Q: Airport Extreme wifi throughput issues

Airport is on channel 6, and I have another linksys used to extend the range on Channel 1 (which gets all of 3Mbs). No other wifi is visible on iStumbler.

Since 802.11n AirPort base stations can basically only extend other Apple base stations, are you saying that you are using a Linksys device to extend your AirPort Extreme? Is so, are you sure that it is actually extending it?

Or are you saying that you have the Linksys device connected by Ethernet to the Extreme and have both of them configured for a roaming network? If that's the case, then both routers should be broadcasting a Wi-Fi network on the same radio channel.

Then the Linksys is NOT extending the Extreme. I still need to understand if you have this Linksys connected to the Extreme by Ethernet? If it's not, then it is just broadcasting a second Wi-Fi network and not connected to any network at all.

Ok, thanks for clarifying that for me. Unless you have a specific need to have the Linksys broadcast a different Wi-Fi network, I would strongly suggest that you consider reconfiguring both for a roaming network. I provided you with a link earlier.

If this is not something you want to do, then I would suggest that you temporarily power-down the Linksys so that the AirPort is the only Wi-Fi network and take the data rate measurements again to see if there is any improvements.

Ok going back to the A1143 Extreme. This 1st generation model uses either the 2.4 GHz or 5 GHz radio for Wi-Fi, but not both simultaneously. It also has Fast Ethernet (100 Mbps) Ethernet ports, not Gigabit.

With the Linksys powered-down, I would expect that you should get potential Wi-Fi link rates up to 130 Mbps on the 2.4 GHz band between the Extreme and the MBP. Actual throughput would be about half this ... which is significantly more than you are getting now if you are measuring 500 Kbps - 3 Mbps.

Since you are using iStumbler what are the values for Signal (dBm) & Noise (dBm) when using iStumbler's Inspector feature? You will find this feature on iStumbler menu bar at Edit > Inspector. They should show up as negative values, not percentages.

Also please provide the values from the OS X AirPort icon when holding down the option key before selecting the icon. I am specifically interested in: PHY MODE, Channel, RSSI, Transmit Rate, & MCX Index values.

... and what is the model number of your Linksys device?

In the same room as the router, signal is anywhere from -23 to -39dBm, noise -81 to -92 dBM

That would give you a Signal-to-Noise Ratio range between 42 & 69 dB, which is an excellent score.

SNR (db) = Signal (dBm) - Noise (dBm)

-39 -(-81) = 42 & -23 -(-92) = 69

This would at least tell me that the signal quality in the same room is excellent, which it should be.

PHY Mode: 802.11n

Channel 6 (2.4GHz)

Your MBP is connected to the Extreme's 2.4 GHz Wi-Fi network on channel 6 in the 802.11n radio mode.

RSSI: -40

RSSI is the Received Signal Strength Indication. It is measured in arbitrary units. For Apple routers, the more negative the value the better the received signal. A RSSI value of -40 is good, but not great.

Transmit Rate: 117

MCS Index 14

The Transmit Rate is within the standard with a MCS Index value equal to 14. This value indicates that the Wi-Fi network established between the AirPort Extreme and the MBP is using two spatial streams. However, both this Extreme model and your MBP are both capable of connecting with three streams. (MCS values between 16 & 23)

Not sure why your MBP cannot establish a better connection with the Extreme, especially if they are in the same room ... and since the SNR values are so high.