[TowerTalk] Yagi Optimizer file "Match" line
George Dubovsky
n4ua.va at gmail.com
Mon Sep 25 05:44:06 EDT 2017
Dan,
Here's the manual from 7.61. It looks like the first number in the line,
the "2", might be the type of match, and what follows are the particulars
for that match. I can't get YO to run on this Win10 machine or I'd check
that out.
73,
geo - n4ua
On Sun, Sep 24, 2017 at 11:52 AM, Stan Stockton <wa5rtg at gmail.com> wrote:
> Dan,
>
> I've got the manual somewhere on some computer. I'll look for it in the
> next day or two if you still need it.
>
> Stan, K5GO
>
> Sent from Stan's IPhone
>
>
>
> > On Sep 23, 2017, at 11:15 AM, Chuck Dietz <w5prchuck at gmail.com> wrote:
> >
> > There is a way to calculate the match parameters in YO. I don't use it.
> > That may be the output for that calculation. If you run that .YAG file in
> > YO, it should tell you.
> > There is no manual that I know of.
> >
> > Chuck W5PR
> >
> >> On Sat, Sep 23, 2017 at 10:48 AM, Chuck Dietz <w5prchuck at gmail.com>
> wrote:
> >>
> >> Where does this line appear? is it just above the element table? Is
> it a
> >> 6 meter yagi file?
> >> The line just above the element table is the diameter of the tubing for
> >> each element section. The table below lists the lengths
> >>
> >> 6 El 6M beam on 24' Boom
> >> Stacked 240.000
> >> 50.000 50.150 50.300 MHz
> >> 6 elements, inches
> >> 1.5000 0.8750 0.6250 0.4375
> >> 0.0000 3.5000 21.0000 23.5000 14.5340
> >> 36.6370 3.5000 21.0000 23.5000 10.0887
> >> 70.8626 3.5000 21.5000 23.5000 7.4651
> >> 145.4953 3.5000 21.5000 23.5000 6.0914
> >> 211.4772 3.5000 21.5000 23.5000 5.3854
> >> 288.0000 3.5000 21.5000 23.6027 0.0000
> >>
> >> Made from Hy-Gain 104CA
> >> Data for 2 beams stacked with 20' spacing. Gamma match
> >>
> >> The stuff below the table are the notes manually typed in.
> >> The low-center-high frequencies for optimization are listed just below
> the
> >> "240.000"
> >> maybe the file is scrambled.
> >>
> >> Chuck W5PR
> >>
> >> On Sat, Sep 23, 2017 at 12:58 AM, Dan Maguire via TowerTalk <
> >> towertalk at contesting.com> wrote:
> >>
> >>> I have a K6STI YO (.yag) file that has this line:
> >>>
> >>> Match: 2 0.3750 4.5000 54.0000 6.0000 0.0 50.0 0.0800
> >>>
> >>> Can anyone interpret those parameters for me? And a second question,
> >>> does anyone have any documentation for YO files that explains this
> line?
> >>> Perhaps the user manual for the most recent (?) version of YO?
> >>>
> >>> Dean Straw's "Yagi for Windows" manual does a good job of describing
> "YO
> >>> like" file formats but doesn't mention a "Match" line.
> >>>
> >>> Thanks.
> >>>
> >>> Dan, AC6LA
> >>> _______________________________________________
> >>>
> >>>
> >>>
> >>> _______________________________________________
> >>> TowerTalk mailing list
> >>> TowerTalk at contesting.com
> >>> http://lists.contesting.com/mailman/listinfo/towertalk
> >>>
> >>
> >>
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk at contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
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>
-------------- next part --------------
YO 7.5 YAGI OPTIMIZER
Copyright 2004 by Brian Beezley, K6STI
All Rights Reserved
YO 7.5 Yagi Optimizer..........................1
Using YO.......................................1
F/B and F/R....................................3
Frequency Menu.................................3
Height Menu....................................4
Elements Menu..................................4
Element Tapering...............................5
Mounting Brackets..............................6
Boom Correction................................7
Conductivity Loss..............................8
Performance Tradeoffs..........................9
Good-Enough Thresholds........................10
Local Optimizer...............................10
Global Optimizer..............................11
Undoing Changes...............................12
Matching Networks.............................13
Dual Driven Elements..........................16
Frequency Scaling.............................17
Output Files..................................18
Options Menu..................................19
Element-Current Profile.......................20
Frequency Graphs..............................20
Pattern Plots.................................20
Arrays of Yagis...............................22
Gain Figure-of-Merit..........................23
Modeling Limitations..........................23
Verifying Designs with NEC....................24
Notepad.......................................25
Screen........................................25
Mouse.........................................26
YO.SET........................................26
Index.........................................32
---- YO 7.5 YAGI OPTIMIZER -------------------------------------
YO analyzes and optimizes Yagi-Uda antenna designs on
your PC. It runs much faster than NEC- or MININEC-based
antenna-analysis programs. YO's mathematical model is more
complex than the W2PV Yagi model, simpler than MININEC, and more
accurate than either. YO models tapered elements, mounting
brackets, the boom, matching networks, dual driven elements, and
conductor loss. YO represents antennas in free space or over
ground. It can model two identical Yagis stacked in the H-plane
in free space. YO calculates mutual-impedance interactions for
all of these cases. It also can ignore Yagi-to-Yagi interaction
and model large rectangular arrays of Yagis.
YO includes an automatic optimizer that can maximize
forward gain and input resistance, and minimize backlobes,
sidelobes, and SWR. The optimizer iteratively adjusts element
lengths and spacings to optimize performance objectives you
specify using parameter tradeoffs you decide. It can perform
both local and global optimization.
YO is calibrated to NEC, the reference-accuracy
Numerical Electromagnetics Code from the Lawrence Livermore
National Laboratory. YO and NEC results normally differ by less
than 0.05 dB in forward gain, a dB or two in F/B, and a couple
ohms in input impedance. You can invoke NEC from within YO to
verify results.
YO's analysis and graphics engines use assembly language
with pipelined floating-point code optimized for Pentium
processors.
---- USING YO --------------------------------------------------
YO stores information for Yagi designs in individual
files. Yagi files contain antenna dimensions, analysis
frequencies, and other data. You provide the name of a Yagi
file when you start YO. After YO loads the file, you can
examine or modify the design. You can save the current design
in a file at any time. Yagi files use the extension .YAG.
If you know which Yagi file you want, provide the
filename on the command line, for example, YO HG204BA (no
extension needed). Otherwise, type YO, and the program will
list Yagi files in the current directory. To list Yagi files in
a different directory, provide the directory name on the command
line.
Select a file by moving the lightbar with the arrow
keys, PgUp, PgDn, Home, or End. Press Enter to select the
highlighted file. Or, you can select a filename by typing it.
As you type, the lightbar moves to the first filename that
matches the characters entered. Press Enter whenever the
desired file is highlighted. Finally, you can select a filename
by clicking on it with the mouse. Select "Other" to enter a
1
file or directory name not listed. If you enter a directory
name, YO will list its Yagi files. See the YO.SET section to
organize Yagi files into directories.
Press Esc to erase the Main menu. Press it again to
erase the tradeoffs triangle. Press Enter to restore the Main
menu.
Press Esc to return to the Main menu from another. You
also can return by pressing the command key a second time (first
keystroke only for Save and Notes). This quick-return feature
is handy when making a quick check.
Instead of pressing Enter after typing input, press Esc
to enter the data and exit the menu in one keystroke. Whenever
you return to the menu, the cursor will be positioned at the
item last entered. This makes it easy to change a value
repeatedly to experiment with its effect.
Press an arrow key after typing input to enter data and
move the cursor up, down, right, or left in one keystroke.
Press the spacebar to enter data without advancing to another
item. This feature is handy when experimenting with numerical
values.
Press any command key to exit a menu (except Save and
Notes). YO will execute the command, bypassing the Main menu.
This is a quick way to go from one menu to another. If you
press a command key during data entry, YO accepts the data and
performs the command.
When you enter data with more precision than that
displayed, YO accepts the data as entered. You can enter
fractional data; for example, type 1-15/32 instead of 1.46875.
Use the # key to enter wire gauge; for example, #12.
Press any nonfunctional key (F1, for example) to list
control keys not shown in the Main menu.
To reduce screen clutter, YO does not label the figures
displayed within the Yagi patterns. They are as follows:
Frequency
Forward Gain & Mismatch Loss
Front-to-Rear Ratio
Input Impedance
Standing-Wave Ratio
Elevation Angle or Gain FOM
Mismatch loss is displayed only when the option is
enabled. Elevation angle is displayed for Yagis over ground and
gain figure-of-merit for free-space, single-Yagi models. YO
defaults to a generalized definition of front-to-back ratio
described in the next section.
2
The notation 12.7-j15.4 means a resistance of 12.7 ohms
in series with a reactance of -15.4 ohms. YO displays asterisks
whenever a value overflows the space provided. Z stands for
impedance. The lambda symbol means wavelengths. The path and
name of the Yagi file appear in the lower-right screen corner.
YO increments the iteration count in the lower-left corner each
time it recalculates element currents; it appends a restart
count during global optimization.
When YO detects an error, it displays an error message
and exits with ERRORLEVEL set to 1. Whenever it invokes NEC, it
sets ERRORLEVEL to 2. Batch files can test ERRORLEVEL.
