CAl Fire Air Ops "South Ops"
- Thread starter SCPD
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They are on the state microwave backbone.
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.
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.
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Polarization Nation
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.
-Mike
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.
-Mike
Wow
Exsmoky,
I have to commend you on your bank of knowledge, it is truly remarkable. I live in Atascadero, Ca just south of Paso Robles, in San Luis Obispo County. An I would love it if you could Advise me of what frequencies i should try. Please PM me or email me at email .conner .here@gmail.com (with out the spaces of course) if you are ever in the area, I would love to meet you and rack your brain.
Thanks
Conner
Exsmoky,
I have to commend you on your bank of knowledge, it is truly remarkable. I live in Atascadero, Ca just south of Paso Robles, in San Luis Obispo County. An I would love it if you could Advise me of what frequencies i should try. Please PM me or email me at email .conner .here@gmail.com (with out the spaces of course) if you are ever in the area, I would love to meet you and rack your brain.
Thanks
Conner
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?
If so I have mixed the two polarizations for quite some time. It makes sense that the horizontal polarization results in a narrower signal, in terms of azimuth, than that of a vertically polarized signal, that can be received over a wider azimuth.
Thanks for pointing this out to me. Doing so caused me to look up a lot of discussions on this topic and I am now corrected.
Antenna Polarization
Exsmokey,
Well...based on what you just wrote I am now getting confused;-()! Ok, the way I was taught and the way I have continued to read it in texts subsequently, is that antenna "polarization" is based on the electrical half of the electromagnetic wave. The magnetic half is always 90 degrees out of phase with the electric half. So, a "straight up and down" or vertically polarized signal would have the electric portion oscillating "vertically" relative to the earth's surface; this would be mechanically analogous to you jumping up and down in one place. The magnetic portion would be perpendicular to the electric portion so it would oscillate "from side to side". To be most effective, the antenna for a vertically polarized signal should be (ideally) "straight up and down". Normal car whip antennas, "rubber duckies" (held correctly, i.e. vertically), vertically polarized beams (the driving and radiating elements all would be perpendicular to the base of the antenna/earth's surface - you jumping up and down again), etc. all would be examples of vertically (ideally) polarized antennas.
Horizontally polarized antennas would have the radiating elements arranged parallel with the earth's surface - you moving from side to side. This is relatively easy for fixed base station beam antennas to be engineered for and mechanically manipulated but not so easy for mobile use. By tipping your handheld on its side you can get a relatively bidirectional horizontally polarized "antenna system" for a typical portable with an unmodified standard portable whip or rubber ducky antenna. Aside from the obvious relative mechanical difficulties involved in directly implementing them in a mobile scenario, the other problems with horizontally polarized antennas are that it takes more thought and engineering to create an omni-directional horizontally polarized antenna. It can be done and certainly is but the usual designs do tend to look a bit odd to the uninitiated. Square loops and, I think, egg beater-type, antennas (not sure about the latter) are examples of this. Another typical cheap fixed example is the crossed half-wave folded dipole antenna frequently used, at least in the past, for omni-directional reception of broadcast FM signals. And another, even cheaper, and, I would think, less effective example is the "S" folded dipole antenna (looks like an "S" when viewed from above).
For most common antenna types, you can tell what the polarization is simply by seeing whether the elements are straight up and down (vertically polarized) or arranged sideways (horizontally polarized). However, some antennas do not follow this rule (at least not obviously). Notably, the quad beam directional antenna and the common discone (TRUE discone, with no vertical whip add-ons). The quad has elements that are either both vertical and horizontally arranged or the same but tipped 45 degrees (I am getting into my ignorance zone here (on quads) so I suspect more quad antenna-savy folks may check me - be warned). As I understand it, for quads, it depends on how the antenna is fed - how the feedline is connected to the antenna. I think it depends on whether the feed is connected to the vertical element or to the horizontal element; there may be other methods, I am not sure. In any case, just by looking at a quad beam from a distance it may not be obvious what polarization it is set for. I think some designs actually used a switching system to allow the user to switch polarization remotely from the operating position (I seem to remember a series of cubical quad antennas designed for CB use and later for 10 meter amateur use way back in the heyday of the CB craze that did this - I think the brand was "Avanti" or some such).
