Like every other website on the planet, SmallNetBuilder uses cookies. Our cookies track login status, but we only allow admins to log in anyway, so those don't apply to you. Any other cookies you pick up during your visit come from advertisers, which we don't control.
If you continue to use the site, you agree to tolerate our use of cookies. Thank you!

Router Charts

Click for Router Charts

Router Ranker

Click for Router Ranker

NAS Charts

Click for NAS Charts

NAS Ranker

Click for NAS Ranker

More Tools

Click for More Tools

Wireless How To

Measuring Signal Strength

I considered a number of tools for measuring signal strength before settling on NetStumbler. NetStumbler provides a nice signal strength vs. time plot that can easily be stopped when moving between locations. It also has pretty good WLAN chipset / card support, including the two cards that I wanted to use: the D-Link WNA-2330 (Atheros based) and Linksys WPC54G (Broadcom based).

WLAN cards aren't the most accurate signal meters around. But they are good enough for what we're trying to do because we need only relative signal strength. I started by using the D-Link WNA-2330 card associated with a Linksys WRT54G wireless router. I didn't run any traffic—these measurements were made using the WRT54G's beacons only.

Figure 3 shows signal strength vs. location for my five test locations, plus a few others that are described in the figure callouts.

Signal Strength vs. Location - D-Link WNA-2330 card
Click to enlarge image

Figure 3: Signal Strength vs. Location - D-Link WNA-2330 card

Note that the largest signal drop occurs between the first two measurement points—"Antennas touching" and Location 1 (about 3 ft. away). Since RF power follows the inverse-square law, you can see that we're dealing with very low levels of energy pretty quickly as we move away from the access point.

Table 2 takes the Signal Level readings from Figure 3 and relates them to an equivalent path loss, which is then overlaid on a downlink throughput vs. path loss plot for the card in Figure 4.

Test Location Signal Level (dBm) Delta Equiv.
Path Loss
Location 1 -45 46 60
Location 2 -62 29 77
Location 3 -66 25 81
Location 4 -85 6 100
Location 5 -91 - 106
Table 2: D-Link WNA-2330 Signal Levels

This is simply done by taking Location 5 as a reference and assigning it to the last plotted point. The last point is used as the reference instead of Location 1 because it's easy to tell when you lose signal. The values in the Delta column in Table 2 are then subtracted from the Path Loss value of the last plotted point to get the path loss values for the other Locations.

Signal Strength vs. Location - D-Link WNA-2330 card

Figure 4: Path Loss vs. Location - D-Link WNA-2330 card

Figure 4 shows the results, with the locations overlaid on a downlink throughput vs. path loss plot.

More Wireless

Wi-Fi System Tools
Check out our Wi-Fi System Charts, Ranker and Finder!

Support Us!

If you like what we do and want to thank us, just buy something on Amazon. We'll get a small commission on anything you buy. Thanks!

Over In The Forums

I have been having a problem with wireless home automation devices staying on the network as described here:
This is FlexQoS, a fork of the original, groundbreaking FreshJR_QOS script written by @FreshJR.FlexQoS provides a fully customizable Adaptive QoS expe...
Asuswrt-Merlin 384.19 beta is now available (except for the RT-AX56U which won't be available for this release, due to outdated GPL code).The main cha...
I have 384.18 currently but this was on the last build as well. My system log shows these entries multiple times and several times a day:"dnsmasq[437]...
Is there a way to block all DNS on port 53 except for a specified device? I looked at SkyNET and the Asus WebUI and didn't see anything that really fi...

Don't Miss These

  • 1
  • 2
  • 3