---- F/B AND F/R -----------------------------------------------
YO uses a generalized notion of standard front-to-back
power ratio to characterize pattern quality. Conventional F/B
is the ratio of forward power (at 0 degrees) to that radiated in
the opposite direction (at 180 degrees). YO's generalized F/B
is the ratio of forward power to that radiated within a
specified region to the rear of the antenna. This is called
front-to-rear ratio (F/R). Yagi designs maximizing conventional
F/B often have large backlobes at angles other than 180 degrees.
Much better patterns result when you optimize a Yagi for F/R.
The F/R region begins at 180 degrees and extends forward to a
specified angle (90 degrees by default). You can define the
forward limit in 5-degree steps and as far forward as 5 degrees.
This wide range lets you control sidelobes as well as backlobes.
During optimization YO uses RMS weighting to combine
backlobe amplitudes within the F/R region. This nonlinear
weighting helps minimize peak backlobes. But reported F/R
figures use the peak backlobe in the F/R region, not the RMS
value. YO samples the radiation pattern in 5-degree steps for
all F/R calculations.
For H-plane patterns of antennas over ground, the F/R
region begins at the rear horizon and ends at the specified
elevation angle. This lets you minimize rear radiation over a
range of elevation angles.
Use the Tradeoffs menu to change the F/R region. Set it
for 180 to 180 degrees (a single point) to obtain conventional
F/B. The F/R value depends on the extent of the F/R region and
on the analysis plane selected.
---- FREQUENCY MENU --------------------------------------------
YO models Yagi designs at a spot frequency or over a
frequency band. Specify a single analysis frequency for spot-
frequency designs, and low, middle, and high frequencies for
designs covering a band.
3
Use the left column to add, change, or delete analysis
frequencies. To switch to a spot-frequency design, enter zero
for the low or high frequency. While spot-frequency designs
optimize much more quickly, the resulting performance often is
unacceptably narrowband.
Use the right column to set the relative weight
(importance) of each frequency during optimization. Nonuniform
weighting can help flatten response across a passband. Press
the = key to reset all weights to 1.
YO-Professional provides two additional analysis
frequencies. This provides tighter control of performance
across a passband, particularly a wide one.
YO models Yagis to 10 GHz. Special tweezers are
available for those of you working with Yagis near the upper end
of this range.
---- HEIGHT MENU -----------------------------------------------
Use the Height menu to specify the height above ground
for a single Yagi, or the free-space, H-plane stacking distance
for two. YO models Yagis over ground as horizontally polarized.
Set height to zero to model in free space. Set stacking
distance to zero to model a single Yagi. YO computes forward
gain, F/R, and the azimuth pattern at the specified elevation
angle.
To maintain accuracy, YO accounts for mutual impedances
between a Yagi and its ground image, and between stacked Yagis.
YO models perfect ground with infinite conductivity and
unity dielectric constant. Yagis over real earth may have
several dB less gain overhead and as much as 1 dB less gain near
the horizon than the figures YO reports. Elevation-pattern
nulls may be less deep. Still, YO can provide useful relative
comparisons among Yagi designs over ground. Use NEC/Yagis to
obtain better absolute accuracy for Yagis over real earth.
---- ELEMENTS MENU ---------------------------------------------
Use the Elements menu to change element positions and
electrical lengths. YO displays half-element length (boom
center to element tip), but you can enter whole-element length
for convenience. Lengths displayed are of electrically
equivalent untapered and boomless elements. These are not
necessarily physical lengths. Use the Taper Schedule menu to
inspect and change physical lengths.
YO can model Yagis with up to 50 elements (70 for YO-
Professional). Press Del to delete the element at the cursor.
Press Ins to add one below it. Use ^Ins or ^Del to avoid
bunching or gaps by automatically respacing elements when adding
4
or deleting. (^ means press Ctrl together with the indicated
key.)
Use the X key to fix or free element position or length
for automatic optimization. The * key fixes or frees all
elements. Use * then X to free just a few. YO highlights fixed
element dimensions with color. The reflector position is fixed
by default since one element position is arbitrary and that of
the reflector least affects performance.
The D key toggles between single and dual driven
elements. YO does not add or delete driven-element mounting
brackets when you use the D key.
Use the ~ key to round element positions or lengths.
Rounding is a good way to test design sensitivity to dimension
tolerances and to generate final dimensions for construction.
Use Undo to undo rounding experiments. (Since YO rounds tip
lengths, untapered-equivalent lengths for tapered designs
normally won't be multiples of the rounding value.)
The = key equalizes all element spacings or lengths
below the cursor. This can provide a reasonable starting point
for optimization. Use Undo to recover from equalization
experiments.
Changing the position of only the last director has a
special effect: All element positions after the last one fixed
change to expand or shrink the design. The entire Yagi scales
if only the reflector position is fixed. This feature is handy
when experimenting with boom length.
YO expects every Yagi to have a reflector element. You
can model a two-element Yagi with driven element and director by
placing a short dummy reflector a great distance away from the
two active elements. This arrangement will satisfy YO while
minimizing modeling errors.
Before accessing the Elements menu, you can select an
element with the left/right arrow keys. The selected element
blinks in the Yagi sketch. When you bring up the Elements menu,
the cursor will be positioned at the selected element. This
feature makes it unnecessary to count elements.
---- ELEMENT TAPERING ------------------------------------------
Fast Yagi-modeling algorithms represent each element as
a thin cylinder of constant diameter. A tapering algorithm
converts elements of tapered telescoping tubing to untapered
cylindrical equivalents. Tapered and untapered elements are
electrically equivalent when their self-impedances are equal.
Tapered elements are physically longer than their untapered
equivalents.
5
YO uses the tapering algorithm developed by Dave Leeson,
W6NL, described in the ARRL book "Physical Design of Yagi
Antennas." This algorithm is based on fundamental principles
and is more accurate than the earlier tapering method developed
by James Lawson, W2PV.
Use the Taper Schedule menu to change taper lengths and
diameters. YO can model up to 20 taper sections per half-
element. Use the Ins and Del keys to add and delete taper
sections. Use the = key to equalize taper lengths below the
cursor. This feature is handy when making wholesale taper
changes. Enter a taper length of zero for elements that don't
employ a particular tubing diameter.
To keep the initial electrical design after making
changes, exit the Taper Schedule menu by pressing K instead of
Esc. YO will adjust element tip lengths to maintain
performance. This feature is handy when mechanically
redesigning a Yagi.
YO does not display untapered-equivalent element
diameters. You can inspect them by saving an untapered AO
output file.
---- MOUNTING BRACKETS -----------------------------------------
A conductive element-to-boom mounting bracket increases
the electrical diameter of an element at the bracket. The
increase depends on bracket size and shape. YO uses the method
of D. Jaggard to model flat, rectangular mounting plates, Hy-
Gain element clamps, L-angle brackets, U-channel brackets,
Cushcraft element saddles, and general brackets of arbitrary
geometry. For details of the method, see "Physical Design of
Yagi Antennas."
Use the Bracket menu to define a mounting bracket.
Select bracket type with the tab key. After you enter bracket
dimensions, YO calculates the length and diameter of an
equivalent taper section. Its length is the half-length of the
bracket (except for Hy-Gain clamps). Its diameter is
electrically equivalent to the tubing and bracket combined.
When you exit the Bracket menu, YO updates the taper schedule
with the new section.
If you enter zero for a bracket dimension (YO lists
"None" for the equivalent taper), when you exit the Bracket menu
YO removes sections that represent mounting brackets from the
taper schedule.
YO creates identical mounting brackets for all elements
but no bracket for insulated driven elements (direct feed,
hairpin match, dual driven elements, Hy-Gain clamps). A bracket
is always represented by the first taper section and its tubing
by the second. To remove a bracket from an individual element,
6
from the Taper Schedule menu add the length of the first taper
section to that of the second, then zero the first.
The length of a mounting bracket is its dimension
parallel to the element. Enter the total length (both sides of
the boom). Width is the dimension parallel to the boom. For
flaring Cushcraft saddles, width is the distance between the
rounded tops (for example, 1" for Cushcraft part number 190156).
Thickness is metal thickness (both halves of a Hy-Gain clamp;
ignore Cushcraft U-bolt backing plates which YO accounts for
itself). Height is the outside-face flange dimension for an
angle bracket, channel bracket, or Cushcraft saddle. YO assumes
that elements touch only one surface of an angle or channel
bracket. The channel-bracket model is accurate for elements
mounted either inside the channel or on the outside surface.
For a general bracket, consider the assembled bracket
and tubing. Enter the cross-sectional perimeter (the distance
an ant would travel when crawling around the assembly) and the
cross-sectional area (the metallic area plus the area of any
fully enclosed spaces). If you can fit the bracket inside a
circle whose circumference is smaller than the bracket
perimeter, enter the circumference instead of the perimeter.
Before defining a Hy-Gain clamp, be sure you've measured
the lengths of the first parasitic-element taper sections from
the centerline of the boom. But measure the first driven-
element taper section from the feedline/hairpin attachment point
since that is the excitation location.
A Hy-Gain clamp electrically passes the element through
the boom. This shortens the clamp's electrical length. Fig. 10
of NBS Technical Note 688 suggests that an HF boom nullifies
about one boom-radius of clamp length. YO therefore subtracts
half the boom radius from taper sections that represent Hy-Gain
half-clamps. See the YO.SET section to change this
compensation.
