YagiCAD Tips Tricks and Examples
1. In 6.x - Clicking on the "All dimensions shown in " label on the YagiCAD front page cycles through the available options from Metres, to Inches , to Wavelengths. The change will only effect the current session unless you happen to go into Tools/Options during that session.
2. In 5.x, and up, the maximise, resonate, etc. auto optimise functions work best and quickest if the changes required are small. Eg. If the element length is already close to the best value and just fine tuning is required. Sometimes if values are far enough away from the optimum point the optimize function can give-up/timeout. In these cases it is best to manually try and vary the values by macro amounts to get roughly right, and then use the auto optimise.
3. In 6.x, the effect described in Tip 2 can show up when dealing with the Quad and Folded Dipole types. In particular when wanting to go from a design with a normal dipole driven element to a folded one just changing the element type and then say auto resonating the driver starting from the same length can have problems. You can manually shorten (usually the case) the now folded element by some guess and try again as per tip 2. Another way of handling this is to (prior to changing the element type) use the Folded Dipole equivalent diameter in the tools menu to give you an equivalent diameter, then use this in the scale tool to scale the driven element to this new diameter. The element can then be changed back to the original diameter and type changed to folded and the length will be reasonably close to resonance etc. Certainly close enough for the Auto optimize functions to be used. An example of a Yagi where this was done can be seen here in BVO2_2wlFD.YC6
4. In 6.1.x the MultiElement can be used other than for a trigonal etc. reflector. For example a number of 2 element multi elements can be used together to form a corner reflector. See example 2mCornerReflector.YC6. This simple antenna has reasonable gain, excellent pattern, and very, very good bandwidth.
5. In 6.x Noel D'hont on5Ui gives us an example of a simple three element Quagi for 2Metres. 3 elm q yagi 144,30 new version.YC6 This can be scaled using the scaling tool to further up the 2M band or to other bands entirely.
6. In 5.x and up there are three options for boom correction factors G3SEK, NBS, and custom. The G3SEK is also known as the DL6WU and as used in YagiCAD is a correction factor for insulated through boom mounting, while the NBS one is intended for uninsulated through boom. The custom version is intended for use where some other method of calculating a boom correction factor is used such as experimental measurement. All are approximations only and this is why in 6.x and up the corrected lengths are shown in a separate column.
7. In 5.2 and up the key to getting genetic optimisation to work as you would want it is in setting appropriate values for the weights. The page here gives some ideas on how to do this and some other aspects of optimisation.
8. In 6.1 there is also a folded dipole element here is an example of an eight element yagi that uses the folded dipole as driver where the optimisation has been set for a wide band width but with a net 100 Ohm impedance. This antenna is useful in that if you are wanting to use a pair for circular polarization having an impedance of 100 ohms is convenient as the two 100s in parallel will give you 50 Ohms, and that 100 Ohm balanced transmission line is very easily made from two runs of 50 Ohm coax with the shields connected at each end and the two inners used as the 100 Ohm line.
9. In 6.x the model convergence test was included, apart from seeing if your model converges this can also be used to figure out how many segments you need to get the accuracy required. Typically you will note that the gain will converge with fewer segments than say input impedance. So if you are going to do some optimising and are only worried about gain then you can get away with fewer segments. Similarly the effects of single verses double precision can be see typically by single showing instabilities at higher numbers of segments.
10. In 6.x if you want to quickly change the number of segments for all elements of a Yagi design, just open the design, go into tools, options and change the number of default segments to the value you want on the Yagi. As well as changing the default this will also change all the values in the currently open Yagi. You can then save the Yagi, and if required return the number of default segments to its original value in the option menu.
11. In 5.x and up if you want to check out the YagiCAD results in another package then you can export the current Yagi in standard NEC2 card deck image by using the file, export menu.
12. In 5.x and up if you need to do some graphing of results, or data combining several models or conditions, each YagiCAD results window contains an export to comma separated value file menu option. These files are easily imported into packages such as MS excel or equivalent where they can be charted with considerably more flexibility than available in YagiCAD.
13. In 6.1.x when gain is displayed in dBi a value is shown in brackets after the gain which is the value for optimal gain for that boomlength Yagi, and is based on information from the ARRL Antenna handbook. This gives an indication/reference of how good the Yagi is. Note this optimal value is for Yagi's with simple dipole elements.
