Accuracy of signal strength in Netstumbler/ AP

andrejun · 05-10-2004

Should I believe the readings from Netstumbler or the AP??????

As some of you guys know I am working on a 3.1 mile link.
We have peaked the Dishes atop towers with a notebook running Netstumbler, a WiFi card connected to a pigtail, an N coupler, through an N->RPSMA pigtail, which was then connected to the antenna. We then got displayed signal strength of -71~ -69 dbm, however we could not connect to the remote AP on the note book. Apparently indicating a signal below the receive threshold. Using the Ap's (which are connected directly to the dish via included 24" coax, so much less cable loss, we have intermittent packet loss (about 75% of packets make it) we are set to run B only, 1 mbit. When we bump it up to 2 mbit we loose connection (basically entirely) According to Netgears documentation we need -93 dbm for 1 mbit, -92 for 2 mbit, -92 for 5.5 mbit and -89 for 11 mbit, so according to our Netstumbler readings (which had WAY WAY more cable loss) we should be easily getting a 11 mbit connection, however we are obviously stuck someplace in between the receive threshold for 1 mbit and the receive threshold for 2 mbit (according to Netgear -93 or so). So is Netstumbler miss-representing the signal strength or is Netgear miss-representing their product

Thorn · 05-10-2004

If the card is an ORiNOCO, then I'd believe it. If the you're using a card with an NDIS driver then it's probably questionable.

Having said that, are the other factors set up properly? Frensel Zone, etc.?

By the way, is there any chance of you using punctuation? That was damned hard to read.

andrejun · 05-11-2004

Thanks Thorn.

Sorry about the grammar, it's not my strength esp. while tired.

I do have an Orinoco, however my tower guy (friend @ other end) wanted to use another card which he bought which has 300 mw output, I wasn't really to worried about transmit power @ the time just receive. I really really want to use my Orinoco, I'll see if I can convince him.

Edit:
We are @ approx 60% Fresnel, on super flat terrain (Scott is where the west begins so we are on the beginnings of the prairie). However we have a pine tree directly in line of site @ my friends house approx 20 feet from his tower, I really think this is affecting or connection in a big way. I have an Oak tree within what I'd say 10 feet of the line of site path, but it's not the trunk like what we have on the other end, I may trim a few branches on this end as well.

The Others · 05-11-2004

Quote:

Originally Posted by andrejun

I do have an Orinoco, however my tower guy (friend @ other end) wanted to use another card which he bought which has 300 mw output, I wasn't really to worried about transmit power @ the time just receive. I really really want to use my Orinoco, I'll see if I can convince him.

I'd do it again with the orinoco card. Get the antenna lined up and bolt it in place, then swap the cards. Bingo.

Thorn · 05-11-2004

Quote:

Originally Posted by andrejun

Thanks Thorn.

Sorry about the grammar, it's not my strength esp. while tired.

I do have an Orinoco, however my tower guy (friend @ other end) wanted to use another card which he bought which has 300 mw output, I wasn't really to worried about transmit power @ the time just receive. I really really want to use my Orinoco, I'll see if I can convince him.

If you do use an ORiNOCO at both ends you should be fairly confident of link RF levels. In my experience it's always been very close.

If the signals are what you expect, but you're still experiencing packet loss, then you should check for FZ, other possible interference, antenna polarity, etc. Make sure the path is what you're expecting. If possible, you might even want to visually check the link at the antenna level for anything unexpected, such as power lines. I know of one person having set up such a link, found that there was a 19kv high-voltage line right in the path. It was twisting the signal about 45º out of phase. He was able to get a high RSSI, but the packet loss was high, until he canted his antenna over.

andrejun · 05-12-2004

Thanks again guys.
It looks like the wetter it is the better it works, in pouring rain we get 95% + packets in the calm after the storm we get 85% and in dry we get 50% with dew (midnight on) we get about 75%.

Any ideas?

I'm thinking the moisture is allowing for a multi path.

Thorn · 05-12-2004

Mulitpath is a good bet.

Looking at your above edit, I'd say the real problem is that pine tree. Time for a chain saw. A 60% FZ isn't great, but it is usable, but the pine is a big problem.

andrejun · 05-16-2004

Just cut the pine tree, we have much much better pings, howver our thoroughput is still pretty poor, I think we need to re-peak now that the tree is not blocking/ bending the signal.

andrejun · 05-24-2004

Well guys we Re-peaked and got about -56dbi which I consider to be pretty decent.

However we are still getting poor performance like 111.2 kilobits per second. We can set our speed to whatever we want now and speed is not affected. The only thing affected is that the higher we set it, the better the ping times get.

When peaking we could not get a wireless card to associate with the remote access point so I'd assume we have a signal quality issue.

I did a little scientific survey of the oak tree, and discovered that it is much taller than I thought. We are actually going strait through an awful lot of the tree. Cutting that much of the tree is not an option so it looks like I will be re-locating my tower (guyed pole) or building a real tower, if I can acquire some sections @ a reasonable price.