It's important to account for element mounting when
modeling Yagis. Large mounting brackets can significantly alter
performance. In extreme cases they may move a desired response
completely outside a frequency band. Small brackets can distort
a carefully optimized pattern at a spot frequency. But mounting
methods that use compact hardware little larger than the element
diameter generally require no correction. That's also true for
insulated mounts.
---- BOOM CORRECTION -------------------------------------------
A conductive boom shortens the electrical length of an
element that is close or passes through it.
For through-the-boom element mounting typical of VHF/UHF
Yagis, Ian White, G3SEK, curve-fit measurements by Guenter Hoch,
7
DL6WU, to derive the following boom-correction formula for
noninsulated elements:
C = (12.5975 - 114.5B)B^2
C is the element half-length correction and B is boom
diameter, both in wavelengths. The experimental data for this
formula came from boom diameters smaller than 0.055 wavelength
(1.5" at 432 MHz). YO inhibits entry of larger values. G3SEK
reports that the correction for insulated elements that pass
through a boom with small plastic spacers is close to 50% of C.
YO implements the Hoch-White formula in the Taper
Schedule menu. Press I to define boom diameters in the first
menu column. A separate boom diameter for each element
accomodates tapered booms. For quick data entry for uniform-
diameter booms, press = to equalize boom diameters below the
cursor. Press I to toggle element insulation. To eliminate the
boom, delete the boom column with Del.
W2PV determined that mounting an element on a flat plate
in contact with a boom electrically shortens its length by 6% of
the boom diameter. He states that this small effect diminishes
rapidly as the element is spaced away from the boom, even by a
short distance. Because this correction typically yields a
frequency shift of less than 10 kHz at 28 MHz, YO does not
implement it.
To change boom-correction parameters, see the YO.SET
section.
---- CONDUCTIVITY LOSS -----------------------------------------
YO accounts for ohmic losses in Yagis due to imperfect
element conductivity. Loss normally is small for tubing
elements at HF, but it can be significant for rod elements at
VHF/UHF. To calculate conductor loss, YO accounts for the
sinusoidal element-current distribution, the length and diameter
of taper sections, and the skin effect, which depends on
frequency and material resistivity.
Press C from the Elements menu to select conductor
material. Pick one of the following:
Silver Pure silver
Copper Int'l Annealed Copper Std
6063 6063-T832 aluminum alloy
6061 6061-T6 aluminum alloy
Zinc Pure zinc
Brass Yellow brass (35% zinc)
Steel Stainless steel (type 302)
Note that the volume resistivity of 6061-T6 material is
23% higher than that of 6063-T832 alloy and 51% higher than that
of pure aluminum.
8
Enter a resistivity value to model an unlisted material.
Enter zero to model perfect-conductivity elements. The increase
in forward gain that results is the total conductor loss.
---- PERFORMANCE TRADEOFFS -------------------------------------
Maximizing Yagi forward gain produces the strongest
transmit signal in the forward direction. On receive, it yields
the best signal-to-noise ratio for omnidirectional noise. But
it also results in a narrow beam, a large backlobe, multiple
sidelobes, low input impedance, and small SWR bandwidth. Yagis
optimized for good patterns sacrifice gain, while those favoring
wide SWR bandwidth give up gain and pattern quality.
Because of these inherent tradeoffs, YO is designed to
optimize a combination of forward gain, F/R, SWR, and input
impedance. Use the Tradeoffs menu to select the performance
parameters of interest and their relative importance. Use the
Frequency menu to adjust the relative weight for each frequency.
YO expresses parameter tradeoffs in percent to indicate
relative importance. For example, to maximize forward gain
regardless of the other parameters, set the gain tradeoff to
100%. To maximize gain but also take F/R into account, set the
F/R tradeoff to some nonzero value, say 50%. This tells YO to
weigh both forward gain and F/R when optimizing, and in this
case, to give them roughly equal importance. YO does this by
maximizing a weighted sum of the forward gain and F/R values.
If you allow local optimization to run to completion,
the resulting design will be optimal in the following sense:
Any small design change that improves forward gain will
necessarily reduce F/R. Any F/R improvement will degrade gain.
In other words, there will be no free gain or free F/R to be
had.
In addition to gain and F/R, YO provides SWR and
impedance tradeoffs. You can use the four tradeoffs in any
combination. The SWR tradeoff minimizes SWR. The impedance
tradeoff raises input resistance. This is useful when
maximizing forward gain without F/R or SWR tradeoffs.
When optimizing receiving antennas, select Mismatched
Gain in the Options menu and set the SWR tradeoff to zero.
Power reflected at the antenna terminals, which is reradiated
and lost for receiving antennas, will be subtracted from the
forward gain figure during optimization. This directly accounts
for the effect of SWR on power delivered to the receiver.
Equal values for the gain, F/R, and SWR tradeoffs often
yield a reasonable, balanced Yagi design. (Normally the
impedance tradeoff is unnecessary for multi-frequency designs,
as is the SWR tradeoff for single-frequency designs). The
default tradeoff values (press the = key to restore them)
provide a starting point for custom optimization. Vary the
9
tradeoff percentages according to the relative importance you
place on the design objectives. For example, to emphasize F/R,
increase the F/R tradeoff value. If YO sacrifices too much gain
for SWR, raise the gain tradeoff or lower the SWR tradeoff. By
adjusting the tradeoff percentages, you can home-in on a design
that meets your requirements. The design will be optimal in the
sense that an optimal tradeoff will have been made among the
performance parameters according to the importance you assigned
to each.
---- GOOD-ENOUGH THRESHOLDS ------------------------------------
Sometimes a performance parameter may greatly exceed
your design goal at one or two frequencies. For example, you
might get 35 dB F/R at the top end of a band when all you really
need is 20 dB. Whenever something like this happens, invariably
another parameter is compromised to enable the extra
performance. To address this problem, you might try reducing
the F/R tradeoff. But this will affect all frequencies. You
might reduce the high-frequency weight, but this will affect
gain and SWR as well as F/R.
Good-enough thresholds can help in this situation.
These numbers provide limits beyond which YO does not regard a
performance increase as an improvement. For example, if you set
F/R OK > 20 dB in the Tradeoffs menu, whenever F/R exceeds 20 dB
at any frequency, the optimizer will not regard it as an
improvement. It will have no incentive to increase F/R at that
frequency as long as it stays above 20 dB. This frees the
optimizer to change the design in ways that maximize your other
objectives, such as forward gain. (Good-enough thresholds are
soft limits. They take effect gradually and smoothly near the
limiting values.)
It's best to disable the good-enough thresholds (by
setting them to extreme values) when you first optimize a
design. YO defaults to this condition. Some designs sacrifice
little of one parameter to achieve high performance in another.
If you habitually set good-enough thresholds near tolerable
levels, you'll never uncover these remarkable designs.
Use the tradeoff percentages to apportion optimizer
driving power according to your design priorities. Use the
good-enough thresholds to dynamically redirect that power once
an objective has been met. Because performance characteristics
tend to correlate across a frequency range, good-enough
thresholds cannot completely flatten antenna response. But
often they can help.
---- LOCAL OPTIMIZER -------------------------------------------
YO uses a conjugate-gradient optimizer that combines the
Fletcher-Reeves and Polak-Ribiere methods. It works as follows:
10
First, YO changes each nonfixed element length and
position by a very small amount, with all other dimensions
unchanged, to calculate the sensitivity of the objective to each
variable. The objective is the weighted combination of gain,
F/R, SWR, and impedance defined by your tradeoffs and good-
enough thresholds. The set of element sensitivities is called a
gradient. The gradient is an n-dimensional vector, where n is
the number of nonfixed element lengths and positions. The
gradient points in the direction that locally maximizes the
objective. YO recalculates Yagi response at points along the
gradient until the objective no longer increases. YO then
recalculates the gradient and modifies the search direction.
The new direction incorporates prior gradient information in a
way that minimizes unnecessary iterations. YO repeats this
process until the optimizer can no longer improve the objective.
This optimization technique is robust and efficient,
locating optimal dimensions for an antenna without wild goose
chases in a reasonable number of iterations. However, the
method does not necessarily find the global optimum. The global
optimum is the best possible set of antenna dimensions, where
"best" is defined by your tradeoffs and good-enough thresholds.
The global optimum is missed whenever the algorithm converges to
a local optimum, where small movement in any direction degrades
performance.
Optimization using perturbation techniques is inherently
nearsighted. If you're maximizing forward gain, for example,
and the gain curve has a small bump at a certain set of element
dimensions, the design may wind up on top of the bump because
the algorithm cannot see beyond the immediate vicinity to the
highest point of the overall curve. To visualize the problem,
imagine trying to climb in dense fog to the very top of a
mountain range with multiple peaks. The next section describes
a global solution.
Start the local optimizer by pressing Alt-Z. Press any
key to interrupt it. Interrupting with Esc or a nonfunctional
key causes no further action. Interrupt with a command key to
execute the command.
---- GLOBAL OPTIMIZER ------------------------------------------
When you press Z instead of Alt-Z to start the
optimizer, YO continues optimization after finding a local
optimum. It continues by altering each nonfixed element length
and position by a random amount and then restarting the
conjugate-gradient optimizer. When the optimizer quits, YO
compares the newly optimized performance with the prior result.
