get this one either.
>
> Nothing appeared on the sbcglobal.net and newsguy.com. I can check
> others but those are the one's I read.
>
>>When you are trying to receive an AP signal approx 70-90 degrees off
>>it's central vector (straight ahead from a sector antenna), is there a
>>method for estimating the amount of signal strength loss when using a
>>panel antenna to receive?
>
> Very easy. Let's take a typcial real sector antenna pattern:
> http://www.superpass.com/SPDG16T2.html
> This is a 2.4GHz 120 degree 12.2dBi gain. Horizontal pattern is at:
> http://www.superpass.com/SPDG16T2.html#V_plane
> 70 degrees off the center line shows a gain of -5dB below the maximum
> gain (outer) circle. Therefore, it has the equivalent of a:
> 12.2 - 5 = 7.2dBi
> gain. Similarly, at 90 degrees off axis, the gain is -9dB below
> maximum or:
> 12.2 - 9 = 3.2dbi
> gain. Incidentally, the 120 degree horizontal beamwidth is based upon
> the -3dB points.
>
>>Can you give a simplified explaination of how
>>this is done using those antenna signal spread graphs I see all the
>>time?
>
> Note that the horizontal gain pattern on this sector antenna is very
> different from the vertical gain pattern. It's quite broad on the
> horizontal (120 degrees), but very narrow vertically (14 degrees).
> That means it won't tolerate much in the way of differences in
> elevation between the end points of a link. That's also why sector
> antennas and panels usually are mounted with some down-tilt.
>
>>Also, once these outdoor radios are on a mast, if they screw up and
>>you have to reset them, then you must have remote reset, or else you
>>have to climb the pole so to speak?
>
> Well, the easiest way to do a reset is to cycle the power. Unless you
> have a solar powered radio, with a gel battery on top of the pole, you
> should have access to the power source, especially with PoE. It
> should be easy to power cycle one of those.
>
> If the radio is remotely located, a drive to the mountain radio site
> is no fun, especially in winter. I have a few pager receivers and
> VHF/UHF radios setup to trigger a relay or solid state switch to cycle
> the power on mountain top installs. Of course, the one and only
> remote weather station where I do NOT have a remote reset system is
> the one than seems to hang once a week. Grrrrr....
>
>
>

On Fri, 7 Jul 2006 19:20:36 +0000 (UTC), JDavidson <(E-Mail Removed)>
wrote in <e8mc63$1j6$(E-Mail Removed)>:

>... The post musta been
>cancelled by some rogue A**hole. It appeared and then disappeared, even
>from the server it was posted to. ...

I very much doubt that -- most newservers don't honor cancels, and it
doesn't appear on any of the major services. More likely some issue or
problem with your news provider. Usenet propagation is far from perfect
-- a small but significant percentage of posts simply get lost.

--
Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_How_To>
Fixes to Wi-Fi Problems: <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>

JDavidson <(E-Mail Removed)> hath wroth:

>Thanks much, Jeff. I am glad your on this group. The post musta been
>cancelled by some rogue A**hole. It appeared and then disappeared, even
>from the server it was posted to. I have a pretty good idea what I'm up
>against now, thanks to you. I will post later if I get stuck.

Nope. It's not a cancelbot. You're apparently posting through
aioe.org which declares it's policy on control messages as:
http://news.aioe.org/article.php3?id_article=17#d9
Aioe.org server doesn’t accept neither Control Messages
nor Cancel Requests.

As John memtioned, some news messages simply disappear. I switch back
an forth between Newsguy and SBCglobal.net news servers. It's not
unusual for me to see messages on one, that don't appear on the other.
It's also not unusual to have a few messages magically appear many
days after they were posted. Also, some of my postings have
disappeared, only to be listed as spam by Newsguy.

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