Info needed on possible factors affecting signal range

Hello all

I've operated a wireless network at home for a couple of years now and never needed this group up until now, so please forgive me if I'm asking questions that are common knowledge (I have already checked out Google groups for possible answers, but with no success).

Anyway, the issue is this:

I was able to implement an SMC Barricade (SMC7004AWBR) with an unencrypted

802.11b WLAN from the top shelf in an upstairs room at the front of my house, and was able to get a strong enough signal in the back garden on a Dell laptop with a Belkin PC card (F5D6020u). Proof of concept achieved, I've not bothered using it in the garden since then.

In the meantime I temporarily retired said laptop/PC card and implemented

128 bit security on the WLAN. I've also added in an Ethernet network drive, which is connected to the Barricade but sits on the shelf below it.

Now that I've started using the WLAN in earnest again I've noticed that I'm getting a poorer link quality, and am having trouble maintaining a link in the room almost directly underneath the router. In fact, the Dell laptop/PC card combo signal strength indicator leaps around all over the place from "Excellent" to "Not Connected" even when it is in the same room as the router (a second laptop, an HP with built-in WLAN capability is ok).

Is encryption giving a poorer signal, or is the presence of another electronic device that is causing problems? Or is it both? Can my particular wireless router have its antenna upgraded to solve this problem? Is there anything else I can do? Physics isn't my strong point - I just want things to work!

Reply to
Martin Lowe
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Did you buy some new cordless phones, or a video sender, or a new microwave? The first two use the same frequency as 802.11b/g, the latter generates interference.

Mark McIntyre

Reply to
Mark McIntyre

The OP is in the UK and DECT phones work from 1.88Ghz to 1.9Ghz so shouldn't cause interference.

Bob

Reply to
Bob II

Mark McIntyre wrote in news: snipped-for-privacy@4ax.com:

The latter also operates in the 2.4Ghz range, which is why it would cause interference. A leaky microwave that is. That is the resonant frequency of water, which is how the microwave operates, and why trees full of leaves absorb 2.4 GHz frequencies.

I've actually seen a few article's about using the magnetron from a microwave oven to build hi power amplifier's.

Reply to
DanS

Got any cites? A magnetron is a power oscillator - there is a power source, a magnetic field, and one RF terminal (coax or waveguide depending on frequency range). There is a an amplifier based on the same principles as the magnetron, called a "Crossed-Field Amplifier", but they are comparatively rare, and of limited usefulness (they are limited in gain to about 15 dB because of feedback, and are quite noisy and very limited in bandwidth). They are a saturated gain device, meaning the power out is relatively independent of (RF) power in. Their advantages are a relatively high DC to RF efficiency (60% is practical), and they can be designed for _very_ high peak power. Converting a magnetron to act as an amplifier would be an interesting exercise, given that you'd have to open the tube and install an RF input connection of some kind, then re-evacuate the tube and seal it. Try a google search for the word "amplitron" which is a trademark for CFAs from Raytheon (the company that "invented" the microwave oven).

Old guy

Reply to
Moe Trin

Hi Mark

The only device we have from those you mentioned is a cordless phone. I've unplugged it and tested connection and found no difference (in fact, the laptop now can't connect!)

One thing I didn't mention before that springs to mind is that I'm pretty sure I was the first to use a WLAN in my street - I only encrypted it when I later found that there were two others (one is secure, the other isn't).

Reply to
Martin Lowe

Download netstumbler or similar, install it on the lappy, and do a site survey. You will hopefully see the your own as well as any other WLANs and their setups (channel, encryption etc). This will help you diagnose whether there's interference. Mark McIntyre

Reply to
Mark McIntyre

Hi again

It's allowed me to collect a whole load of data but I'm at a loss as to interpreting it.

What I do see is two 802.11g networks on channel 11 (mine is on channel 6) that are a lot stronger than my network. One is encrypted; the other isn't.

