On Tuesday the 14th a few of our net members participated in the County frequency coordination test. The goal was to see if the amateur, FRS and GMRS frequencies selected by each group of communicators in the valley would overlap enough to result in communications disruptions.
We started on the primary net frequencies at 6:00 p.m. with a roll call check-in. From the EOC radio, I did not notice any interference on the amateur frequencies we have been using for our monthly radio nets. When all who could participate were checked in, we moved to the FRS/GMRS frequencies I had requested through the coordination process - channels 6, 10 and 12.
In an emergency, when the goal is to make contact with each household in the ward to determine status of persons and property damage, realizing we are limited in the number of amateur licensed operators, the help of persons using FRS and GMRS radios may increase the speed of gathering that information. This is why we have requested frequencies in these bands, to allow for use of low power FRS radios among the wards, who will then report their findings to the Stake via amateur radio frequencies - if normal modes of communication are not possible.
As background, In the FRS/GMRS band plan, channels 1 - 7 have a maximum output power of 2 watts on a FRS radio and 5 watts on a GMRS radio; channels 8 - 14 are limited to 0.5 watts transmit power regardless of the radio type used. Follow this link to view the current frequency chart for FRS and GMRS.
Additionally, there are repeater channels authorized for GMRS licensees, with transmit power of up to 50 watts. Locally there are 7 GMRS repeaters available for use in an emergency. Those repeaters will be shared by all of the groups who use GMRS in their emergency communications plan, making them very busy.
While most emergency communications groups in the area will use amateur radio frequencies when normal modes of communication fail, many of these groups have also requested frequencies in the FRS and GMRS band. With only 14 non-repeater frequencies available in these bands, avoiding overlap was impossible, but hopefully the distances between users would minimize the interference.
From our participation in the exercise Tuesday, we learned that the 3 frequencies chosen in the FRS and GMRS band had significant interference. I expected this on channel 6 which has a 5 watt limit for GMRS users on that channel, but I was surprised by the interference on channels 10 and 12. This was largely due to operators transmitting way outside the power limit of 0.5 watts.
If this were duplicated during an actual emergency, there would be too much interference to use these frequencies without applying tone squelch, however, tone squelch in an emergency is not recommended. While tone squelch can filter out unwanted interference, it will also prevent you from hearing anyone who is not using the exact same tone code, and in an emergency, you need to hear all potential rescuers or fellow survivors.
I am hopeful there will be constructive discussion regarding transmit power on FRS and GMRS frequencies during the next frequency coordination meeting in November. If necessary I will look into changing the FRS and GMRS frequencies that would be used in our communities by users with FRS radios or GMRS licenses.