If better, as defined by your tradeoff weights and good-enough
thresholds, YO replaces the prior design. If worse, it discards
the new design. YO then generates another random dimension
variation and restarts the local optimizer. This process
continues indefinitely.
11
Global optimization can efficiently locate overlooked
optima. In effect, YO pops an optimized design off its local
peak onto the slope of another and then climbs the slope. The
longer you let it run, the more globally optimal will be the
final result. You can profit from millions of Yagi evaluations.
During global optimization YO normally displays only the
best design so far found. To watch the design trials as they're
being optimized, press W. Leaving YO unattended in watch mode
can slow optimization due to display overhead; press W to toggle
the display mode back to normal. You can abort the global trial
you're watching and move on to the next by pressing X. If your
judgment is good, this can save many iterations. When you're
willing to be attentive, such directed optimization can provide
the best design in the shortest possible time.
The global optimizer uses Gaussian random deviates to
vary element length and position (and for dual-driven designs,
phasing-line impedance). The default standard deviations of 2%
of element length, 20% of average element spacing, and 10% of
phasing-line impedance work well for HF designs. Long-boom VHF/
UHF Yagis typically benefit from a smaller position deviation.
Use the Tradeoffs menu to alter the default values.
YO displays the number of optimizer restarts after the
Yagi count in the lower-left screen corner.
Press Y during optimization to display calculation speed
in Yagis per second. This figure is useful when comparing
processors. The value is an average whose accuracy increases
the longer it's displayed. YO resets the average when global
optimization commences or watch mode changes since these events
alter display overhead. Always use the same Yagi file and menu
settings when comparing speeds. Avoid moving the mouse because
that adds overhead. Press Y to toggle the speed display off.
---- UNDOING CHANGES -------------------------------------------
Whenever you alter a design, YO automatically saves the
design parameters in a last-in, first-out stack. The stack
maintains a history of design changes. Use the Undo command to
recall a previous design. Each press of U moves back one
design. Press Alt-U to move all the way back to the first
design in the stack. Use the Redo command to undo an Undo.
Each press of R moves forward one design, while Alt-R moves all
the way forward to the latest design.
Undo and Redo let you experiment with abandon without
fear of losing a design. They lessen the need to use the Save
command to save intermediate results. They make it easier to
undo manual changes since you don't need to remember parameter
values. Finally, Undo and Redo provide a great way to compare
results before and after optimization, especially when combined
with graph overlays or graph comparison.
12
You can undo and redo within most menus without losing
the menu. This feature is handy when experimenting with
numerical values.
Optimized designs are saved in the stack, but
intermediate designs generated during optimization aren't. If
you change a recalled design, the design history from that point
forward is lost.
---- MATCHING NETWORKS -----------------------------------------
The Match menu lets you design a variety of matching
networks. Use the tab key to select one of the following
network types:
Ideal Match
The ideal match is an idealized, broadband matching
network. It's modeled as a series reactor followed by a
transformer, both lossless and ideal. The optimizer can
minimize SWR while modeling another matching network, but it
won't automatically adjust network parameters. The ideal match
is useful during optimization because YO automatically adjusts
series inductance or capacitance and transformer turns ratio to
minimize SWR. Since the transformer has no reactance and that
of the series component varies little over a band, SWR variation
closely reflects the inherent impedance-bandwidth properties of
the antenna.
When graphing ideal-match SWR versus frequency, YO takes
advantage of the many additional impedance values to refine the
SWR curve. The refined curve shows the lowest weighted SWR
across the passband, using weights linearly interpolated from
the Frequency menu. (YO does not refine SWR for spot-frequency
designs, nor does it update ideal-match component values after
graphing.)
Once you've optimized a design with the ideal match, you
can design a practical matching network. Use graph overlays and
the ideal-match SWR curve as a target when adjusting matching-
network parameters.
Direct Feed
In direct feed the feedline connects to a split driven
element without a matching network. While convenient, Yagis
optimized for direct 50-ohm feed usually perform less well than
matched, low-impedance designs.
You can specify the dimensions of balun leads as well as
the shunt capacitance between driven-element halves. See the
next section for details. Feed spacing is the distance between
balun leads at the driven element.
13
With direct feed you can model a matching scheme once
used for some Mosley Yagis. Add shunt capacitance to raise the
equivalent parallel input resistance. Then lengthen the driven
element to cancel the capacitive reactance. This is the
lowpass, L-network equivalent of a hairpin match.
Hairpin Match
A hairpin match is a highpass L-network that uses
distributed reactances. The shunt hairpin raises the equivalent
parallel input resistance to that of the feedline. A short
driven element cancels the hairpin inductance. A hairpin match
usually is fed with coax through a balun.
YO models the hairpin as a rectangular loop. For
typical hairpin shapes, this model is more accurate than a
shorted transmission line.
You provide hairpin-rod diameter, rod length, and
center-to-center rod spacing. You can also specify the diameter
and length of balun leads. Enter the length of one lead. YO
assumes that the balun leads connect to the driven element at
the hairpin-rod attachment points. Don't neglect to model balun
leads. Even short leads can greatly alter feedpoint impedance.
You can specify shunt capacitance between driven-element
halves. This is particularly useful with Hy-Gain element
clamps. Use 26.5 pF for 20-meter clamps and 9.5 pF for 15- and
10-meter clamps.
Hy-Gain calls its version of the hairpin match a beta
match. The hairpin rods straddle the boom and a shorting strap
connects all three. The boom has a negligible effect on hairpin
inductance, so a beta match is electrically equivalent to a
conventional hairpin match.
YO displays hairpin inductance. Use this value and the
COIL.EXE program to design an air-core inductor to replace the
hairpin. A coil may be more compact, more accessible, and
easier to adjust (squeeze turns).
Gamma Match
YO uses equations by Shintaro Uda and insight by Dave
Leeson to model gamma matches. You specify gamma-rod diameter,
rod length, center-to-center spacing from the driven element,
and series capacitance. To model a lead from gamma rod to coax
connector, specify lead diameter and length.
YO models the strap between gamma rod and element as an
inductive reactance rather than as a short circuit. YO assumes
the strap width plus thickness is equal to the rod diameter plus
1/16".
14
T Match
A T match is a balanced gamma match. Rod length and
capacitance values apply for each side of the driven element.
Some T matches use a 4:1 balun made of a half-wavelength of 50-
ohm coaxial cable. Enter a 200-ohm feed impedance for these
systems, and specify the diameter and length of the lead from
balun to coax connector. Other T-match systems use a 1:1 balun.
Measure lead length from T-rods to balun for these systems. (YO
assumes that lead spacing at the driven element is equal to rod
spacing). To model a T match without capacitors, enter a large
capacitance value (or zero, which YO interprets as infinity).
To model a folded dipole, set the T-match rod length
equal to the driven element length. If the driven element has
just one taper section, YO will keep the rod length equal to the
driven-element length when the latter changes.
Driven-element electrical dimensions vary with T-match
dimensions because the rod fattens the element and acts as a
taper section. Because it's tricky to model this effect, you
may need to adjust driven-element length when constructing a T
match.
--
The impedance value YO reports is always the unmatched
impedance at the center of the driven element. The SWR value is
that in the feedline and includes matching-network effects.
By default YO uses a velocity factor of 0.975 for the
transmission line formed by gamma- or T-match rod and driven
element. To change this value, see the YO.SET section.
Because it affects performance so little (except when
adjacent elements are very close), YO fixes driven-element
length for the ideal match during optimization. YO allows the
length to vary for other matches to help lower SWR. You can
override these defaults with the Elements menu.
For a split driven element (direct feed or hairpin
match), measure the length of the first taper section from the
feedline attachment point since that is the excitation location.
To avoid disrupting special feedpoint tapering, YO does
not add or delete a driven-element mounting bracket when you
switch to another matching network. The Yagi sketch shows which
elements have brackets and can alert you to a problem.
Matching-network performance depends on parameters that
are difficult to measure and to model accurately. Calculated
and actual matches may differ due to input-impedance modeling
error, matching-component geometry simplification, stray
reactances, capacitance-estimation error, lead-length
indeterminacy, proximity of other conductors, and so on. When
15
constructing a Yagi, always make the matching network
adjustable!
Occasionally YO and NEC impedance values may differ
significantly. This can limit accuracy when designing a
matching network. After verifying a design with NEC, access the
Match menu with Alt-M to use NEC impedance values instead of
those calculated by YO. If you change driven-element length
within the Match menu, YO does not invoke NEC to recalculate
impedance. Instead, it uses new YO values compensated by the
difference between prior NEC and YO results. Exit the Match
menu and press the spacebar to verify a compensated-value design
with NEC. To avoid displaying misleading impedance and SWR
curves, YO inhibits the Graphs command within a Match menu
invoked with Alt-M.
---- DUAL DRIVEN ELEMENTS --------------------------------------
YO can model Yagis that use two driven elements
interconnected by a crossed phasing line. This type of feed was
first popularized by KLM Electronics. It is used today on some
Cushcraft and M-Squared Yagis. A dual-driven design may provide
lower SWR across a wide passband. Press D in the Elements menu
to toggle dual drive.
Dual-driven Yagis use balanced feed at the forward
driven element. The nominal feed impedance for KLM designs is
200 ohms, and the antennas use a 4:1 balun to 50-ohm coax.