The only question that I have is is there any way of improving signal quality short of removing objects from line of site? I seriously doubt it, but I just have to ask.

05-10-2004	#1 (permalink)
andrejun Registered Member Join Date: Dec 2002 Posts: 34	Accuracy of signal strength in Netstumbler/ AP Should I believe the readings from Netstumbler or the AP?????? As some of you guys know I am working on a 3.1 mile link. We have peaked the Dishes atop towers with a notebook running Netstumbler, a WiFi card connected to a pigtail, an N coupler, through an N->RPSMA pigtail, which was then connected to the antenna. We then got displayed signal strength of -71~ -69 dbm, however we could not connect to the remote AP on the note book. Apparently indicating a signal below the receive threshold. Using the Ap's (which are connected directly to the dish via included 24" coax, so much less cable loss, we have intermittent packet loss (about 75% of packets make it) we are set to run B only, 1 mbit. When we bump it up to 2 mbit we loose connection (basically entirely) According to Netgears documentation we need -93 dbm for 1 mbit, -92 for 2 mbit, -92 for 5.5 mbit and -89 for 11 mbit, so according to our Netstumbler readings (which had WAY WAY more cable loss) we should be easily getting a 11 mbit connection, however we are obviously stuck someplace in between the receive threshold for 1 mbit and the receive threshold for 2 mbit (according to Netgear -93 or so). So is Netstumbler miss-representing the signal strength or is Netgear miss-representing their product __________________ 87 Supra with 15" tft on dash 1ghz supra pc in trunk and orinoco silver on tap. Last edited by andrejun : 05-11-2004 at 07:18 AM.

05-10-2004	#2 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,358	If the card is an ORiNOCO, then I'd believe it. If the you're using a card with an NDIS driver then it's probably questionable. Having said that, are the other factors set up properly? Frensel Zone, etc.? By the way, is there any chance of you using punctuation? That was damned hard to read. __________________ Thorn "Read Altas Shrugged. Compare it to today. Repeat as necessary"

05-11-2004	#3 (permalink)
andrejun Registered Member Join Date: Dec 2002 Posts: 34	Thanks Thorn. Sorry about the grammar, it's not my strength esp. while tired. I do have an Orinoco, however my tower guy (friend @ other end) wanted to use another card which he bought which has 300 mw output, I wasn't really to worried about transmit power @ the time just receive. I really really want to use my Orinoco, I'll see if I can convince him. Edit: We are @ approx 60% Fresnel, on super flat terrain (Scott is where the west begins so we are on the beginnings of the prairie). However we have a pine tree directly in line of site @ my friends house approx 20 feet from his tower, I really think this is affecting or connection in a big way. I have an Oak tree within what I'd say 10 feet of the line of site path, but it's not the trunk like what we have on the other end, I may trim a few branches on this end as well. __________________ 87 Supra with 15" tft on dash 1ghz supra pc in trunk and orinoco silver on tap. Last edited by andrejun : 05-11-2004 at 07:31 AM.

05-12-2004	#6 (permalink)
andrejun Registered Member Join Date: Dec 2002 Posts: 34	Thanks again guys. It looks like the wetter it is the better it works, in pouring rain we get 95% + packets in the calm after the storm we get 85% and in dry we get 50% with dew (midnight on) we get about 75%. Any ideas? I'm thinking the moisture is allowing for a multi path. __________________ 87 Supra with 15" tft on dash 1ghz supra pc in trunk and orinoco silver on tap.

05-12-2004	#7 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,358	Mulitpath is a good bet. Looking at your above edit, I'd say the real problem is that pine tree. Time for a chain saw. A 60% FZ isn't great, but it is usable, but the pine is a big problem. __________________ Thorn "Read Altas Shrugged. Compare it to today. Repeat as necessary"

05-16-2004	#8 (permalink)
andrejun Registered Member Join Date: Dec 2002 Posts: 34	Just cut the pine tree, we have much much better pings, howver our thoroughput is still pretty poor, I think we need to re-peak now that the tree is not blocking/ bending the signal. __________________ 87 Supra with 15" tft on dash 1ghz supra pc in trunk and orinoco silver on tap.

05-24-2004	#9 (permalink)
andrejun Registered Member Join Date: Dec 2002 Posts: 34	Well guys we Re-peaked and got about -56dbi which I consider to be pretty decent. However we are still getting poor performance like 111.2 kilobits per second. We can set our speed to whatever we want now and speed is not affected. The only thing affected is that the higher we set it, the better the ping times get. When peaking we could not get a wireless card to associate with the remote access point so I'd assume we have a signal quality issue. I did a little scientific survey of the oak tree, and discovered that it is much taller than I thought. We are actually going strait through an awful lot of the tree. Cutting that much of the tree is not an option so it looks like I will be re-locating my tower (guyed pole) or building a real tower, if I can acquire some sections @ a reasonable price. The only question that I have is is there any way of improving signal quality short of removing objects from line of site? I seriously doubt it, but I just have to ask. __________________ 87 Supra with 15" tft on dash 1ghz supra pc in trunk and orinoco silver on tap.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode