Several years ago I learned that a lot of frequency changes in the federal VHF 162-174 band were going to take place due to direction contained in the 2005 (or thereabouts) National Telecommunications and Information Redbook, which is the manual of regulations covering federal government use of radio frequencies. The 2005 edition made huge changes in federal frequency use and was issued at the time narrowbanding became mandatory for federal agencies, some 8 years prior to the requirement that state and local agencies had to do so also.
The direction included changes in how frequencies are used in the 162-174 MHz and 406-420 MHz bands. In each band three ranges of frequencies were prescribed. One for repeater output or downlink frequency use, one for simplex use and one for repeater input or uplink frequencies. In the UHF band the lower frequencies are allocated for repeater output/downlink use, the middle frequencies for simplex use and the upper frequencies for repeater input/uplink use. The allocation required that the separation between the output/input frequencies be exactly 9 MHz. The reverse is the case in of VHF. The upper frequencies are allocated for repeater output/downlink uses and the lower for repeater input/uplink uses.
A split between the two is not specified as VHF has been in use longer (mid to late 1950's) resulting in a more disorganized and disjointed situation for existing frequency assignments. Most frequency assignments were not made based on a specified split that applied to the entire band, so an effort to establish one is not possible, unless a difficult and highly disruptive frequency coordination and reassignment effort is made. A further complication exists as some 25 kHz spaced frequency assignments had been made based on 12.5 kHz spacing. For example 166.4875 was assigned to the BLM in California in the 1980's, which is halfway between 166.4750 and 166.5000 and appears to be a narrowband frequency, however specifications allowed a signal up to 25 kHz wide at the time.
Up to now, most of the effort to bring radio systems into compliance with the Redbook direction has been directed to the UHF band. Narrowbanding required new equipment and systems were built to comply with the new allocation. Most hobbyists who listen to federal VHF systems did not notice the changes because such systems often use UHF for linking only.
Now federal agencies are beginning the process of complying with the NTIA direction by making sure that simplex, input and output frequency use falls in the proper ranges. I thought the process would have been as easy as exchanging inputs for outputs, etc., however one or both of the existing frequencies would often fall into the simplex only range, thus requiring new assignments. Sometimes using a frequency for the output of a repeater brought up interference issues with other agencies. The result is something that may appear to be rather random and without logic, but this is not the case.
During my hospitalization (5 weeks) a relatively new source of mine shared sent me a document that shows the frequency changes the Forest Service in California (USFS Region 5 or Pacific Southwest Region) is going to make between 2015-2017. Some changes were made just after the Labor Day holiday this year and others are scheduled for 2017. I've revised the California National Forests wiki page channel plans to show all the changes shown in the document. Upcoming changes are shown in a separate table apart from the existing system table. Most of the changes will occur in 2016, either in the spring or fall. As the changes occur and people confirm they have been made, I will revise the original tables to reflect them.
Unfortunately, these changes are coinciding with the installation of a new, far more secure server that NIFC has set up for all radio system information. Old web addresses that have provided us with updates in the last few years will no longer yield any information. This makes our hobby that much tougher. For a retiree like myself, who wants to keep some connection to my former profession, career and agency; being able to listen to natural resource and fire agency radio traffic is important. It is becoming increasingly difficult for retirees to maintain this connection.
I have some access to information for federal agencies in California, but none for the rest of the country. Keeping the database accurate and current for all the other states is going to be very difficult.
OPTIONAL INFORMATION
It has taken me several hours to write this post. Pain, pain medication and being confined to bed most of the time has taken its toll on my cognitive functioning. The accident, one minor and two major surgeries, 5 weeks in a hospital located 180 miles from home, the severe nature of the lower back pain (I had a compression fracture in one vertebra) and the hard work of physical therapy have been rough. I face many months of hard physical therapy in the recovery process and expect that it's going to be an equal amount of time for my brain to recover. Please accept my apologies for my less than clear writing and for not answering PM's during this time. My intellect, just like my mobility, is going to be limited in the coming months.
The direction included changes in how frequencies are used in the 162-174 MHz and 406-420 MHz bands. In each band three ranges of frequencies were prescribed. One for repeater output or downlink frequency use, one for simplex use and one for repeater input or uplink frequencies. In the UHF band the lower frequencies are allocated for repeater output/downlink use, the middle frequencies for simplex use and the upper frequencies for repeater input/uplink use. The allocation required that the separation between the output/input frequencies be exactly 9 MHz. The reverse is the case in of VHF. The upper frequencies are allocated for repeater output/downlink uses and the lower for repeater input/uplink uses.
A split between the two is not specified as VHF has been in use longer (mid to late 1950's) resulting in a more disorganized and disjointed situation for existing frequency assignments. Most frequency assignments were not made based on a specified split that applied to the entire band, so an effort to establish one is not possible, unless a difficult and highly disruptive frequency coordination and reassignment effort is made. A further complication exists as some 25 kHz spaced frequency assignments had been made based on 12.5 kHz spacing. For example 166.4875 was assigned to the BLM in California in the 1980's, which is halfway between 166.4750 and 166.5000 and appears to be a narrowband frequency, however specifications allowed a signal up to 25 kHz wide at the time.
Up to now, most of the effort to bring radio systems into compliance with the Redbook direction has been directed to the UHF band. Narrowbanding required new equipment and systems were built to comply with the new allocation. Most hobbyists who listen to federal VHF systems did not notice the changes because such systems often use UHF for linking only.
Now federal agencies are beginning the process of complying with the NTIA direction by making sure that simplex, input and output frequency use falls in the proper ranges. I thought the process would have been as easy as exchanging inputs for outputs, etc., however one or both of the existing frequencies would often fall into the simplex only range, thus requiring new assignments. Sometimes using a frequency for the output of a repeater brought up interference issues with other agencies. The result is something that may appear to be rather random and without logic, but this is not the case.
During my hospitalization (5 weeks) a relatively new source of mine shared sent me a document that shows the frequency changes the Forest Service in California (USFS Region 5 or Pacific Southwest Region) is going to make between 2015-2017. Some changes were made just after the Labor Day holiday this year and others are scheduled for 2017. I've revised the California National Forests wiki page channel plans to show all the changes shown in the document. Upcoming changes are shown in a separate table apart from the existing system table. Most of the changes will occur in 2016, either in the spring or fall. As the changes occur and people confirm they have been made, I will revise the original tables to reflect them.
Unfortunately, these changes are coinciding with the installation of a new, far more secure server that NIFC has set up for all radio system information. Old web addresses that have provided us with updates in the last few years will no longer yield any information. This makes our hobby that much tougher. For a retiree like myself, who wants to keep some connection to my former profession, career and agency; being able to listen to natural resource and fire agency radio traffic is important. It is becoming increasingly difficult for retirees to maintain this connection.
I have some access to information for federal agencies in California, but none for the rest of the country. Keeping the database accurate and current for all the other states is going to be very difficult.
OPTIONAL INFORMATION
It has taken me several hours to write this post. Pain, pain medication and being confined to bed most of the time has taken its toll on my cognitive functioning. The accident, one minor and two major surgeries, 5 weeks in a hospital located 180 miles from home, the severe nature of the lower back pain (I had a compression fracture in one vertebra) and the hard work of physical therapy have been rough. I face many months of hard physical therapy in the recovery process and expect that it's going to be an equal amount of time for my brain to recover. Please accept my apologies for my less than clear writing and for not answering PM's during this time. My intellect, just like my mobility, is going to be limited in the coming months.