Phasing-line characteristic impedance varies with antenna model
and line assembly, but it is in the 200- to 250-ohm range for
KLM HF Yagis. YO uses default values of 230 ohms for phasing-
line impedance and 200 ohms for feed impedance. Use the Match
menu to specify other values.
SWR of dual-driven Yagis is sensitive to phasing-line
characteristic impedance. For KLM line construction, the
impedance varies with phasing-line tension. Two insulators
determine line spacing at the center crossover point, but the
spacing elsewhere varies with line tension. This variation
affects average line impedance. Measurement of a 14-MHz KLM
Yagi with a time-domain reflectometer and a vector-impedance
meter yielded an average impedance of 215 ohms when the phasing
line was somewhat slack and 240 ohms when taut.
YO uses a special Match menu for dual-driven Yagis. The
first option allows automatic optimization of phasing-line
impedance. Enable this option when you're willing to modify the
phasing line. The second option maintains constant spacing
between driven elements while allowing their joint position to
vary. This lets you optimize joint driven-element position
without reconstructing the phasing line. The next items specify
phasing-line impedance, feed impedance, and phasing-line
velocity factor. Finally, you can specify balun-lead diameter
and length (one lead), and the spacing between leads at the
driven element.
16
By default YO allows the lengths of dual driven elements
to vary during optimization.
One strategy for optimizing a dual-driven Yagi is to
first optimize the antenna using a nominal phasing-line
impedance of 230 ohms. When you have a good design, save it,
then enable automatic optimization of phasing-line impedance.
Reoptimize to see if significant improvement is possible. Use
global optimization to randomly vary the initial impedance.
To realize optimum SWR characteristics, you should be
prepared to adjust a constructed dual-driven Yagi. The
impedance and velocity factor of your particular phasing line
may differ from the values modeled. It's easy to alter phasing-
line impedance by changing the conductor spacing in the
crossover region. Simply replace the original phasing-line
spacers with ones larger or smaller of your own design.
Experiments have shown that you can raise average line impedance
50 ohms by increasing the crossover spacing to a few inches, or
lower it 50 ohms by decreasing spacing to a fraction of an inch.
It's not necessary to measure the line impedance; simply adjust
conductor spacing until the SWR characteristics match those
predicted by YO. An alternative is to adjust driven-element
lengths for minimum SWR.
Don't neglect to model the flat straps KLM uses to
connect parasitic element halves. The equivalent cylindrical
diameter of a flat strap is half its width. The half-length of
a strap is the distance from the center of the boom to the strap
mounting bolt. Measure tubing length from this bolt rather than
from the tubing end.
Dual driven-element lengths often are short, and
optimized designs may have closely spaced elements. Both of
these factors tend to increase the impedance-modeling error.
Always check SWR for dual-driven designs with NEC.
When YO generates an AO output file for a dual-driven
Yagi, it uses a current source at each driven element rather
than modeling the phasing line with wires. Note that source
magnitudes and phases will not remain strictly valid if you
change the analysis frequency within AO.
---- FREQUENCY SCALING -----------------------------------------
YO can scale a Yagi design to another frequency while
maintaining performance characteristics. This makes it easy to
replicate a design on another band without designing a new
antenna from scratch. The scaled design can use an entirely
different taper schedule.
Scaling can virtually duplicate response at a spot
frequency, but performance across the new and original frequency
bands will differ unless element diameters scale with frequency
and the relative bandwidths are equal. This is unlikely. After
17
scaling a design, reset the low and high frequencies to the new
band edges, check performance, and do a quick touch-up
optimization if necessary.
Frequency scaling in YO does not rely on a simple
polynomial approximation for element self-impedance as does the
W2PV scaling technique, nor does it attempt to match element
reactances. Instead, YO iteratively recalculates element self-
impedance with the method it uses for normal analysis while
adjusting tip length. YO stops when the phase angle of the
complex self-impedance has converged to that of the original
element.
To scale a design, enter new taper diameters and lengths
in the Taper Schedule menu. (Don't bother with tip lengths
since YO will adjust them during scaling.) Press C and enter
the new design frequency. When you press Esc, YO adjusts
element tips to yield a design at the new frequency electrically
equivalent to the design that was current when you brought up
the Taper Schedule menu.
YO does not alter the dimensions of matching networks or
mounting brackets when scaling a design.
---- OUTPUT FILES ----------------------------------------------
Use the Save command to save the current Yagi design in
a file. You can specify a path with the filename. If you enter
the name of a file that already exists, YO asks permission
before overwriting. To quickly save, press Enter without a
filename to overwrite the last file saved (no permission
requested). If no file has been saved, YO writes the design to
SAVE.YAG.
Save follows the YO quick-check convention that pressing
a command key a second time exits a menu (first keystroke only
for Save and Notes). To save a filename beginning with V, press
the spacebar and then enter the filename.
In case you forget to save a design, YO automatically
saves the current design in OUT.YAG when you exit the program.
Recover the design by specifying OUT.YAG as an input file.
Enter PRN or LPT for the output filename to print an
output file. This will record antenna dimensions in a compact,
easy-to-read format along with any design notes.
If you specify the extension .ANT when saving a file, YO
uses the AO file format. YO does not model matching networks or
balun leads in AO output files, but it does normalize element
positions so that the center of the boom is at X = 0. For YO-
format output files, YO normalizes the reflector position to
zero. Output files use current units. See the next section to
control tapering in AO output files.
18
YO 7.5 saves boom, mounting-bracket, matching-network,
and extra-frequency data in output files in such a way that
earlier versions can read the remaining data. (But versions
earlier than 7.0 will always use #12 wire for balun leads and a
velocity factor of 0.975 for transmission lines.)
---- OPTIONS MENU ----------------------------------------------
The Options menu lets you control some additional
aspects of YO.
The E-plane is the plane containing Yagi elements.
Select this plane to optimize the azimuth pattern of a
horizontally polarized Yagi. The H-plane is the plane
perpendicular to the elements. Select this plane to optimize
the azimuth pattern of a vertically polarized Yagi.
YO can account for mismatch loss for receiving antennas.
Mismatch loss is the power reflected at the antenna terminals,
which for receiving antennas is reradiated and lost. When the
option is enabled, the gain figure on the main screen includes
mismatch loss. The loss value itself is displayed following it
in gray. YO includes mismatch loss when graphing, optimizing,
and plotting. Mismatch loss applies to transmitting antennas
only when the source and feedline impedances are close, as for a
laboratory signal generator.
You can disallow longer elements when optimizing an
antenna with nontelescoping elements and you don't want to
fabricate new ones. When combined with fixed element positions,
this option lets you simply trim elements for improved
performance.
When you specify a fixed boom length, YO fixes the
positions of the reflector and last director during
optimization. YO also inhibits changes to these element
positions with the mouse.
YO can generate AO output files with tapered or with
electrically equivalent untapered and boomless elements.
Tapered output normally is best. Use untapered output to
include boom correction or driven-element shortening due to a T
match in AO models, to simplify AO models, or to examine
equivalent taper diameters. YO output files are always tapered
and boomful.
You can control NEC accuracy and execution time by
varying its segmentation density. See NY.DOC for guidance in
setting this parameter.
By default YO uses the dimension units of the Yagi file.
See the YO.SET section to have YO convert file dimensions to the
units specified in the Options menu. Output files use current
units. Wavelength units are based on the wavelength of the
middle analysis frequency.
19
---- ELEMENT-CURRENT PROFILE -----------------------------------
YO draws a profile of element-current magnitudes along
the Yagi sketch. Current is plotted linearly, with zero at the
boom. YO normalizes the profile so that curve height remains
constant from screen to screen. The up-arrow and down-arrow
keys scale the curve. Scaling can bring out small detail or
position the curve for screen printout. You can scale the
profile during optimization without interrupting the optimizer.
To disable the profile, set its color to the background color.
The element-current profile is fascinating to ponder for
its deeper significance, but it has a practical use as well. It
can reveal elements with questionable tuning, particularly for
long-boom Yagis. Elements with abnormally high or low current
are easy to spot in the profile.
YO computes the element-current profile at the middle
analysis frequency.
---- FREQUENCY GRAPHS ------------------------------------------
YO graphs forward gain, F/R, SWR, and impedance curves
versus frequency. Regular command keys are active while viewing
the graphs. For example, press M and G to alternate between the
Match menu and graphs when adjusting a matching network. Press
F1 to list graphs commands.
YO automatically scales the graphs. To generate the
curves, it recalculates Yagi response every two pixels along the
frequency axis. To change this resolution, see the YO.SET
section. The gain curve includes mismatch loss when the option
is selected. The F/R curve reflects the current setting for F/R
region. The impedance curve graphs input resistance. YO graphs
spot-frequency designs over a +/- 0.5% frequency range.
Press F8 to save a graph (the first graph viewed is
automatically saved). Later while viewing another, you can
recall the saved graph for comparison by pressing the spacebar.
The spacebar then switches between the two graphs. Better
still, press O to overlay two graphs. This is a great way to
compare the performance of two designs.
---- PATTERN PLOTS ---------------------------------------------
The pattern sketches YO draws on the main screen omit
grids and scales to reduce screen clutter. For speed, they have
just 5-degree resolution. Use the Plot command to draw high-
resolution patterns with grids, scales, and annotation. YO
calculates the patterns at the middle analysis frequency with
1-degree resolution.
