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EZNEC What elevation angles should I use?
When I setup an antenna in EZNEC, I want to see the azimuth but the
program asks for an elevation angle. WHat angle should I use? I have been randomly using 5 or 10 deg. Thanks -- 73 for now Buck N4PGW |
Buck wrote: When I setup an antenna in EZNEC, I want to see the azimuth but the program asks for an elevation angle. WHat angle should I use? I have been randomly using 5 or 10 deg. Thanks -- 73 for now Buck N4PGW Hi Buck, Antennas have a 3-dimensional pattern. When you only want to see the Azimuth, you are looking at a 2D pattern, with a fixed elevation angle. The Azimuth plot must have an elevation angle to have meaning. The elevation angle you use depends on a number of factors. For instance, if you want to work dx, or want to hit a distant repeater, you want the most gain at low elevation angles. You want the Azimuth pattern to show the most gain at low elevation angles. I think 5-10 degrees qualifies as low angles. EZNEC shows on the elevation plot the angle where the gain is maximum. It also has a 3D plot that really gives a good indication of where you are squirting the most signal. Gary N4AST |
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Buck wrote:
. . . Thank you Gary, I have been looking at it a bit. I decided the best way to get an accurate reading for the highest gain is to look at the elevation and then set the azimuth elevation to the TOA. But what you're probably really interested in is the gain in the angle you'll be using for communication. Who cares what the maximum gain of the antenna is if that gain only occurs in directions (azimuth or elevation) you're not using for communication? First, decide what elevation angles will be used for communication. One way to find that is by using a propagation program like W6ELProp (which is free). Look at the gain at those angles with EZNEC. The elevation angle at which the gain is maximum is of very little practical use -- EZNEC reports it only because a lot of people wanted it (for reasons which remain mysterious to me). Roy Lewallen, W7EL |
On Wed, 15 Jun 2005 16:27:55 -0400, Buck wrote:
When I setup an antenna in EZNEC, I want to see the azimuth but the program asks for an elevation angle. WHat angle should I use? I have been randomly using 5 or 10 deg. Depends. If you want to see the whole picture, use a 3D plot. You should know that you can grab this with the mouse and change the angle of view. By turning on the "Highlights" you can get any cut you want on the pattern. Experiment. For a feature rich (and free) alternative that will give you these plots in living color see: http://www.si-list.org/swindex2.html#4nec2_ That said, and not taking anything away from Arie's masterful work, I recommend that you stick with EZNEC until you are more skilled at modeling. |
On Wed, 15 Jun 2005 16:19:58 -0700, Roy Lewallen
wrote: Tsk tsk. EZNEC reports it only because a lot of people wanted it (for reasons which remain mysterious to me). Don't you know that the customer is always right? [grin] |
The elevation
angle at which the gain is maximum is of very little practical use -- EZNEC reports it only because a lot of people wanted it (for reasons which remain mysterious to me). Roy Lewallen, W7EL =========================== Roy, good to see, at last, you've got rid of this popular misconception. ---- Reg. |
Wouldn't this 'gain' be useful in figuring out just where you could dump
your maximum signal somewhere in the world? It might not be where you want, but at least you might have an idea of where you would stick a loud signal using max gain at some elevation angle? Or is this a totally useless idea? I don't pretend to know what I'm talking about here, but it seems logical that by using this type of data it would help you figure out where you were going to put in a stronger signal. Shields up! Jer "Reg Edwards" wrote in message ... The elevation angle at which the gain is maximum is of very little practical use -- EZNEC reports it only because a lot of people wanted it (for reasons which remain mysterious to me). Roy Lewallen, W7EL =========================== Roy, good to see, at last, you've got rid of this popular misconception. ---- Reg. |
On Thu, 16 Jun 2005 14:44:15 GMT, "Jer"
wrote: Wouldn't this 'gain' be useful in figuring out just where you could dump your maximum signal somewhere in the world? It might not be where you want, but at least you might have an idea of where you would stick a loud signal using max gain at some elevation angle? Or is this a totally useless idea? I don't pretend to know what I'm talking about here, but it seems logical that by using this type of data it would help you figure out where you were going to put in a stronger signal. Shields up! Jer From the remarks I see on this forum and others, there appears to be a number of people who only consider how an antenna works for DX. There are many of us who don't just chase DX. I hunt counties and need antennas that will cover much smaller skip than someone trying to operate with russia from here. On late night nets, I need signals that drown out the 40 meter sw stations and so I can hear my regional QSOs. Other times, I would love to be able to pick out that rare DX in the midst of a pileup of multi-kw amps and beams that have more acreage than the average home. If someone needs 10-20 deg TOA for a signal, then they need to know how to maximize their antenna for that angle, that is true. I want to know the characteristics of the antennas to know how they will work for various purposes. No shield needed:) -- 73 for now Buck N4PGW |