The true discone is, by nature, an omni-directional vertically polarized antenna. But if you look at it it seems to have no vertically radiating elements. It gets its vertical polarization from (crudely put here for simplicity) roughly the interplay between the top disc portion and the conical bottom portion according to a mathematical formula. That also dictates the ratio of disc-to-cone size which (again oversimplified here) ultimately dictates the lowest effective frequency for the discone (which, ideally with perfect parts and construction in a free space vacuum would have nearly infinite upper frequency limit hence the discone's notable broad banded reputation). Anyway, again, if you don't know anything about discones then just by looking at them you might not see an obvious vertically polarized antenna - but they are.
In any case, the reasons to choose vertical vs. horizontal polarization (and BTW, you CAN choose any polarization not just vertical or horizontal - those are just the two most common choices; an example is circular polarization with a further choice of right handed or left handed circular polarization - this is commonly used for space-earth communication often using helical antennas) are varied and usually based on practicality vs. need. One reason to "go horizontal" is to gain some atmospheric and man-made noise rejection which has a lot of its energy close to the vertical plane relative to the earth surface at the receiving station. Another reason is that it is claimed that in the HF portion of the spectrum wherein common long distance communication is obtained by reflecting signals from the earth's ionosphere it is more effective to use horizontal polarization versus vertical polarization - as I recall, I have read of some debate among experts here so that is why I wrote "claimed" above. Mechanically, it seems a tad easier to mount and rotate beams in the lower HF spectrum horizontally then to do so vertically; this, together with the simple fact that it is just a standard for HF long distance use, is why you so often see those large HF Yagi beam antennas with their horizontally arranged elements atop houses with lucky amateur radio operators that have no antenna restrictions ;-)!
On VHF and above, I am not sure whether the noise problem is a major deciding factor as both atmospheric and man-made noise tends to go down relative to the HF spectrum (though you might disagree when in close proximity with modern computer hardware!). Also, since so much of the VHF and above spectrum is used for local land-mobile (containing many car and handheld users) communication it is just easier to make everything primarily vertically polarized - makes it cheap and easy to use standard whips on cars and handhelds plus they are, ideally, relatively omni-directional which is most practical for a mobile environment. Now, if all you want is to communicate fixed point-to-point as in a base station to base station setup or a linked repeater setup you could go either way no problem as you aren't concerned with communication with mobiles or handhelds. So, you might go with horizontal polarization simply to reduce interference from co-channel and in-band vertically polarized signals from other users. At the higher VHF and UHF frequencies it's pretty easy to set a typical Yagi beam as a horizontally polarized antenna for fixed station to fixed station use - standard beam just mount it physically such that the elements are parallel with the earth's surface relative to the base of the station's antenna mount. I think this is why many link stations use horizontal polarization - to reduce interference from in-band and co-channel undesired vertically polarized signals. I actually am ignorant of the directionality characteristics of vertically polarized beams versus horizontally polarized beams (with otherwise identical designs); off the top of my unfortunately insufficient head I can't see why, in an ideal sense with all other factors being equal and neglecting terrain topology and atmospherics, there should be a difference but, again, I'm just stupid on this point and someone with better knowledge than I will likely correct me here.
Also, it should be noted that, as signals get bounced around and reflected, their polarization can vary from the initiating desired "perfect" vertical or horizontal ideal. So, at a distance, the destination station may get something considerably off from the original polarization which will cause extra loss - just par for the course in the real world. This is especially true as you get to shorter and shorter wavelengths - one reason that cross polarized and circularly polarized antennas are sometimes used to reduce such effects. Obviously, fixed-to-fixed usage experiences this less than would fixed-to-mobile or mobile-to-mobile usage.
In your case - maybe they do use vertical polarization for linked repeaters?!? I couldn't say one way or the other. I suspect it's up to the techs on a situational basis. If they want to reduce interference from other users in-band that are primarily vertically polarized then they might go horizontal but if they don't need to do this then they might not. Again, there may be a directional characteristic to this also I just don't know.
If they do use vertical polarization for fixed linked repeater usage then the only loss a non-system listener with a typical handheld, mobile, or base scanner antenna would experience aside from standard path loss due to terrain topology, atmospherics, and distance would be from being outside the directional beam's ideal signal path and not to opposite polarization loss (again, neglecting the nearly unavoidable changes in polarization that the signal may experience on its journey to the receiver).
