I guess my understanding of the principle of polarization was based on the vertical vs. horizontal orientation of the antenna itself. Almost all links I have seen have beam antennas that have their elements arranged vertically or perpendicular with the earth's surface. I now understand that the actual polarization is 90 degrees different from the orientation of the antenna. Horizontally oriented signals would be carried on antennas that have their elements perpendicular to the earth's surface and vertically polarized signals, such as TV stations use, have beam antennas that are aligned parallel with the earth's surface. Is this correct?Exsmokey,
Excellent information - I always enjoy your very informative posts! However, just a minor niggle on my part with this post...did you actually mean that the link antennas are "horizontally" polarized rather than vertically as you said? Vertical polarization is standard and easy to implement in LMR mobile and portable equipment while horizontal polarization is often used to reduce atmospheric and artificial noise (mostly vertically polarized, sorta kinda) and for linked repeater setups such as those you are describing. If the repeaters you are describing actually use vertical polarization than the only loss a non-system listener, with a typically vertically polarized antenna as is commonly used with mobile and portable scanners, will experience, aside from normal path loss due to distance and the usual environmental factors, will be from being offset from the beam's focus rather than from any loss inherent in opposite polarization reception. Just wondering.
Ok, South Ops is not just a Cal Fire entity. The actual name is "Southern California Geographic Area Coordination Center." It is one of 11 such Geographic Area Coordination Centers (GACC) around the United States. These centers handle wildland fire activity for all agencies with wildland fire jurisdiction within their geographic area. As such they are an interagency or multiple agency organization. South Ops as it is commonly referred to, has employees from Cal Fire, the U.S. Forest Service, the Bureau of Land Management, the National Park Service, the U.S. Fish and Wildlife Service, and the Bureau of Indian Affairs. The National Weather Service is another agency that provides essential services to each of the 11 GACC's. Coordination between GACC's is provided by the grand daddy of all wildland fire dispatching and coordination and it is known as the National Interagency Fire Center or NIFC, and is located at the airport in Boise, Idaho. NIFC coordinates the movement of resources between GACC's and sets the priorities of so called "national resources" which consist of all aircraft, smokejumpers, and hotshot crews, as well as National Incident Management Teams.
As far as I know there is just one GACC with a radio network that connects all the wildland dispatch centers within the GACC and that is South Ops. It consists of three mountain top cross band repeaters. The hub site is Frazier Peak, located in the northeast portion of Ventura County. It provides coverage to all the San Joaquin Valley dispatch centers as well as a link to Santa Ynez Peak near Santa Barbara, that in turn links to the dispatch center for the Los Padres National Forest. The third site is located on Santiago Peak in southern Orange County, right on the Riverside County boundary. Santiago is linked to Frazier.
Now that you know where the sites are let me explain the frequencies that are used. First Frazier is linked to Santiago and transmits to it on 164.9125. Santiago transmits back to Frazier on 166.5625. Frazier is linked to Santa Ynez with the same two frequencies by transmitting to it on 164.9125 and Santa Ynez transmits back to Frazier on 166.5625. This completes how each of the 3 mountain top cross band repeaters is linked by VHF.
Each dispatch center is linked to one of the three mountain tops using UHF frequencies. The southern California dispatch centers and South Ops transmit to Santiago Peak on 411.525 and Santiago then transmits back to those same dispatch centers on the down link of 415.525. In the L.A. Basin, extending from Banning to the ocean and from Newhall to Temucula you should be able to hear the South Ops net on the down link frequency of 415.525. The last time I received this net I found that the down link of 415.525 was repeating the traffic from the up link of 411.525. This is important as you only had to listen to the down link to hear all of the traffic on the net. All of the dispatch centers north of the Grapevine link to Frazier using the same down link and up link frequencies. The Los Padres National Forest dispatch center uses these same frequencies to link with Santa Ynez Mtn.
