Hy all.
I have a 3W amplifier (802.11b) buyied from HyperlinkTech (USA), and I want to make a public hotspot with a RB112. The problem is: what mPCI should I use? Which is the best for my use? Consider that I have 12m Aircom Plus (-3dB approx) from the RB112 to a omnidirectional antenna, and I'd like to try the 802.11g mode (no 802.11a, absolutely), so I need a powerful mPCI (with 802.11g I can't use my amplifier).
Which can I use? I can easily buy one of these cards:

- WLM54G23 / High Power Atheros 23dBm 802.11b/g
- CM9 / Wistron Neweb Atheros 802.11a/b/g
- SR2-80211bg / Ubiquiti Super Range 2 400mw 802.11b/g
- NMP-8602 / Senao Atheros High Power 26dbm
- NL2511MP / Senao Prism 2.5 802.11b 200mW

I think (from technical detail) that the Ubiquiti SR2 is the best choice for me, but I'd like to have an impression from REAL user as I know I can find on this forum.

Thanks

73 de IZ3HAD

loose the amp it will cause issues..

and DO NOT get a NMP-8602 for laptop clients..\

I suggest a sr2 + A horiz. Pol. Antenna.

loose the amp it will cause issues..

and DO NOT get a NMP-8602 for laptop clients..\

I suggest a sr2 + A horiz. Pol. Antenna.

do not use the AMP,

I have used

- NMP-8602 / Senao Atheros ETSI Version
- NL2511MP / Senao Prism 2.5 802.11b 200mW

and found both to be good cards although the NL2511MP will not do WDS.

Choosing the right antenna is critical for creating a good hotspot. The last one we built was in a small country hotel using a RB532 in metal case and 2 MikroTik plastic antennas connected to a single NMP-8602 ETSI. It works great!

DO NOT get a NMP-8602 for laptop clients

The client has a Linksys WRT54GL and a VAGI 16dBi antenna. But, can you explain why can't install NMP-8602 on a laptop? High power consumption? Other?

I suggest a sr2 + A horiz. Pol. Antenna.

Have you tested a SR2? Do it works well?

ah..i thought you were trying to serve wifi laptop customers like at a hotel or something...

in the case above i suggest using an sr2 as i used to have quite a few weird issues on the client side with 8602...they are very suspectable to noise....i had a 8602 serving wifi clients and every time the 2.4ghz cordless phone would right, all users would get disconnected and not come back for a minute or two or more... trying another 8602 did not help....put in a sr2, no issues!

if you are doing PtP then the 8602 should be good, just look for some specific posts from ppl who have experience with that linksys unit on the client side.

eiter way i have always found the SR2 to be better than the 8602...but you pay almost twice as much

if you are doing PtP then the 8602 should be good, just look for some specific posts from ppl who have experience with that linksys unit on the client side.

I have a lot of experience on Linksys WRT54G/GS/GL unit. The only remain thing was the choice of the mPCI card that will serve this PtMP link (ALL client are static and WRT54G/GL unit). I asked info on SR2 because I readed somewhere on this forum that these mPCI aren't as good as declared on the receive section.

eiter way i have always found the SR2 to be better than the 8602...but you pay almost twice as much

Yes, I know it.

SR2 without AMP.... the best choice...

Regards

NMP-8602 / Senao Atheros High Power 26dbm (( dont think about it the worest card ever i tried very veyr veyr veery very very very bad cardddd))

i think in your case the AMP is the best

example :


we are doing small village with 1 watt amp with regular AP (hyperlink omni 15 db)
client is connected and browsing from normal toshiba laptop the AP @ ditance 10km we reach (clear line of sight)


with senao max we got 1.2 km (with disconnection also)


@ 700 meter we doing a test

SNR we got in laptop side 5 db with the AP+ amp we got 27 db


anyway i have 3 mpci senao new im ready to replace it with 1 SR2 if anyone accept

thanks

SR2 without AMP.... the best choice...

Regards

yes, i agree. this is the best choise.

regards,
C. G.

Not to mention you run into major legal issues with a 3 watt amp...

SR2 without the amp is the best.

Not to mention you run into major legal issues with a 3 watt amp...

My limit is 500W EIRP (I'm an OM )

73 de IZ3HAD

What antenna are you using?

Omnidirectional, 12dBi.

SR2 - no amp is best solution.

If you use amp, users will have strong signal, but noise will be enormous and surfing will be worst then on dial-up.

Why?
Answer is simple, you will hit your clients with 3W and they will have great RX , but their TX will be killed...

I'm sorry but you just spent your money on amp for nothing...

Just my 2 cents...

Cheers all...

If you use amp, users will have strong signal, but noise will be enormous and surfing will be worst then on dial-up.

The amplifier is directly connected to the mPCI (20cm pigtail), so I don't think the noise are too great...

Answer is simple, you will hit your clients with 3W and they will have great RX , but their TX will be killed...

Why their TX are killed? In 802.11a/b/g the access method to the layer 2 is CSMA/CA, so, when someone "speak", all other listen only.
But, if you are convinced, can you explain to me why the TX of a GSM base station is much more greater than a GSM mobile? It's not seem to be a bad quality on voice call, and they using amp!