So, I think, based on the first part of your last post your initial understanding was correct. With the exception of some, most antennas will polarize their transmitted signals depending on the orientation of the radiating elements (relative to the electric portion of the electromagnetic wave). Horizontal elements means horizontal polarization (parallel to the surface relative to the antenna base) and vertical elements means vertical polarization (perpendicular to the surface relative to the antenna base).
My confusion, then, comes from your earlier post wherein you seem to imply that the link antennas have a special characteristic with regard to their polarization relative to a typical scanner listener that they need to take into consideration and, possibly, compensate for if possible - if they are truly vertically polarized, as you say, then there is no such consideration necessary since most scanner users will have vertically polarized antennas. Relative location outside the system's directional beams' intended path obviously WILL have an impact on said listener, of course, but not polarization (ideally).
So, as far as I can tell, don't change your understanding of polarization - you have, or had, it right as (for most antenna designs) element orientation directly, and NOT inversely, relates to polarization of the electric portion of the electromagnetic wave. But, as far as I know, this is totally independent of directionality characteristics all other factors being equal and neglecting effects from terrain topology, etc.
Sorry I got so long winded, or rather worded - I actually had more but it wouldn't let me post as I was over the limit so I had to shorten it! And hope I didn't confuse you more!
-Mike
Exsmokey,
Well...based on what you just wrote I am now getting confused;-()! Ok, the way I was taught and the way I have continued to read it in texts subsequently, is that antenna "polarization" is based on the electrical half of the electromagnetic wave. The magnetic half is always 90 degrees out of phase with the electric half. So, a "straight up and down" or vertically polarized signal would have the electric portion oscillating "vertically" relative to the earth's surface; this would be mechanically analogous to you jumping up and down in one place. The magnetic portion would be perpendicular to the electric portion so it would oscillate "from side to side". To be most effective, the antenna for a vertically polarized signal should be (ideally) "straight up and down". Normal car whip antennas, "rubber duckies" (held correctly, i.e. vertically), vertically polarized beams (the driving and radiating elements all would be perpendicular to the base of the antenna/earth's surface - you jumping up and down again), etc. all would be examples of vertically (ideally) polarized antennas.
Horizontally polarized antennas would have the radiating elements arranged parallel with the earth's surface - you moving from side to side. This is relatively easy for fixed base station beam antennas to be engineered for and mechanically manipulated but not so easy for mobile use. By tipping your handheld on its side you can get a relatively bidirectional horizontally polarized "antenna system" for a typical portable with an unmodified standard portable whip or rubber ducky antenna. Aside from the obvious relative mechanical difficulties involved in directly implementing them in a mobile scenario, the other problems with horizontally polarized antennas are that it takes more thought and engineering to create an omni-directional horizontally polarized antenna. It can be done and certainly is but the usual designs do tend to look a bit odd to the uninitiated. Square loops and, I think, egg beater-type, antennas (not sure about the latter) are examples of this. Another typical cheap fixed example is the crossed half-wave folded dipole antenna frequently used, at least in the past, for omni-directional reception of broadcast FM signals. And another, even cheaper, and, I would think, less effective example is the "S" folded dipole antenna (looks like an "S" when viewed from above).
For most common antenna types, you can tell what the polarization is simply by seeing whether the elements are straight up and down (vertically polarized) or arranged sideways (horizontally polarized). However, some antennas do not follow this rule (at least not obviously). Notably, the quad beam directional antenna and the common discone (TRUE discone, with no vertical whip add-ons). The quad has elements that are either both vertical and horizontally arranged or the same but tipped 45 degrees (I am getting into my ignorance zone here (on quads) so I suspect more quad antenna-savy folks may check me - be warned). As I understand it, for quads, it depends on how the antenna is fed - how the feedline is connected to the antenna. I think it depends on whether the feed is connected to the vertical element or to the horizontal element; there may be other methods, I am not sure. In any case, just by looking at a quad beam from a distance it may not be obvious what polarization it is set for. I think some designs actually used a switching system to allow the user to switch polarization remotely from the operating position (I seem to remember a series of cubical quad antennas designed for CB use and later for 10 meter amateur use way back in the heyday of the CB craze that did this - I think the brand was "Avanti" or some such).