It is important to note that each signal is vertically polarized, that is they use a beam antenna and it is pointed sideways so that the width of the signal is restricted somewhat to the path between it and the next mountain top or dispatch center. The exception is that a omni-directional antenna is probably used on Santiago as it receives the up link transmission from several locations in the L.A. Basin and at the Monte Vista dispatch center in Rancho San Bernardo where CDF and the Cleveland National Forest operate a joint dispatch center together. If you are in the greater L.A. Basin you should be able to receive the down link on 415.525 quite nicely. If you are in the San Fernando Valley you might not be able to receive UHF from Santiago but may have to try listening to the VHF link frequency of 166.5625 that Santiago transmits to Frazier. The disadvantage is that this signal is vertically polarized so you have to be close to the path from Santiago to Frazier to receive it. You will not be able to receive the 164.9125 transmission that Frazier uses to link to Santiago unless you are in the southern portion of the San Fernando Valley.
I think that only the UHF frequencies repeat the up link traffic on the down link. If you can't receive the UHF frequencies then you only get one side of the conversations in many cases. This can be a very confusing network to understand.
IF you are fortunate enough to be located where you can hear this UHF down link on 415.525, then you will not only hear dispatch centers in southern California, but will hear traffic between the dispatch centers in the San Joaquin Valley. You might hear the Sequoia National Forest dispatch center calling the CDF center in Visalia concerning a fire bordering CDFand the Sequoia National Forest. You may hear the Sierra National Forest advising Yosemite National Park of the resources it is sending to help them on a wildland fire in the Park.
This net was designed and constructed many years ago, well actually decades ago, when computers were not being used to link dispatch centers together as they are now linked. This has greatly reduced the voice traffic between dispatch centers and South Ops. Still, if you can manage to receive one of the frequencies above, you are going to get another source of information. It functions as a dispatchers intercom. Typical traffic consists of a dispatch center that has an air base telling South Ops and the receiving dispatch center of the ETA of an aircraft to a fire. You may hear something like "Angeles, Cleveland, Tanker 87 off the ground at 1417, ETA to your incident near Pyramid Lake is 1439." This would be for an air tanker stationed at Ramona. You might hear some traffic such as "San Bernardino, Angeles, Engines 38 and 39 responding to your incident near Cajon Pass, on-scene ETA 1655."
There is a computer program used to track resources and sometimes the off the ground and ETA times are just posted there and no voice traffic occurs. It is important to note that the aircraft and other fire resources such as engines and crews do not have access to this net. It is a net connecting many fixed base locations, those being the dispatch centers and South Ops. Fire resources call their local dispatch center with status and ETA's on the local net. The dispatch center then takes that information and advises South Ops and the receiving dispatch center with this information using the computer, the phone, or this South Ops net.
Now some changes in the way federal radio frequencies are used have been occurring this year. The up link and down links for repeaters on the UHF band used to have 4 MHz separation with the down link being the higher frequency of the two. Now they are supposed to have 9 MHz of separation with the down link being the lower of the two. At last report the frequencies I've given you were being received in late June and early July. I don't think the radio techs will make any changes until fire season quiets down some, but I can't say that for sure. If you don't hear anything on the frequencies I've given you then some frequency searches between 406 and 420 MHz will need to be done to locate the new frequencies.
I hope this explains the situation. It helps to know whether a fire is located on FRA, Federal Responsibility Area, SRA, State Responsibility Area, or LRA or Local Responsibility Area. Most large fires eventually involve all three when they are located in southern California and instead of having one incident commander has a Unified Command, with representatives of each agency sharing the incident command responsibility.
It is important to know the differences in jurisdiction as the agency with the most acreage eventually takes the lead. The lead agency dispatch center then becomes the ordering point for all responding resources. I've listened to recordings of fires that start in LRA in the city or county near the base of the San Bernardino Mountains, then move up slope onto SRA where Cal Fire or CDF takes the command, and eventually up onto the San Bernardino National Forest, and the lead agency status passes to them as the fire then involves more National Forest land and more focus than LRA or SRA. It is a good thing that all the initial attack personnel of each agency know the on the ground people in all the other agencies. This reduces the confusion of a fast moving fire that is working its way into several jurisdictions in a short period of time.
I hope this helps. You asked for a radio frequency and I added how that frequency is used as well. If you tell me your general location, I can probably give you some advice on which frequency to listen to.
Spoke too soon... Just heard somebody on the .9125. I guess they just don't talk a lot.I've had the 415.525, 166.5625 and 164.9125 on for a day and haven't heard anything from the SF valley. Guess I'm out of luck in this spot.