14. In 6.1.6 and up if you have different band endges to the default ones you just need to edit the banddata.txt file. In this file are pairs of frequencies a low end comma high end all in MHz. The order entered does not matter other than the first pair reading from the top that YagiCAD finds that contains the current Yagi frequency will be used as the band edges. So for example if you wanted to have a narrow band mode band as well as the whole band for 6m in Australia you could have on one line say 50, 52.5 and on the next 50, 54 in this case if the Yagi frequency is say 51MHz then the first found band edges will be 50 to 52.5, if however the Yagi frequency is 53 then the band edges will be 50 to 54 . Of course you can always override the chosen band edges in the program but if you have to do it each time it can be a nuisance, also of course if the Yagi frequency you have chosen is not between any listed bands then an arbitary +- 5% figure is used as the default.
15. In 6.x and up to complete changing a field you need to have left that field. eg if you want to change the main Yagi frequency on the main page you need to click or tab to the frequency field, edit the number to the new frequency, then click or tab off to some other field before the actual changed frequency will be registered. If say you edited the frequency then without moving to another field you say ran a basic calculation the original frequency value would be used not your changed one. This applies for pretty much all fields through out Yagicad.
16. In 6.1 and up when you select other than a plain dipole for the driven element all of the match options other than direct connection are disabled. YagiCad has two more or less mutually exclusive ways of dealing with a folded dipole feed. The original method that has been there since YagiCAD day one is to do all the method of moments (ie. nec2) modeling using dipole elements to calculate an input impedance and then use transmission line equivalent based mathematical models to calculate a match afterwards( ie. as per the ARRL antenna handbook etc.). This is the where the majority of the match types in the tools match menu come in. The other way, specifically for the case of the equal diameter folded dipole, that YagiCad has added in the last couple of releases, is to directly model the folded element in the same method of moments arrangement as the rest of the antenna. This later method is a more accurate method with a lot less approximations but is somewhat limited as NEC2 cannot handle close spaced unequal diameter elements/segments well. As a numerical example if say using all dipole elements the driven element input impedance came out of the NEC2 model as about 50 Ohms, then the folded dipole match type when applied in the tools section with say equal diam arms you would expect that it should roughly increase the input impedance by 4 to have it come out at about 200 Ohms. If however you were to call the driven element a folded type in the main screen then YagiCAD will add more segments to the NEC2 model to directly model the folded dipole and hopefully directly calculate the impedance of roughly 4 times the dipole equivalent and come out directly at the 200 ohms. Using the newer NEC2 approach does show much more clearly the effect of a folded dipole driver on the rest of the array, because it is there for all of the calculations not just applied afterwards. So anyway if the Tools/Match did let you add a folded dipole match to an already folded dipole element then you would get very strange results indeed. If you want to play with the ratio of elements diameters, or add series C etc. in a folded dipole driver then leave the driven element in the main screen marked as dipole (not folded dipole). If you want the most accurate model ( with only limited variables of folded dipole, basically just spacing) then mark it as a folded dipole in the main screen and the tools match section just lets you effectively say what transmission line impedance you will be using with a direct connection to the now folded element. A similar situation applies in the quad etc. element cases.
17. The NEC2 model that YagiCAD uses is not perfect, and there will be differences between the actual world and the idealized world modeled by YagiCAD. One of the more common non-ideal items is the effects of ground and nearby conducting objects. One of the special cases of this is the use of a conducting boom. My experience with YagiCAD is that given a non-conducting boom and several wavelengths separation from the ground the results from YagiCAD models are very close to actual results. If conductive booms are used the results will still be relatively correct and can be made closer to absolutly correct by appling a correction factor. The various boom correction factors used in YagiCAD are (like the tool matches) something applied after and over the top of the NEC2 model. The boom factors are (certainly in the YagiCAD case) experimentally determined correction factors worked out usually backwards ie. what number do I have to multiply the element length by so that the model results agree with actual measurements. The base correction factors in the YagiCAD case are ones that are commonly used in Ham work based on the experimental work of DL6WU (credited to G3SEK in YagiCAD because he did the work to turn the DL6WU data into a more computer friendly equation) and the American National Bureau of Standards but as even a quick glance will tell you these two factors come out with ( slightly) different results as both are effectively based on the actual specific element boom and mounting technique that they used for their antennas. A quick search on the web will find you many different correction factors used by individual people. At the end of the day though the best correction factor for you, especially if you have measured differences between actual and modeled for your antenna, may be a that number that makes those two results the same.