The true discone is, by nature, an omni-directional vertically polarized antenna. But if you look at it it seems to have no vertically radiating elements. It gets its vertical polarization from (crudely put here for simplicity) roughly the interplay between the top disc portion and the conical bottom portion according to a mathematical formula. That also dictates the ratio of disc-to-cone size which (again oversimplified here) ultimately dictates the lowest effective frequency for the discone (which, ideally with perfect parts and construction in a free space vacuum would have nearly infinite upper frequency limit hence the discone's notable broad banded reputation). Anyway, again, if you don't know anything about discones then just by looking at them you might not see an obvious vertically polarized antenna - but they are.
In any case, the reasons to choose vertical vs. horizontal polarization (and BTW, you CAN choose any polarization not just vertical or horizontal - those are just the two most common choices; an example is circular polarization with a further choice of right handed or left handed circular polarization - this is commonly used for space-earth communication often using helical antennas) are varied and usually based on practicality vs. need. One reason to "go horizontal" is to gain some atmospheric and man-made noise rejection which has a lot of its energy close to the vertical plane relative to the earth surface at the receiving station. Another reason is that it is claimed that in the HF portion of the spectrum wherein common long distance communication is obtained by reflecting signals from the earth's ionosphere it is more effective to use horizontal polarization versus vertical polarization - as I recall, I have read of some debate among experts here so that is why I wrote "claimed" above. Mechanically, it seems a tad easier to mount and rotate beams in the lower HF spectrum horizontally then to do so vertically; this, together with the simple fact that it is just a standard for HF long distance use, is why you so often see those large HF Yagi beam antennas with their horizontally arranged elements atop houses with lucky amateur radio operators that have no antenna restrictions ;-)!
On VHF and above, I am not sure whether the noise problem is a major deciding factor as both atmospheric and man-made noise tends to go down relative to the HF spectrum (though you might disagree when in close proximity with modern computer hardware!). Also, since so much of the VHF and above spectrum is used for local land-mobile (containing many car and handheld users) communication it is just easier to make everything primarily vertically polarized - makes it cheap and easy to use standard whips on cars and handhelds plus they are, ideally, relatively omni-directional which is most practical for a mobile environment. Now, if all you want is to communicate fixed point-to-point as in a base station to base station setup or a linked repeater setup you could go either way no problem as you aren't concerned with communication with mobiles or handhelds. So, you might go with horizontal polarization simply to reduce interference from co-channel and in-band vertically polarized signals from other users. At the higher VHF and UHF frequencies it's pretty easy to set a typical Yagi beam as a horizontally polarized antenna for fixed station to fixed station use - standard beam just mount it physically such that the elements are parallel with the earth's surface relative to the base of the station's antenna mount. I think this is why many link stations use horizontal polarization - to reduce interference from in-band and co-channel undesired vertically polarized signals. I actually am ignorant of the directionality characteristics of vertically polarized beams versus horizontally polarized beams (with otherwise identical designs); off the top of my unfortunately insufficient head I can't see why, in an ideal sense with all other factors being equal and neglecting terrain topology and atmospherics, there should be a difference but, again, I'm just stupid on this point and someone with better knowledge than I will likely correct me here.
Also, it should be noted that, as signals get bounced around and reflected, their polarization can vary from the initiating desired "perfect" vertical or horizontal ideal. So, at a distance, the destination station may get something considerably off from the original polarization which will cause extra loss - just par for the course in the real world. This is especially true as you get to shorter and shorter wavelengths - one reason that cross polarized and circularly polarized antennas are sometimes used to reduce such effects. Obviously, fixed-to-fixed usage experiences this less than would fixed-to-mobile or mobile-to-mobile usage.
In your case - maybe they do use vertical polarization for linked repeaters?!? I couldn't say one way or the other. I suspect it's up to the techs on a situational basis. If they want to reduce interference from other users in-band that are primarily vertically polarized then they might go horizontal but if they don't need to do this then they might not. Again, there may be a directional characteristic to this also I just don't know.
If they do use vertical polarization for fixed linked repeater usage then the only loss a non-system listener with a typical handheld, mobile, or base scanner antenna would experience aside from standard path loss due to terrain topology, atmospherics, and distance would be from being outside the directional beam's ideal signal path and not to opposite polarization loss (again, neglecting the nearly unavoidable changes in polarization that the signal may experience on its journey to the receiver).