I'm another Ham that could care less about DX! I just want to use the
proper frequency depending on the time of day/night to communicate with some friends located around the west coast. Very few DX stations will hold a rag chew, just slam bam, thank you mam, i.e. 599 OM !... ugh.. At any rate, if I knew more about my antennas characteristics I might could figure out the band/end location where it would be loudest at any given time. Is this all wet, and TOA wouldn't help in that at all? Jer "Buck" wrote in message ... On Thu, 16 Jun 2005 14:44:15 GMT, "Jer" wrote: Wouldn't this 'gain' be useful in figuring out just where you could dump your maximum signal somewhere in the world? It might not be where you want, but at least you might have an idea of where you would stick a loud signal using max gain at some elevation angle? Or is this a totally useless idea? I don't pretend to know what I'm talking about here, but it seems logical that by using this type of data it would help you figure out where you were going to put in a stronger signal. Shields up! Jer From the remarks I see on this forum and others, there appears to be a number of people who only consider how an antenna works for DX. There are many of us who don't just chase DX. I hunt counties and need antennas that will cover much smaller skip than someone trying to operate with russia from here. On late night nets, I need signals that drown out the 40 meter sw stations and so I can hear my regional QSOs. Other times, I would love to be able to pick out that rare DX in the midst of a pileup of multi-kw amps and beams that have more acreage than the average home. If someone needs 10-20 deg TOA for a signal, then they need to know how to maximize their antenna for that angle, that is true. I want to know the characteristics of the antennas to know how they will work for various purposes. No shield needed:) -- 73 for now Buck N4PGW |
On Thu, 16 Jun 2005 16:56:41 GMT, "Jer"
wrote: At any rate, if I knew more about my antennas characteristics I might could figure out the band/end location where it would be loudest at any given time. Is this all wet, and TOA wouldn't help in that at all? The TOA will help in any QSO. A low TOA will tend to open you up to DX QRM such as on 40 meters, but an NVIS with near vertical TOA will manage more regional communications than DX. You might not even be bothered by the 500kw SW station in Germany. Of course, the station you talk to will also have to deal with that station. Knowing the TOA is as beneficial as knowing where the nuls are on your beam. -- 73 for now Buck N4PGW |
Jer wrote:
Wouldn't this 'gain' be useful in figuring out just where you could dump your maximum signal somewhere in the world? It might not be where you want, but at least you might have an idea of where you would stick a loud signal using max gain at some elevation angle? Or is this a totally useless idea? I don't pretend to know what I'm talking about here, but it seems logical that by using this type of data it would help you figure out where you were going to put in a stronger signal. Shields up! No, I don't think it's a useless idea, just one that hadn't occurred to me. It will indeed tell you where your signal will be strong, assuming that propagation is supported in that azimuth direction and at that elevation angle. Roy Lewallen, W7EL |
Jer wrote:
I'm another Ham that could care less about DX! I just want to use the proper frequency depending on the time of day/night to communicate with some friends located around the west coast. Very few DX stations will hold a rag chew, just slam bam, thank you mam, i.e. 599 OM !... ugh.. At any rate, if I knew more about my antennas characteristics I might could figure out the band/end location where it would be loudest at any given time. Is this all wet, and TOA wouldn't help in that at all? The TOA isn't the way to get that information. What you need to do is, first, find out what elevation angle will be used for communication on each band at the time(s) of day of interest. Again, something like W6ELProp is good for doing that. Second, since you're interested in having the strongest signal, look at the signal strength reported by W6ELProp or other propagation program at each of those times. Next, use EZNEC to look at the gain of your antenna at the elevation angles you found with the propagation program. Finally, add the antenna gain to the signal strength reported by the propagation program at each band and time. The largest number will give you the best signal. This of course comes with the caution that propagation prediction is generally much less accurate than antenna pattern calculation, so there can be a lot of variability in the accuracy of the results. I think that if you go through this exercise a few times, you won't find much correlation between your results and the TOA. Roy Lewallen, W7EL |
Buck wrote:
The TOA will help in any QSO. A low TOA will tend to open you up to DX QRM such as on 40 meters, but an NVIS with near vertical TOA will manage more regional communications than DX. You might not even be bothered by the 500kw SW station in Germany. Of course, the station you talk to will also have to deal with that station. Knowing the TOA is as beneficial as knowing where the nuls are on your beam. That's a good and perfectly valid point. Knowing the TOA would be useful in determining what range of distances you're most likely to encounter QRM from. Roy Lewallen, W7EL |
Roy Lewallen wrote: The elevation angle at which the gain is maximum is of very little practical use -- EZNEC reports it only because a lot of people wanted it (for reasons which remain mysterious to me). Maybe the guys out at Goldstone can explain it. :-) ac6xg |
On Thu, 16 Jun 2005 10:41:19 -0700, Roy Lewallen
wrote: Buck wrote: The TOA will help in any QSO. A low TOA will tend to open you up to DX QRM such as on 40 meters, but an NVIS with near vertical TOA will manage more regional communications than DX. You might not even be bothered by the 500kw SW station in Germany. Of course, the station you talk to will also have to deal with that station. Knowing the TOA is as beneficial as knowing where the nuls are on your beam. That's a good and perfectly valid point. Knowing the TOA would be useful in determining what range of distances you're most likely to encounter QRM from. Roy Lewallen, W7EL Or what antenna to choose to avoid it. -- 73 for now Buck N4PGW |
On Thu, 16 Jun 2005 10:38:18 -0700, Roy Lewallen
wrote: Jer wrote: I think that if you go through this exercise a few times, you won't find much correlation between your results and the TOA. Roy Lewallen, W7EL Of course, he could just check to see which antenna hears the station the best with the least QRM. From what I understand, the TOA of a DX station changes over time. It may come in at a low angle and then rise a bit or visa versa. Or it may never get high enough for a particular antenna -- 73 for now Buck N4PGW |
Buck wrote:
When I setup an antenna in EZNEC, I want to see the azimuth but the program asks for an elevation angle. WHat angle should I use? I have been randomly using 5 or 10 deg. An example of an approach to antenna design that starts with identification of the paths to be optimised is at http://www.vk1od.net/7MDipole/7MDipole.htm . In this case, I was interested in local contacts and over 50% of Australia's population was located in just four cities at distances up to 1000Km. The propagation paths to those locations was modeled to provide the geometry for assessment of antennas in EzNEC. BTW, 5 to 10 degrees elevation is probably below most propagation paths for DX, let alone local contacts. Lowest angle doesn't necessarily translate to optimal for distant stations (it depends on the propagation mechanism at the time), and the most desirable DX might not be at the greatest distance. Best performance at low angles might assure maximum pickup of local noise sources, and in my case QRM because I am not at all interested in DX. Owen |
Owen wrote:
BTW, 5 to 10 degrees elevation is probably below most propagation paths for DX, let alone local contacts. Lowest angle doesn't necessarily translate to optimal for distant stations (it depends on the propagation mechanism at the time), and the most desirable DX might not be at the greatest distance. Best performance at low angles might assure maximum pickup of local noise sources, and in my case QRM because I am not at all interested in DX. Recent editions of the ARRL Antenna Book cover this topic very thoroughly. They note that arrival angles from a given location vary with time of day, time of year, time in the sunspot cycle, whether the ionosphere is stable or disturbed, and so on... Then they produce statistics for major paths (eg "G-VK"), averaged over all these factors. OK, so these figues are "only computed"... but they are computed using VOACAP (the Voice of America's propagation program that has has years of development and a lot of verification) so this is the best information we're ever likely to get. The big lesson is that there is ALWAYS A SPREAD OF POSSIBLE ANGLES. As Owen says, 5-10deg is not always the most likely angle. It all depends on how many F2/F1/E hops will fit into the required path length. That means the arrival angles tend to jump, especially as the band is coming on or going out. (However, it turns out that a substantial fraction of signals on the G-VK path come in at angles of only a degree or two. These paths are workable, of course, but the antennas at both ends will usually have very little gain unless the land slopes down to lower the reflection angle.) Hams became fixated on "5 to 10 degrees" a very long time ago, and we still tend to wave this figure around like some kind of flash-card. Professionals have moved on to a much better understanding of the range of possible angles that they need, and this is now starting to filter into ham radio too. If anyone is interested in this subject and hasn't read a recent edition of the ARRL Antenna Book, it's time for an update. -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
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