The Plot command generates a plot file and then displays
it. YO saves the patterns in files so you can later review and
20
compare them. A plot file uses the Yagi filename and the
extension .PF. If you plot, change antenna geometry, and press
P again, YO overwrites the plot file with new patterns. If you
press Alt-P, YO generates a new plot file. Each new file has an
incrementing digit appended to its name. Use Alt-P to avoid
overwriting plot files generated earlier in a session.
You can review a plot from the command line by typing YO
PLOT. This bypasses the analysis part of YO and lists plot
files in the current directory. Provide a directory name on the
command line to list its plot files. To display a pattern
immediately, provide the plot-file name on the command line, for
example, YO PLOT HG204BA.
YO generates plot files in the OpenPF plot-file format.
OpenPF is an open, nonproprietary standard for files containing
electromagnetic-field data. See OPENPF.DOC for details. YO
creates OpenPF plot files with phase data for free-space
elevation patterns. These files provide complete elevation data
for use with the TA Terrain Analyzer program. YO centers the
Yagi on the boom when writing a plot file to provide a
consistent phase reference.
YO provides two radial scales for polar plots. The
default ARRL log-dB scale compresses minor lobes toward the
polar center, emphasizing major lobe shape. This scale is
widely used in amateur publications. The center of the plot is
minus-infinity dB on the log-dB scale, but there is little plot
area below -40 dB.
The linear-dB polar scale provides much more area below
-20 dB. It's good for examining minor lobes that may be hard to
see in a log-dB plot. The linear-dB scale cuts off at -50 dB at
the polar center.
YO-Professional provides a third polar scale, one linear
in field strength. This linear scale is useful when comparing
YO plots with those generated by automatic pattern-plotting
equipment on an antenna test range.
See the YO.SET section to use the linear-dB or linear
polar scale by default.
Dots in the sparse radial lines are spaced 2 dB, while
those in the two outer circles are 1 and 2 degrees apart. These
calibrations let you read directivity values from the plots with
good accuracy.
Select rectangular coordinates with the R key. This
coordinate system can reveal minor-lobe detail even better than
can the linear-dB polar plot, but the overall pattern shape
isn't as easy to grasp. The X-axis is degrees off boresight and
the Y-axis is antenna response in dB. Use the Y key to change
the Y-axis cutoff. This parameter is always negative, but you
can enter it without a minus sign for convenience. Change the
21
X-axis cutoff with the X key. The value you enter is rounded to
the nearest multiple of 10 degrees.
Press the O key to overlay two patterns. Annotation
color matches pattern color. YO displays filenames instead of
titles when the titles differ.
Press the C key to compare two patterns. After
selecting a second plot file, press the spacebar to switch
between the two patterns. This is a good way to compare
patterns so complex that an overlay muddles detail.
YO identifies free-space patterns as E-Plane or H-Plane.
It uses the annotations Azimuth or Elevation for over-ground
patterns.
Polar plots are perfectly circular on monitors with
standard 4:3 aspect ratio. Adjust your monitor's vertical-
height control to correct elliptical plots.
---- ARRAYS OF YAGIS -------------------------------------------
Given the pattern of a single antenna, YO can synthesize
the pattern and gain of a rectangular array of Yagis. Since the
synthesis is very fast, you can quickly investigate the
properties of large Yagi arrays.
Press P to plot a single-Yagi pattern. Then press the +
key to increment the antenna count in the plane you're viewing.
Press the - key to decrement the count. Press Enter to switch
to the other plane, and use + and - to set the Yagi count in
that plane.
Vary array spacing with the up/down arrow keys. Use the
Home and End keys for finer resolution and PgUp and PgDn for
coarser. Array spacing varies in the plane you're viewing.
Spacing can differ in the two planes, but all Yagis are
uniformly spaced within a plane. YO uses wavelength spacing
units by default. Press the U key to change to inches or
millimeters.
You can compare the pattern of a synthesized array with
another pattern, but you can't normalize or overlay it. YO
synthesizes free-space patterns only.
YO ignores mutual impedances between individual Yagis
when synthesizing array patterns. For most Yagis, interaction
is small at realistic array spacings. YO uses pattern
integration to estimate array gain. The gain estimate usually
is within a few tenths of a dB of true array gain, and it peaks
at a spacing close to the true gain peak. By varying array
spacing and observing the gain figure and pattern sidelobes, you
can quickly determine the best geometry for a desired gain/
pattern tradeoff. Then you can analyze the array from the
22
command line with NEC/Yagis to account for all mutual
impedances.
---- GAIN FIGURE-OF-MERIT --------------------------------------
For free-space, single-Yagi models, YO estimates the
maximum forward gain practical on the boom length. YO displays
the difference between forward gain and this maximum at each
frequency. This number provides a handy gain figure-of-merit
(FOM) that shows at a glance how close a design comes to
realizing all the gain it can.
To calculate maximum practical gain, YO uses the
following formula:
G = 10Log(5.8B + 3.7)
G is gain in dBd and B is boom length in wavelengths.
The formula yields figures within a couple tenths of a
dB of reasonable expectations for booms as short as 0.4
wavelength. The formula does not estimate maximum possible
gain. That condition leads to very low impedances and extremely
narrowband designs. Instead, the formula predicts the gain of
practical, near-maximum-gain Yagis with real-world losses and
design compromises. Thus, some designs may exhibit a positive
FOM. See the YO.SET section to change the formula coefficients.
The gain FOM is not intended as an overall quality
rating for Yagis. It rates gain/boom-length efficiency only.
Most Yagi applications require good patterns and this constraint
always limits forward gain.
---- MODELING LIMITATIONS --------------------------------------
YO accurately predicts antenna performance as long as
you carefully characterize element tapering and mounting, and
you follow the guidelines in this section.
YO is calibrated to NEC, the Numerical Electromagnetics
Code. YO closely tracks NEC for element diameters up to 0.01
wavelength. Yagis with thicker elements may exhibit some
frequency offset from calculated performance. Still, YO agrees
reasonably well with NEC for diameters up to about 0.04
wavelength. (When comparing YO and NEC results, make sure NEC
has converged. Some NEC models require up to 60 segments/
halfwave for full convergence.)
Models with input impedances of just a few ohms are not
likely to be accurate. At these impedance levels, element
currents are large and fields nearly cancel. This condition
magnifies small model inaccuracies. There are practical reasons
to avoid very low-impedance designs as well: Dimensions become
critical, skin effect may cause excessive loss, impedance
23
matching becomes difficult, and bandwidth can be severely
restricted.
Accuracy may degrade somewhat for designs with half-
elements shorter than 0.19 wavelength or longer than 0.26
wavelength. Such dimensions may occur for very long Yagis, very
wideband designs, or for dual driven elements.
YO may understate SWR at the band edges for Yagis with
very closely spaced elements, particularly more than two such.
Always check SWR-critical designs with NEC.
To prevent gross modeling errors, YO won't let you enter
element half-lengths shorter than 0.15 wavelength or longer than
0.3 wavelength. It won't let you position elements closer than
0.05 wavelength (see the YO.SET section to change this limit).
Finally, it disallows taper diameters greater than 0.05
wavelength.
---- VERIFYING DESIGNS WITH NEC --------------------------------
From the command line you can verify any YO design with
NEC/Yagis by typing NY filename, where filename is a YO file
(the .YAG file extension isn't needed). NEC will report forward
gain, F/R, input impedance, SWR, and losses, and then display
patterns.
To invoke NEC from within YO, press the spacebar. YO
will generate an output file for NEC and exit. The YO.BAT batch
file then takes over, sequencing NEC through an analysis
equivalent to that on the YO screen. When NEC finishes, YO.BAT
restarts YO. YO reloads the output file but displays NEC
performance figures and pattern sketches in place of its own.
Press the spacebar to toggle between NEC and YO results for
comparison. If you alter the design, the spacebar will reinvoke
NEC for an updated analysis. Use the Options menu to set NEC
segmentation density.
NEC generates high-resolution patterns at the middle
analysis frequency. To display them, press P to plot YO
patterns and then overlay or compare the NEC.PF plot file. The
versus-frequency graphs always are YO results, never those of
NEC.
By default, NEC analyzes over-ground antennas using
lossy earth, not perfect-conductivity ground as does YO. Put
GND=0 in YO.SET whenever you need an exact comparison with YO
over-ground results. See NY.DOC for more information about
ground models.
Press Esc to interrupt NEC analysis and return to YO.
24
---- NOTEPAD ---------------------------------------------------
Use the Notes command to enter, edit, and display design
notes. YO displays the Yagi title at the top of the notepad and
you can edit it, too. YO saves the title and notes in all
output files.
The notepad editor automatically wraps words within a
paragraph. A blank line or a line with leading space begins a
new paragraph. Use the arrow keys, Home, End, PgUp, and PgDn to
move the cursor. Press Ctrl with the right or left arrow to
move the cursor to the next or previous word. Del and Backspace
delete characters, Alt-W deletes a word, and Alt-D deletes a
line. See the YO.SET section to redefine the keys for word
delete and line delete.
---- SCREEN ----------------------------------------------------
Press F5 to change the colors of any screen. Use the
left- and right-arrow keys to select a screen item, which blinks
once when selected. Then use the other listed keys to alter the
red, green, and blue color components. When you're done, press
Esc. YO saves color codes in the YO.INI initialization file in
the directory containing YO7.EXE.