I think that nobody in this forum has seen a setup where an Amp has improved the conditions. Only the opposite. At least that's what I think after reading this forum for more than a year

Normis, I'll take yours (and other user too) suggestions in great consideration. I don't want to start a flame, becouse my final intention is to setting up my hotspot without the amplifier. On my first post I wrote:

and I'd like to try the 802.11g mode (no 802.11a, absolutely), so I need a powerful mPCI (with 802.11g I can't use my amplifier)

.
Thanks to all.

73 de IZ3HAD

R52, SR2 and CM9 are all very good cards.

I'm waiting for a CM9 (I buyed it becouse SR2 was out of stock when I made the order on my dealer). I'll use it with the amplifier (spec says 802.11g/54Mbps at 13dBm, and with 3dBm attenuation for cable + connectors loss + 12dBi antenna I will give only 22dBm EIRP) until the SR2 will be available again on my dealer. I made a 3-days test with R52+amp, "b only" mode, and the link was up and running with no problem at all, then, I gave back R52 to my friend.
In any case, I'll wrote again on this thread with updated info on CM9/SR2 with and without 3W amp.

Again, thanks to all.

I have seen small improvements in keeping customers connected with poor signals with the slight loss of throughput using amps but never used a 3 watt amp?

I normally look at it as that if your using an omni as base station the recieved signal to the client will be less than the recieved signal from a client with directional antenna. I used to use a 500mw amp to improve this situation and it does seem to improve things but with the dirtier signal you will lose some bandwidth.

Sr2 400mw to 12db omni to clients using 100mw 15db yagi seems to give best throughput and certainly better than an amp. It's also nice and balanced. I have to say 3w is pretty pointless if clients are using normal 80 - 100mw hardware. If you have a 3w client I would be interested to see how good the range was on that

I have seen small improvements in keeping customers connected with poor signals with the slight loss of throughput using amps

A loss, like you see is due to signal saturation of the G/A modulation and over pre-amplification rx gain.

In order to use a bi-directional amplifier (BDA) with -no- degrading effects, several things have to be understood.....

If the amp does not have some automatic power control that interactively looks at the linearity of the signal, you'll need to adjust your radio's output accordingly. Any compression of the signal will result in any of the QAM based modulations simply not working correctly. You'll fall back to QPSK most of the time, which is more forgiving of non-linearity, but you fall back to 18Mb/sec. You have to keep the signal down 6dB from the amp's compression point to not have throughput issues. This generally means a 1 watt amp is only good for 250mW. Some auto power control amps also use a quadratic averaging scheme for looking at the signal for max TX power, and this algorithm, which i've shown clearly on my Anritsu analyzer, is way to slow to reacting to changes and will also cause problems with the signal as well.

The second issue is the type of pre-amp used in the BDA. Some use really cheap MMIC components that have 3dB and higher noise figures, and some more don't have any front end filtering to keep out of band receive gain from occurring . What's worse is a amp that has say 17dB of gain on the receive, that's way to hot. A well built BDA will use PHEMT based pre-amplification, with at least a 3 pole ceramic filter on the receive path (6 preferably). The two combined will only end up giving you a real world 10-12dB of receive gain, but at that point, it's not running the radio's receiver over with too much signal or noise, and it's only amplifying what you want it to.


That being said, I fully agree that going with a higher power radio with a higher gain more directional antenna is going to be your best bet for the lion share of applications.


I don't agree with a blanket statement of amps not working at all. Having designed several models of BDA's, I can say with 100% certainty that my points made here are the bulk of the issues. The big problem is that alot of amps truely don't work well or have horrible components in them. Finally most of the installs i've seen and consulted on with amps are being driven into compression, which truely will make things worse. A simple look with a analyzer shows this, and you can drop the tx power of the radio till it clears, then wha-la, things work better then. Problem is most installers don't carry a $20,000 analzyer with them to look at this.


On to the question that started this thread....


Being a Radio Amateur operator as I am here in the US, I run a network of data nodes that link our voice repeaters together over some very long distances, and we're not limited to the same power limitations as normal users are by part 97 FCC rules, so my nodes are running 5 watt BDA's on 802.11A links, but again, to keep compression from occuring, i'm only driving the amps with enough power to just stay under the compression point, with ends up derating the amplifier to only about 1.5 watts, but 1.5watts into a 32dB antenna is still -ALOT- of power. I am using the R52 cards with amps and have spectrum analyzer plots if you would like to see them showing the linearity of the the signal. The R52 is also good for amateur radio use as you can take advantage or portions of the spectrum we're licensed to use.


Seeya,
Dave
KG4YZY

http://www.fab-corp.com
http://www.aprsfl.net

Being a Radio Amateur operator as I am here in the US

Yes, I'm already a Radio Amateur (IZ3HAD).

I run a network of data nodes that link our voice repeaters together over some very long distances

It's one of our future project.

my nodes are running 5 watt BDA's on 802.11A links

Which type of BDA do you use? Can you provide me some links (with price)?

but 1.5watts into a 32dB antenna is still -ALOT- of power

Yes, i know it!

I am using the R52 cards with amps and have spectrum analyzer plots if you would like to see them showing the linearity of the the signal.

Yes, I'd linke to see it. Can you post it on this thread?
Thanks

73 de IZ3HAD