User Manual
INSTRUCTIONS FOR USING THE RSSI TOOL
*RSSI Tool only available in DuraFon 1X and PRO handsets and DuraWalkies (v1.5 or v2) (ser#114000001 or
higher).
Base version is not important. To check firmware, press menu, star, star, pound (base number for 1x is “10” and “00” for
PRO), press 1 for SW VER.
1. “RSSI” stands for receive signal strength indicator. Usually for a phone (DuraFon as well) this is in the form of
several bars. The problem is this is simply not adequate for performing a real site survey. Industry standard for
measuring signals are in negative dBm. You do not need an admin handset for this test. All handsets can do this.
2. Base to handset link testing:
a. Press menu, star, pound, pound, star. Then press “1” for “BER”. Next choose the appropriate base (1x is
default ID10, PRO is base default 00, and 01-07 if you have additional base units). While in BER mode
press the “star” button. It will change the screen to –dBm and frequency deviation.
3. Handset to handset link testing: Why? Because 2-way intercom and broadcast operation normally (unless you
have a PRO repeater base) do not use the base station. This means range testing for these modes needs to be done
separately (not necessary if these modes of operation are not used).
a. First note which handset ID you have. Now press Menu, star, pound, pound, star, then press “2” for “HS
BER”. Then while the handset displays “HS BER READY”, grab another handset and 2-way call it. It will
automatically answer. Now press the star key to enter RSSI mode. Both handsets will see RSSI readings.
Frequency Deviation:
Deviation should not exceed 2000Hz at less than 25ft. from the base antenna. If it is more, there may be a hardware problem.
RSSI and –dBm:
The highest reading is around -47dBm even though the signal might actually be stronger because it only reads so high. It is
typical to maintain a signal of -55dBm or better for about the first 100 feet from the base station antenna.
The weakest signal that can be received is -110dBm. If you go beyond this, you will lose the link between the handset and
base. Note this is not the signal you want to set as your minimum signal for coverage! If you do lose the link between
handset and base, exit the menu, and enter back in it again.
It is typical to require 20 to 30dB of margin to maintain a reliable link and to compensate for varying conditions. This means
the signal should be -80dBm or better (better meaning less negative). A -65dBm signal is stronger than a -80dBm signal
because it is less negative. If you have any trouble with this, see the Wiki link below on “dBm”. To save time, note areas
where signal is -80dBm or worse only.
Signal >-80dBm = no dropped calls, no noticeable degradation in voice quality.
Signal -81dBm to -90dBm = low risk of dropped calls but a slight reduction in voice quality.
Signal -91dBm to -100dBm = real risk of random dropped calls and noticeable voice quality reduction.
Signal <-101dBm = terrible voice quality and dropped calls.
Signal <-110dBm = no link at all.
This assumes little to no interference in the 902-928MHz band. If you have severe interference, you will see poor performance even though RSSI is
strong. It is the signal to noise radio (margin) that matters. If you think there is a possibility of interference, you may want to purchase a 900MHz USB
spectrum analyzer to find the source. A product such as the MetaGeek Wi-Spy 900X is a relatively low cost option.
TESTING WITH SHORT VERSUS LONG HANDSET ANTENNA:
Do your testing with the antenna that will be actually used. There is a 2dB difference between the long and short antenna but
a 5 to 8dB difference when in actual use. This is because the long antenna extends beyond the person’s head so signal
attenuation is not as bad (you are testing while having the phone in front of you vs. next to your ear that is real world use).
Do not have any other handsets or bases in use during site survey testing.
If changes are made such as moving a base station antenna, do them one at a time and redo the entire site survey over again.
Do not do multiple changes at the same time as this will not allow you to know which of changes helped (or made worse).
Good sources for additional learning: http://en.wikipedia.org/wiki/DBm http://en.wikipedia.org/wiki/Rssi
http://en.wikipedia.org/wiki/Wireless_site_survey http://www.wireless-nets.com/resources/tutorials/conduct_wireless_site_survey.html
Revised 3.7.2014 Daniel Koczwara