YO also saves menu settings in YO.INI each time it
terminates. At the next session, YO initializes its menus to
the saved values, restoring them. To reset everything to
default settings, delete YO.INI.
To export YO graphics, press F9 to save a color image of
any screen in the PCX file format. The output filename is the
Yagi filename with PCX extension. If you press F9 again, YO
appends an incrementing digit to the filename and creates
another file.
YO prints screens to HP LaserJet-compatible printers
(including DeskJets) and to Epson-compatible, dot-matrix
printers. Press PrtSc to print any screen. See the YO.SET
section to configure YO for your particular printer. YO prints
monochrome images only. To print color images, generate a PCX
file and print it with other software.
Except for LaserJet landscape mode, YO does not eject a
page after printing a single screen. This lets you print two
screens on one page (24-pin dot-matrix images are too big to
allow this). YO will automatically eject the page after it
prints a second screen. To manually eject a single-page print,
press F12.
To keep the mouse cursor from appearing in a screen
print, move it beyond the right edge of the screen.
25
---- MOUSE -----------------------------------------------------
You can use a mouse to select Yagi files, but its main
purpose is to let you change antenna geometry and optimization
tradeoffs graphically.
Grab an element at its center to change its position.
Grab it at the top to change its length. To simultaneously
alter position and length, grab an element at the bottom. Press
U to undo mouse changes. You can adjust element dimensions with
the mouse during optimization. This feature is handy for
nudging the optimizer toward a geometry you believe to be
optimum. Grabbing an element during global optimization
activates watch mode.
YO displays a triangle whenever the Main menu
disappears. The vertices of the triangle represent tradeoffs.
The location of the dot within the triangle reflects the current
tradeoff settings. Grab the dot with the mouse and move it to
alter the tradeoffs. When you release the mouse button, YO
starts the global optimizer. Grab the dot during optimization
to change tradeoffs on the fly.
The purpose of the tradeoffs triangle is to provide a
simple, intuitive way to explore Yagi performance space. Simply
move the dot around within the triangle to find the most
attractive design. On a very fast computer, the design
displayed is quickly optimal (locally, at least).
Pressing the right mouse button is like pressing the Esc
key.
---- YO.SET ----------------------------------------------------
The YO.SET file sets YO parameters that aren't changed
often enough to warrant inclusion in YO menus. Use any text
editor to create YO.SET. Put each parameter on a separate line.
Entries can use upper or lower case. YO looks for YO.SET in the
directory containing YO7.EXE.
Directories
Once you accumulate many Yagi and plot files, it's
convenient to organize them into directories. You might use the
current directory for experiments, saving optimized files
elsewhere. YO.SET can tell YO to automatically reference
certain directories. YO uses the directories only for reading
files.
Define directories like this:
YAG=HFBEAMS VHF KLM 50MHZ .
PF=. HFPLOTS 2MPLOTS LONGYAGS
26
The dot represents the current directory. It can appear
anywhere (or nowhere) in a list. You can define as many
directories as you like. You may find it convenient to use the
same set of directories for both Yagi and plot files. You might
organize directories by Yagi type, frequency band, designer, and
so on.
YO (YO PLOT) begins by listing files in the first
directory on the YAG (PF) list. After the files it lists the
names of the other directories. Select one to list its files.
You can specify a file on the command line from one of
the directories without typing its path. YO searches the
directories in the order they appear in the directory list.
You can specify a directory (not necessarily from the
list) on the command line to list its files. To list files in
the current directory when it's not first on the list, type YO .
(YO PLOT .).
Gain Reference
To display gain figures in dBd rather than dBi, do the
following:
DB=dBd
To use dBd in free space and dBi over ground, do this:
DB=dBdi
The gain reference for dBd is the peak gain of a
halfwave dipole in free space. The reference for dBi is the
gain of an isotropic antenna in free space. An isotropic
antenna radiates uniformly in all directions. A dipole has 2.15
dB gain over an isotropic antenna, so YO converts from one gain
reference to the other by adding or subtracting 2.15 dB.
Units
YO normally uses the dimension units of the Yagi file.
To automatically convert file dimensions to the units specified
in the Options menu, do this:
UNITS=MENU
Polar Scale
YO normally uses a log-dB polar scale to display
patterns. You can specify a linear-dB scale as the default with
this:
POLAR=LINDB
27
To specify a linear scale for YO-Professional, do this:
POLAR=LINEAR
Plot Normalization
YO normally scales the low-, middle-, and high-frequency
patterns independently. This gives each plot the same amplitude
in the forward direction, making it easy to compare patterns.
But gain differences aren't apparent. To normalize plots so
that all patterns are drawn to the same scale, do the following:
NORM=ON
Printer Type
YO defaults printed output for HP LaserJet printers in
portrait mode. To try a landscape plot (not available on all
printers), do this:
PINS=HPLJ L
For a bigger landscape plot, add a B:
PINS=HPLJ LB
YO normally draws LaserJet plots with a border. To
eliminate the border, add an X to other options like this:
PINS=HPLJ LBX
YO can transfer compressed data to PCL 5 laser printers
for faster output. To try this, add a C:
PINS=HPLJ LBXC
For an HP DeskJet printer, use the following:
PINS=HPDJ
Add an X to eliminate the border. No other HPLJ options
work.
For a 9-pin dot-matrix printer, do the following:
PINS=9
Some 9-pin printers don't recognize the special line-
spacing command YO uses to reproduce an exact screen image. If
your printer won't print YO screens, try this:
PINS=9ALT
Even with 9ALT, YO may be unable to print to certain old
28
9-pin printers.
For a 24-pin dot-matrix printer, do this:
PINS=24
Printer Port
Output goes to LPT1 by default. For a different port,
use one of the following:
LPT=LPT2
LPT=LPT3
Notepad Delete Keys
Use WDEL and LDEL to redefine the notepad keys for word
delete and line delete. Use ^ to indicate the Ctrl key and Alt-
to indicate the Alt key in combination with a letter key. You
can also use ^Enter and ^Bksp. Use F1 through F10 for function
keys. For example:
LDEL=^Y
LDEL=F3
WDEL=Alt-K
WDEL=^Bksp
Graph Resolution
When graphing performance versus frequency, YO
recalculates Yagi response every two pixels. You can trade
resolution for speed by changing the number of pixels per
frequency step with the following:
PIX=number
Minimum Element Spacing
YO normally won't position elements closer than 0.05
wavelength. To change the spacing limit, do this:
MINSP=spacing
Accuracy may degrade when elements are very close. Use
a setting below 0.05 wavelength only when you're willing to
frequently check results with NEC.
29
Gamma/T Velocity Factor
By default YO uses a velocity factor of 0.975 for the
transmission line formed by a gamma- or T-match rod and driven
element. To change this value, do the following:
VEL=value
Use the Match menu to set the phasing-line velocity
factor for a dual-driven design.
Gain Figure-of-Merit
To change coefficients of the gain figure-of-merit
formula, do the following:
FOM=a b
The formula is G = 10Log(aB + b), where G is maximum-
practical gain in dBd and B is boom length in wavelengths. When
FOM isn't defined, YO uses a = 5.8 and b = 3.7 by default.
To disable the FOM display, do this:
FOM=0
Boom Correction
To model through-the-boom element mounting, YO uses a
formula of the following form:
C = (a + bB)B^2
C is half-element shortening and B is boom diameter,
both in wavelengths. Default values are a = 12.5975 and b =
-114.5. To change these coefficients, do the following:
BOOM=a b c d e
Parameter c is the maximum value of B for which the
formula is valid. Parameter d is the percentage of C to apply
for insulated elements. Parameter e is the percentage of boom
diameter to shorten a Hy-Gain clamp to account for boom
proximity. Default values are c = 0.055, d = 50, and e = 50.
VESA BIOS Extension
YO uses the VESA BIOS Extension (VBE) for smooth screen
animation. VBE may be included in your VGA card's video BIOS,
it may be provided as an optional file, or it may not be
implemented at all. YO automatically detects VBE. It displays
"No VBE" on the file screen when it can't find it, and
"Incompatible VBE" when VBE is present but unusable. YO can't
30
always determine that a VBE implementation is incompatible. If
your YO screens look or act funny, or if YO won't even execute,
try inhibiting VBE with this:
VBE=NO
YO displays "VBE ignored" to confirm.
