Skip to content

Signal strength

It looks like Apple has stimulated some renewed interest in signal reports. Their latest cell phone has an antenna that is placed to keep the brain cancer folks happy but it can be easily hampered depending upon how you hold the phone. One problem Apple has was the phone signal strength indicators. Most cell phones use a 5 bar weak to strong signal indicator. This is like the Ham’s S meter. They can be deceptive.

cnet FAQ: What does the 5-bar signal strength icon really mean? has a good rundown on the issue.

With old time radios, signal strength was based on what the radio could pull out of the background noise. These days, a common power level to get a readable signal may be -100 dBm which is about a tenth of a trillionth of a watt (1e-13). A billions of a watt, -60 dBm, would usually be considered an excellent signal. By IARU standards a radio S-9 (very good signal) is equivalent to a power of -73 dBm for frequencies below 30 MHz. Each S unit is 6 decibels

My cable modem is reporting -12 dBmV down and 54 dBmV up. To convert volts to watts, you need to use the 75 ohm impedance of the cable. See From dB to S-point : Learn to play with power units (ON4SKY) for more on calculating signal strength in various units.

Post a Comment

You must be logged in to post a comment.