18. With respect to length of elements the length given in YagiCAD is the length of the radiating element, which even in the case of a split driven element, is equal to the distance between the two outer end points or the physical length if you will. This is because you have to feed that split with something. For example in a direct coax connection to the split you separate the braid from the centre of the coax to form a pair of pigtails which you then join, one to each side of the driven element, so even if the gap was say 100mm each pigtail would have to be about 50mm long so the total length of non-coax ( ie. including the pigtails which effectively bridge the gap) is still pretty much the distance between the ends of the element no matter what you do. Of course if you had a very big gap (or in the extreme case just used long coax pigtails for the element) then you are effectively varying the diameter of the element for the length of that gap and the YagiCAD /NEC2 calculations may be off a bit, but so long as you make the gap (and thus the pigtails) as short as possible its as close as you are going to get in practice. So there is no conversion formula needed for end physical length, if anything you need to do it the other way, ie. if you have a 10mm gap then the total length of say aluminum you need to make up that physical length with a 10mm gap is the length given by YagiCAD less 10mm, which will be made up by the coax pigtails. It is a different story for metal boom corrections but in that case YagiCAD gives you both the non-boom ideal length and an estimate of the physical length allowing for the boom correction selected.
19. in 6.* and up the initial splash screen that comes up when you start the program has a done button on it, this button is there because I reuse this form for the help about screen and you need to click it then to exit the help about. You do not need to click the done button when the program is initially starting up, it will automatically go away after a while. Clicking this button during the initial start up may cause some strange things to happen. Under the same heading as strange things happening, always try and exit YagiCAD in the normal manner in particular don't exit while the main window is minimised or hidden, if you do windows "being helpfull" will remember the windows state on exit and when it restarts subsequently start it minimised etc. This is true for most windows programs so if you are in the habbit of having lots of programs running at once with some of them minimised etc. don't just shutdown do a bit of a cleanup first. Of course it is not the end of the world if you don't but it can be a bit disconcerting if you think you have started a program and can't find it because it is minimised.
20. Late model Windows such as Vista and Windows 7 do not like users changing the contents of files in the Program Files directory. As YagiCAD stores its configuration etc. files in the same directory as the executables this causes a problem if you have installed YagiCAD in the pre 6.1.7 default location of Program Files. If you have windows Vista or 7 then everything will work much nicer if you install in the new default which is a directory under your user documents and settings. Alternately just changing it during the install to something like C:\Yagicad6 works well also. If you are installing over the top of an existing installation ie. doing an upgrade, the install program will detect this and start off with the current directory. If this is in Program files and you have been having problems with saving configuration or antenna description files then uninstall the old version of YagiCAD first before installing the new one in a non-Program Files directory. Don't forget to save a copy somewhere else of any antenna description files you have created / want to keep before uninstal, you can then be copy them to where-ever you install the new version.
21. If you want to design or analyse Yagis created with tapered elements then you can convert between uniform diameter elements and tapered ones via the manner indicated in the ARRL Antenna handbook. This method was described initially by Dr. David B. Leeson in his book Physical Design of Yagi Antennas. To add in this conversion you can use a spreadsheet produced by the ARRL to go with the Book. Alternatly if you just want the basic element calculations of equivalent diameters and lengths and don't need the mechanical strength ones as of version 6.1.7 YagiCAD has a simplified XLS speadsheet which is installed in the same directory as the main program. Instructions are on the sheet, basicaly type the taper schedule for one half of each element into the green cells and read off the equivalent length and diameter in the blue ones.If you want to go back the other way you can get close manually entering what is roughly correct then calculate the more exact equivalence using the error cells and the solver function in Excel to say vary the length of the last taper segment to minimise the error term.
If you have any tips, tricks or examples you want to share please mail them to me at my YagiCAD email address which can be derived by adding my call sign ie. VK3DIP, to the standard ending of the at symbol and YagiCAD.com.