31
INDEX
# key 2
* key 5
+ key 22
- key 22
.ANT 18
.INI 25
.SET 26
.YAG 1, 24
180 to 180 degrees 3
1:1 balun 15
200-ohm feed 15
4:1 balun 15, 16
50-ohm feed 13
6061-T6 8
6063-T832 8
= key 4, 5, 6, 9
^Del 4
^Ins 4
~ key 5
Accuracy 1, 4, 19, 21, 24
Alt-D 25
Alt-M 16
Alt-P 21
Alt-R 12
Alt-U 12
Alt-W 25
Alt-Z 11
Aluminum 8
Always make the matching network adjustable! 15
Analysis plane 3
AO output file 6, 17, 18, 19
Array gain 22
Arrays of Yagis 22
ARRL 6, 21
Arrow key 1, 2, 5, 22, 25
Assembly language 1
Asterisks 3
Automatic optimization of phasing-line impedance 16, 17
Azimuth 22
Backlobes 3
Backspace 25
Balun 14
Balun leads 13
Batch file 3, 24
Beta match 14
Blink 5, 25
Boom Correction 7, 30
Boom length 23, 30
BOOM= 30
Bracket menu 6
32
Brackets of arbitrary geometry 6
Brass 8
C 18
Calculation speed 12
Clamps 14
Coefficients 23
COIL.EXE 14
Color 25
Command key 11
Command line 1, 27
Compare two patterns 22
Comparing processors 12
Comparing YO and NEC results 23
Complex self-impedance 18
Conductive boom 7
Conductivity Loss 8
Conjugate-gradient optimizer 10
Constant spacing between driven elements 16
Convert file dimensions 27
Copper 8
Count elements 5
Crossover spacing 17
Ctrl 4, 25
Current 20
Current directory 1, 26
Current profile 20
Current source 17
Cursor 2, 5, 25
Cushcraft element saddles 6
Cylindrical equivalents 5
D key 5
DB= 27
DBd 27
DBdi 27
DBi 27
Default 2, 3, 5, 9, 10, 12, 15, 16, 19, 21, 22, 24, 25, 27, 29, 30
Del 4, 25
Design sensitivity 5
DeskJet 25, 28
Dev 12
Dimension tolerances 5
Dipole 27
Direct Feed 13
Directed optimization 12
Directories 26
Directory 1, 21
Directory list 27
Disable the good-enough thresholds 10
Disable the profile 20
Disallow longer elements 19
DL6WU 7
Dot 26
Dot-matrix printers 25
Down-arrow 20
33
Dual driven elements 5, 16
Dummy reflector 5
E-plane 19, 22
Earlier versions 19
Earth 4
Eject 25
Element currents 3
Element reactances 18
Element Tapering 5
Element-current distribution 8
Element-Current Profile 20
Elements 29
Elements Menu 4
Elements with questionable tuning 20
Elevation 22
Elevation angle 2, 4
Elliptical plots 22
End 1, 22, 25
Enter 1, 2, 18
Epson-compatible 25
Equivalent cylindrical diameter of a flat strap 17
Erase the Main menu 2
Erase the tradeoffs triangle 2
Error 3, 5, 15, 24
ERRORLEVEL 3
Esc 2, 6, 11, 18, 24, 25, 26
Expand or shrink the design 5
Experiment 2, 5, 26
F/B 3
F/R 3, 9
F/R region 3, 20
F/R tradeoff 9
F1 2
F12 25
F5 25
F8 20
F9 25
Feed impedance 16
Feed spacing 13
Feedline 14
Field strength 21
Figure-of-merit 23, 30
Filename beginning with V 18
Final dimensions 5
Fixed boom length 19
Fixed element dimensions 5
Flat, rectangular mounting plates 6
Fletcher-Reeves 10
Folded dipole 15
FOM 2, 23
FOM= 30
Forward gain 1, 9
Fractional data 2
Free space 4
34
Frequency band 3
Frequency Graphs 20
Frequency Menu 3
Frequency range 20
Frequency Scaling 17
Front-to-back 3
G3SEK 7
Gain figure-of-merit 2, 23, 30
Gain FOM 23
Gain Reference 27
Gain tradeoff 9
Gain/boom-length efficiency 23
Gain/pattern tradeoff 22
Gamma Match 14
Generalized F/B 3
Global Optimizer 11
GND= 24
Good-Enough Thresholds 10
Gradient 11
Graph Resolution 29
Gray 19
Ground 4
H-plane 3, 19, 22
Hairpin inductance 14
Hairpin Match 14
Handy 2, 5, 6, 13, 23, 26
Height Menu 4
HF Yagis 16
High-resolution patterns 20
Highlight 1, 5
History of design changes 12
Hoch 7
Hoch-White formula 8
Home 1, 22, 25
Hy-Gain element clamps 6, 14
Ideal match 13
Impedance 3, 20, 23
Impedance tradeoff 9
Impedance value 15
Inches 22
Ins 4
Insulated elements 8
Intermediate designs 13
Interprets as infinity 15
Interrupt NEC 24
Isotropic antenna 27
Iteration count 3
Jaggard 6
James Lawson 6
35
K 6
Keep the initial electrical design 6
KLM 16
L-angle brackets 6
L-network 14
Lambda symbol 3
LaserJet 25, 28
LDEL= 29
Lead-length indeterminacy 15
Leeson 6, 14
Lightbar 1
Line delete 25, 29
Linear scale 21
Linear-dB polar scale 21
Listing files 27
Local Optimizer 10
Log-dB scale 21
Long-boom Yagis 20
Lossy earth 24
Low impedances 23
LPT 18, 29
LPT= 29
Main menu 2
Match menu 13, 16
Matching Networks 13
Maximum forward gain 23
Maximum practical gain 23
Menu settings 25
Millimeters 22
Minimum Element Spacing 29
MININEC 1
MINSP= 29
Mismatch loss 2, 19, 20
Modeling Limitations 23
Mosley Yagis 14
Mounting Brackets 6
Mouse 1, 26
Mouse cursor 25
Mutual impedance 4, 22
NBS Technical Note 688 7
NEC 1, 19, 23, 24
NEC.PF 24
NEC/Yagis 4, 22, 24
Network 13
Nonfunctional key 2
Nontelescoping elements 19
NORM= 28
Normalize plots 28
Notepad 25
Notepad Delete Keys 29
Notes 25
Numerical Electromagnetics Code 1, 23
NY.DOC 19, 24
36
Objective 11
Ohmic losses 8
Omnidirectional noise 9
OpenPF plot-file format 21
Optimize joint driven-element position 16
Optimum SWR characteristics 17
Options Menu 19
Other 1
OUT.YAG 18
Output filename 18
Output Files 18, 19, 25
Overlay two patterns 22
Parameter tradeoffs 9
Path 27
Pattern integration 22
Pattern Plots 20
PCX 25
Peak backlobes 3
Pentium processors 1
Percent 9
Perfect ground 4
Perfect-conductivity elements 9
Perfect-conductivity ground 24
PF 21
PF= 26
PgDn 1, 22, 25
PgUp 1, 22, 25
Phase data 21
Phasing line 16
Phasing-line tension 16
Physical Design of Yagi Antennas 6
PINS= 28
PIX= 29
Pixels per frequency step 29
Plane 22
Plot file 20, 26
Plot Normalization 28
Polak-Ribiere 10
Polar scale 27
POLAR= 28
Power 3
Print an output file 18
Print any screen 25
Printer Port 29
Printer Type 28
PRN 18
Profile 20
Proximity of other conductors 15
PrtSc 25
Quick check 2
Quick-check convention 18
Radial scales 21
Random deviates 12
37
Random dimension variation 11
Randomly vary the initial impedance 17
Reactance 14
Real earth 4
Rear horizon 3
Recall a previous design 12
Receiving antennas 9, 19
Rectangular array 22
Redo 12
Resistance 9
Resistivity 8
Resolution 22
Respacing elements 4
Restart count 3
Right mouse button 26
RMS weighting 3
Rounding 5
Save a graph 20
Save and Notes 2, 18
SAVE.YAG 18
Scale 17, 28
Screen 25
Screens look or act funny 31
Segmentation density 19
Self-impedance 5, 18
Shunt capacitance 14
Sidelobes 3
Signal-to-noise ratio 9
Silver 8
Sketch 5, 15, 20
Skin effect 23
Soft limits 10
Source magnitudes and phases 17
Spacebar 2, 18, 20, 22, 24
Spacing limit 29
Speed display 12
Spot frequency 3, 17
Spot-frequency designs 20
Stack 12
Stacking distance 4
Stainless steel 8
Standard deviations 12
Strap 14, 17
Strategy for optimizing a dual-driven Yagi 17
Stray reactances 15
SWR 9
SWR bandwidth 9
SWR for dual-driven designs 17
SWR value 15
Synthesize 22
T Match 15
TA Terrain Analyzer 21
Tab key 6, 13
Taper Schedule menu 6
38
Tapering algorithm 5
Through-the-boom element mounting 7
Tip length 18
Title 25
Total conductor loss 9
Tradeoff percentages 10
Tradeoffs 9
Tradeoffs menu 3, 9, 10, 12
Tradeoffs triangle 26
Triangle 26
Tweezers 4
Two-element Yagi with driven element and director 5
U key 22
U-channel brackets 6
Uda 14
Undo 12
Units 18, 19, 22, 27
UNITS= 27
Untapered and boomless elements 19
Untapered-equivalent element diameters 6
Untapered-equivalent lengths 5
Up-arrow 20
Using YO 1
VBE 30
VBE= 31
VEL= 30
Velocity factor 15, 16, 17, 19, 30
Verifying Designs with NEC 24
VESA BIOS Extension 30
VHF/UHF 7, 8, 12
W 12
W2PV 1, 6, 8, 18
W6NL 6
Watch the design trials 12
Wavelength 22
Wavelength units 19
WDEL= 29
Weighted sum 9
Weights 4
White 7
Whole-element length 4
Wild goose chase 11
Wire gauge 2
Word delete 25, 29
Wraps words 25
X 12
X key 5
X-axis cutoff 21
Y 12
Y-axis cutoff 21
YAG= 26
39
Yagi files 1
Yagi performance space 26
Yagis per second 12
YO PLOT 21
YO-Professional 4, 21, 28
YO.BAT 24
YO.INI 25
YO.SET 26
YO7.EXE 25, 26
Z 3, 11
Zinc 8
40
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