So, I think, based on the first part of your last post your initial understanding was correct. With the exception of some, most antennas will polarize their transmitted signals depending on the orientation of the radiating elements (relative to the electric portion of the electromagnetic wave). Horizontal elements means horizontal polarization (parallel to the surface relative to the antenna base) and vertical elements means vertical polarization (perpendicular to the surface relative to the antenna base).
My confusion, then, comes from your earlier post wherein you seem to imply that the link antennas have a special characteristic with regard to their polarization relative to a typical scanner listener that they need to take into consideration and, possibly, compensate for if possible - if they are truly vertically polarized, as you say, then there is no such consideration necessary since most scanner users will have vertically polarized antennas. Relative location outside the system's directional beams' intended path obviously WILL have an impact on said listener, of course, but not polarization (ideally).
So, as far as I can tell, don't change your understanding of polarization - you have, or had, it right as (for most antenna designs) element orientation directly, and NOT inversely, relates to polarization of the electric portion of the electromagnetic wave. But, as far as I know, this is totally independent of directionality characteristics all other factors being equal and neglecting effects from terrain topology, etc.
Sorry I got so long winded, or rather worded - I actually had more but it wouldn't let me post as I was over the limit so I had to shorten it! And hope I didn't confuse you more!
-Mike
Antenna Polarization Part 2
Exsmokey,
Sorry, I'm a detail freak and couldn't resist posting what I had to leave out in my last post (I think you're like-minded in that sense, no?!). So here is, for lack of a better title, Part II:
TV station signals, BTW, are traditionally horizontally polarized, as, I think, you initially understood. This is because, when initially setup they probably wanted to both reduce broadband noise and reduce interference from LMR users plus, since it was all fixed station receiving points (back in the day before portable and mobile TV receivers became as common as they are now) you didn't have to worry about mobile horizontally polarized antenna use. Also, I recall reading (or hearing - not sure which now) that broadcast FM stations often used something like a 45 degree polarization so that it was a compromise between horizontally polarized fixed antennas and common vertically polarized "car radio" whips. I really don't know if that was true and, if so, if they even still do this. Just some odd thingy I recall.
Another thing to keep in mind is that the further the signal from a directional antenna travels the wider the beam width becomes - it spreads out from the source. Regardless of the polarization and regardless of the beam antenna's designed beam width as the signal travels further and further from the source it will continue to spread out. The tighter the designed beamwidth of the transmitting antenna the tighter the initial beam will be, of course, but it will still spread out as distance increases. So, an outside listener can be more off center from the intended path if they are further from the source so long as they are not at an extreme angle relative to the source (neglecting reflections, multipath, etc.). Of course that doesn't necessarily mean that further away is better since standard path loss still applies so if your close to the source you may be fine since no beam is 100% perfect and what you lose in being outside the initial tight beam signal path you gain in relative signal strength from off center radiation.
And you can get lucky from reflections from mountains, etc.
Again, really enjoy your postings! Hope this didn't put you to sleep!
-Mike
Exsmokey,
Sorry, I'm a detail freak and couldn't resist posting what I had to leave out in my last post (I think you're like-minded in that sense, no?!). So here is, for lack of a better title, Part II:
TV station signals, BTW, are traditionally horizontally polarized, as, I think, you initially understood. This is because, when initially setup they probably wanted to both reduce broadband noise and reduce interference from LMR users plus, since it was all fixed station receiving points (back in the day before portable and mobile TV receivers became as common as they are now) you didn't have to worry about mobile horizontally polarized antenna use. Also, I recall reading (or hearing - not sure which now) that broadcast FM stations often used something like a 45 degree polarization so that it was a compromise between horizontally polarized fixed antennas and common vertically polarized "car radio" whips. I really don't know if that was true and, if so, if they even still do this. Just some odd thingy I recall.
