Antennas for Field Day• Optimize Kite C-pole • Build a 80-40-20 triband coupled resonator •...
Transcript of Antennas for Field Day• Optimize Kite C-pole • Build a 80-40-20 triband coupled resonator •...
Antennas for Field DayA few thoughts….
N6QAD
February 15 2019
Characteristics of the ideal antenna system for FD
2
• Talk to operators across USA
• on all HAM bands except 60m, 30m, 17m, 12m
• within the power budget of the chosen class
• across a time period of 24hrs
• operating as in an emergency situation
Objectives:
Characteristics of the ideal antenna system for FD
3
• Some would argue that since we are lazy we want to do it with:
• Minimum set of antennas (ideally same as the class number)
• Lightweight
• Easy and safe to deploy
Characteristics of the ideal antenna system for FD
4
• Some other would argue that since we are geeks we
want to do it with:
• Maximum number of cool large antennas (sky is the limit )
• Don’t care if we have to put up and tear down 13 towers in 2 days
• The more complex it is, the better
Characteristics of the ideal antenna system for FD
5
• Then there’s us:
• Somehow cool antennas
• Compatible with an emergency situation
• Somehow easy and safe to deploy
HAMs population distribution
Link to map generator
Characteristics of the ideal antenna system for FD
7
• Multiband antenna
• Most of the Gain at 75 degrees
• With a relatively low take off angle 30-20 degrees
What are the most used antennas for field day?
8
Truth is….pretty much anything! ……. But mostly
• Verticals, Wire Dipoles, Yagis
We have been using (in the last 2 years):
• Hustler 6BT Vertical
• Off-Center Fed Dipoles,
• Hexbeam (Spider beam)
• Sloper Dipole
• Coupled resonator dipole
Trap Vertical - Hustler 6BTV
9
• Multiband 80-6
• L = 24’
• Easy to deploy (< 30min.)
• Complex radial system - area
• Lack of directivity
Off-Center Fed Dipole
10
• Multiband 80-40-20-10
• L~λ/2 = 135’
• Easy to deploy (2 mast)
• Lack of directivity
Efficiency can be improved by center loading
Hexbeam
11
• Multiband 20-15-10
• Easy to deploy (2 mast)
• Directional and with a decent
take off angle
Sloper Dipole
12
• Single Band
• L~λ/2 = 135’
• Easy to deploy (1 mast)
• Lack of directivity - but
Can we turn it into a Multiband Sloper Doublet?
Vertical 45 degrees Horizontal
Coupled Resonator Dipole
13
• Multiband 20-15-10
• Easy to deploy (2 mast)
• Bidirectional
• Simpler than a Fan or a Trap Dipole
• Easy to operate than a Doublet
• More efficient than an OCFD
QST
June 2017
14
Coupled Resonator Dipole 80-40-20
Other things we have that needs some tweaking
15
Maypole• 4 / 2 band Inverted Vee
• Multiband 80-40-20-15-10
• Easy to deploy (1 mast)
• Bidirectional
16
Other things we have that needs some tweaking
Sloped Delta Loop• Multiband 80-40-20-15-10
• Easy to deploy (1 mast + 2 short)
• Directional
• It’s big! but big antennas big signals
Potential projects before Field Day
17
• Revamp Hustler and Hexbeam
• Optimize Delta Loop
• Optimize 80-40-20-10 Maypole
• Optimize Kite C-pole
• Build a 80-40-20 triband coupled
resonator
• Build a Center Loaded OCFD
• Build a Sloper doublet
Conclusion:
what we have used so far works. What can we add
to the pool and maybe use at FD?
Wire loop AntennasMultiband 80m-6m
N6QAD
January 23rd 2019
Characteristics
19
• Full wave horizontal loop
• Omni-directional
• Multiband
• Resonant on even
harmonics
• For best performance
• Horizontal position
• Height ~40ft
• Maximum area (circle is
best but square or triangle
work)
Length:
Lfeet=1005/fMHz(empirical. should be 984)
Skywire Loop
Sloped Delta loop
20
Area of Loop = Efficiency
• The goal is to get the greatest area inside the loop.
• A circle is the perfect shape, but difficult to build for HF.
• Both Triangles and Rectangles are good performers.
• A Sloped Delta Loop uses a single support on an equilateral triangle.
100%
79%
50-75%
60%
Feed pointFeed point
~ Horizontally polarized Vertically polarized
Variant: Sloped Delta Loop
21
Military Mast
~ 29ft
~ 8ft
Stakes
Sloped Delta Loop: model
22
(x1,y1,z1)
~ 8ft
~ 8ft
d
hp
L
LL
(x3,y3,z3)
(x2,y2,z2)
Mh=29’
d=21’
h=L*sqrt(3/4)
hp=sqrt(h^2-d^2))
Sd=Mh/d*sqrt(L^2-d^2)
h
x1=(hp-L/2)*cos(π/4)
y1=(hp+L/2)*cos(π/4)
z1=Mh-d
x2=(hp+L/2)*cos(π/4)
y2=(hp-L/2)*cos(π/4)
z2=Mh-d
x3=0
y3=0
z3=Mh
Sd
Mh= mast
4nec2 settings
23
Lsidenom=93.7’
Lsideopt=93’
SWR and Input Impedance
24
80m 40m 30m 20m 17m 15m 12m 10m
Typical resistance at the feed point in the HF bands is between 150-300 ohm
- Tunable with an AT after a 4:1 Balun
80m Radiation Patterns – Top fed
25Horz. Pol. Ver. Pol.
40m Radiation Patterns – Top fed
26Horz. Pol. Ver. Pol.
20m Radiation Patterns – Top fed
27Horz. Pol. Ver. Pol.
15m Radiation Patterns – Top fed
28Horz. Pol. Ver. Pol.
10m Radiation Patterns – Top fed
29Horz. Pol. Ver. Pol.
80m Radiation Patterns – Side Fed
30Horz. Pol. Ver. Pol.
Feed Line
31
Typical resistance at the feed point in the HF bands is between 150-300 ohm
Ladder Line:
Z0=450ohm
• Best length = 43’ or 86’
far from an odd multiple of λ/4 at all wavelength of interest otherwise
impedance grows
• This length keeps the impedance at the end of the line between 300-500 ohm
• Tunable with a 1:1 or 4:1 current Balun and an AT
Adding the feed line
32
Construction
33
Materials
• 285’ 12 AWG THHN wire
(5’ extra to allow for
optimization)
• 4 insulators (2 extra in case
we want to turn it into a
square and or feed at the
side)
• 43’ 450ohm ladder line
• 1 ladder line to wire connector
• 6 metal rings
• 1 quick link
• 2 ¼” hooks
• 85’ Paracord
Construction
34
Installation
35
Measurements
36
It was too cold…..
Next Time