( SSID ) [ SNR Sig Noise ] Flags Channelbits BcnIntvl DataRate LastChannel

( myHouse) [ 147 196 49 ] 11 40 90 110 6 ( linksys ) [ 110 163 53 ] 401 800 100 540 11 ( Applesandpears ) [ 101 154 53 ] 411 800 100 540 11

This is the data summary I get when the laptop is in the same room as the router. The only think that springs to mind is that my 11b network signal is a lot weaker than the two 11g signals. The signal drops off quite dramatically around the house, which it never used to do.

Any further suggestions?

Reply to
Martin Lowe

I find these signal levels quite odd as they seem to correspond to

+47dBm in the case of "myHouse",this is more than your Wireless should be Transmitting.When you look at the graphical display what does the vertical axis show as signal level? Mine is normally around -50dBm. For my network(edited):- # $Creator: Network Stumbler Version 0.4.0 # $Format: wi-scan summary with extensions #Time (GMT) [ SNR Sig Noise ] 17:54:36 (GMT) [ 55 104 49 ] Gives me a signal level of -45 dBm at this time.
Reply to
Bob II

Hi Bob

The graphical representation of the signal/noise is all over the place. The highest number is roughly +41dBm, immediately followed by a low number of usually -40dBm (but sometimes down to -100dBm every thirty seconds or so), then followed by a number that is on average -30dBm. It cycles through the high, low, medium number pattern.

This seems to be a more detailed representation of the WiFi card's indicator in the system tray which cycles through poor/fair/excellent quality links; and the card Utility screen which also cycles through none/poor/fair/excellent quality link and signal strength.

Reply to
Martin Lowe
8>>>

Were these readings taken using the Dell Laptop?If so try your HP machine and see if you get similar readings using Netstumbler.I have never seen readings as high as +40dBm and unless you live next to a high power transmitter I would suspect a problem with your wireless card in the Dell, is it built in? Can you put it in the HP,disable the built in wireless, and repeat the test?

Bob

Reply to
Bob II

These readings were from the Dell.

On the HP (with its built-in WiFi) I get dBm readings ranging from -70dBm to -35dBm, with the occasional -100dBm reading every thirty seconds or so.

I haven't attempted putting the Belkin card from the Dell into the HP because it does seem to be the signal broadcast that is the problem. If I look at the other two networks, their signal/noise chart looks "blocky" because their signals maintain a relatively constant dBm reading whereas the chart for my network on both laptops is more akin to looking at a comb that's never been cleaned.

I get the same reception difficulty with both laptops, so even though the readings from the Dell/Belkin combo are an oddity, the main problem remains and I'm at a loss as to what to do next.

Reply to
Martin Lowe

Since your neighbours readings are stable then either you have a problem with your wireless router or there is someone else on Ch6, Netstumbler will not find "non-broadcast" SSID's. Change your routers wireless Channel to Ch1 and try the test again.

Bob

Reply to
Bob II

It seems to have helped both laptops to differing levels - the HP with onboard WiFi more so than the Dell with the Belkin card, which only shows minimal improvement. The signal is still more "spikey" than "blocky" though.

Reply to
Martin Lowe
8>

I think you have a problem with the Dell/Belkin combo and should not use that to find your other problem. Does it make any difference if you disconnect your network drive from the Router? What signal levels do you get if you are in the same room as the router? Can you borrow another wireless router to place in the same location to see if there is any difference?

Bob

Reply to
Bob II

The network drive makes no difference. I don't have a wireless router to borrow; in any case, I was wondering about replacing it and going to 11g - perhaps this is a good incentive to move, assuming of course that I don't end up with the same problem.

Thanks for all your help.

Reply to
Martin Lowe

At least you have had a play with Netstumbler.You will now be able to survey your house for the best locations to set up and use your WLAN. Best of luck.

Bob

Reply to
Bob II

If you're to migrate, give some serious thought to products based on Airgo Gen3 MIMO technology (currently Netgear and Linksys), which have greatly improved range and speed as compared to standard 802.11g.

Reply to
John Navas

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