Another thing to keep in mind is that the further the signal from a directional antenna travels the wider the beam width becomes - it spreads out from the source. Regardless of the polarization and regardless of the beam antenna's designed beam width as the signal travels further and further from the source it will continue to spread out. The tighter the designed beamwidth of the transmitting antenna the tighter the initial beam will be, of course, but it will still spread out as distance increases. So, an outside listener can be more off center from the intended path if they are further from the source so long as they are not at an extreme angle relative to the source (neglecting reflections, multipath, etc.). Of course that doesn't necessarily mean that further away is better since standard path loss still applies so if your close to the source you may be fine since no beam is 100% perfect and what you lose in being outside the initial tight beam signal path you gain in relative signal strength from off center radiation.
And you can get lucky from reflections from mountains, etc.
Again, really enjoy your postings! Hope this didn't put you to sleep!
-Mike
Uplink
Member
Exsmokey, You rock!, Excellent and informative, you are what Radioreference is all about. Great Post! Thanks
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And just to confuse things further, and add another layer of complexity, because of the high RF environments at altitude, more back-haul links that are not microwave are moving to circular polarized antennas, similar to satellite uplinks.
So you have circular right and circular left polarization.
Technology marches on.
So you have circular right and circular left polarization.
Technology marches on.
Circular logic...er, polarization
Yeah, that's been around awhile at least for space-earth communications as I mentioned but I didn't know about them being used in terrestrial links though I am not surprised for the reason you mentioned.
Anyway, I feel like I inadvertently hijacked this thread for which I profusely and wholeheartedly apologize to Exsmkey, the Admin's, and all interested others. I get way too carried away on technical issues.
I really am interested in the original topic (South Ops, etc.) and am sorry to all that I brought it so off topic!
50 lashes about the head and shoulders with a stiff rubber ducky for me I'm afraid!
-Mike
Yeah, that's been around awhile at least for space-earth communications as I mentioned but I didn't know about them being used in terrestrial links though I am not surprised for the reason you mentioned.
Anyway, I feel like I inadvertently hijacked this thread for which I profusely and wholeheartedly apologize to Exsmkey, the Admin's, and all interested others. I get way too carried away on technical issues.
I really am interested in the original topic (South Ops, etc.) and am sorry to all that I brought it so off topic!
50 lashes about the head and shoulders with a stiff rubber ducky for me I'm afraid!
-Mike
Finally heard SouthOps in Carlsbad!
Back on topic...
I finally heard "SouthOps" on the 166.5625 (Santiago) just yesterday, 8/25/2008. It was weak but readable with my handheld. Heard both sides on 166.5625. Tried listening on 415.525 but nothing though that's likely me as I have heard that frequency active here before but very weak. I'm in the Lake Calaveras area of Carlsbad.
-Mike
Back on topic...
I finally heard "SouthOps" on the 166.5625 (Santiago) just yesterday, 8/25/2008. It was weak but readable with my handheld. Heard both sides on 166.5625. Tried listening on 415.525 but nothing though that's likely me as I have heard that frequency active here before but very weak. I'm in the Lake Calaveras area of Carlsbad.
-Mike
What type of scanner and antenna were you using? The 166.5625 is interesting as it it being aimed north from Santiago toward Frazier.
The weakness in audio is probably due to narrow banding. The new GRE scanners have an audio boost feature that allows narrow banded channels to be boosted up to almost equal the audio output of the wider band channels. Starting in 2013 there will be very few wide band frequencies left.
I haven't had time to look through the discussion of the polarization yet. It is my understanding that the vertically aligned elements on a Yagi indicate horizontal polarization. If this is not correct I will find out when I read the appropriate posts above.
The weakness in audio is probably due to narrow banding. The new GRE scanners have an audio boost feature that allows narrow banded channels to be boosted up to almost equal the audio output of the wider band channels. Starting in 2013 there will be very few wide band frequencies left.
I haven't had time to look through the discussion of the polarization yet. It is my understanding that the vertically aligned elements on a Yagi indicate horizontal polarization. If this is not correct I will find out when I read the appropriate posts above.
DPD1
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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.
But yes, the polarization matches the orientation of the elements. Vert = Vert. For instance the typical TV ant. is horizontal.
Dave
www.DPDProductions.com
Antennas & Accessories for the RF Professional & Radio Hobbyist
But yes, the polarization matches the orientation of the elements. Vert = Vert. For instance the typical TV ant. is horizontal.
Dave
www.DPDProductions.com
Antennas & Accessories for the RF Professional & Radio Hobbyist
SouthOps
Exsmokey,
I am using a PSR500; already have the audio boost on plus the NFM IF filter (I've determined through experimentation that the GRE's NFM mode engages a narrower IF filter but, as far as I can determine, that's all it does, hence necessitating the use of the audio boost as you say). Anyway, I meant weak in signal not audio deviation. I cannot mount an outside antenna (at least not overtly) and am presently only using a rubber ducky on the unit. Actually, it's the RS 800MHz duck so it's very inefficient on 166MHz! I used my hand to couple myself to the antenna roughly inductively to bring the inherent capacitive reactance of the antenna (due to being electrically so short at 166MHz) down a tad and thereby improve the signal strength (just what I had available at the time - my body!).
Anyway, I was just interested that I could pick it up at all! I tried listening on the 164MHz frequency but no joy on that one. I have been getting alot of tropo ducting on the 800MHz frequencies lately due to the weather so that may be affecting the VHF stuff a bit also. I am within site of many eastern mountains and can receive many eastern sourced signals. I receive Riverside County and San Bernardino County (parts, anyway) rather well - better at most times than even Orange County which is just north of me. I am also fairly certain that I get a myriad of reflections from the mountains so I could just be lucky in getting either a tropo or geological "pipe" between me and the Santiago link; again, it is weak and I'm not yet sure how reliable, I'll have to monitor more extensively with a better antenna.
I have received the 415.525MHz link in the past but that is very iffy. According to your posts it should link down to the Monte Vista command center south of me but, if so, I must not be in the link path, at least not in a very good spot within it. On this occasion, I did not receive anything on the 415.525MHz link (I did lower the squelch all the way, BTW). All the more interesting that I got the 166.5625MHz signal at all!
And yes, thanks Dave, that's what I was trying to explain earlier - antenna polarization is directly related to the antenna elements for standard yagi's and whips unless you are talking about the magnetic portion of the wave but, by convention, we use the electric portion when speaking of polarization.
Really don't want to hijack this thread and get all off topic though! I think I did that enough already! We can PM each other about antenna polarization if you want.
-Mike
Exsmokey,
I am using a PSR500; already have the audio boost on plus the NFM IF filter (I've determined through experimentation that the GRE's NFM mode engages a narrower IF filter but, as far as I can determine, that's all it does, hence necessitating the use of the audio boost as you say). Anyway, I meant weak in signal not audio deviation. I cannot mount an outside antenna (at least not overtly) and am presently only using a rubber ducky on the unit. Actually, it's the RS 800MHz duck so it's very inefficient on 166MHz! I used my hand to couple myself to the antenna roughly inductively to bring the inherent capacitive reactance of the antenna (due to being electrically so short at 166MHz) down a tad and thereby improve the signal strength (just what I had available at the time - my body!).
Anyway, I was just interested that I could pick it up at all! I tried listening on the 164MHz frequency but no joy on that one. I have been getting alot of tropo ducting on the 800MHz frequencies lately due to the weather so that may be affecting the VHF stuff a bit also. I am within site of many eastern mountains and can receive many eastern sourced signals. I receive Riverside County and San Bernardino County (parts, anyway) rather well - better at most times than even Orange County which is just north of me. I am also fairly certain that I get a myriad of reflections from the mountains so I could just be lucky in getting either a tropo or geological "pipe" between me and the Santiago link; again, it is weak and I'm not yet sure how reliable, I'll have to monitor more extensively with a better antenna.
I have received the 415.525MHz link in the past but that is very iffy. According to your posts it should link down to the Monte Vista command center south of me but, if so, I must not be in the link path, at least not in a very good spot within it. On this occasion, I did not receive anything on the 415.525MHz link (I did lower the squelch all the way, BTW). All the more interesting that I got the 166.5625MHz signal at all!
And yes, thanks Dave, that's what I was trying to explain earlier - antenna polarization is directly related to the antenna elements for standard yagi's and whips unless you are talking about the magnetic portion of the wave but, by convention, we use the electric portion when speaking of polarization.
Really don't want to hijack this thread and get all off topic though! I think I did that enough already! We can PM each other about antenna polarization if you want.
-Mike
DPD1
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Spoke too soon... Just heard somebody on the .9125. I guess they just don't talk a lot.
Dave
www.DPDProductions.com
Antennas & Accessories for the RF Professional & Radio Hobbyist
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