Antennas for Field DayA few thoughts….

N6QAD

February 15 2019

Characteristics of the ideal antenna system for FD

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• 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

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• 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

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• 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

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• 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

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• 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?

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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

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• Multiband 80-6

• L = 24’

• Easy to deploy (< 30min.)

• Complex radial system - area

• Lack of directivity

Off-Center Fed Dipole

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• 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

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• Multiband 20-15-10

• Easy to deploy (2 mast)

• Directional and with a decent

take off angle

Sloper Dipole

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• 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

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• 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

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Coupled Resonator Dipole 80-40-20

Other things we have that needs some tweaking

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Maypole• 4 / 2 band Inverted Vee

• Multiband 80-40-20-15-10

• Easy to deploy (1 mast)

• Bidirectional

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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

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• 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

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• 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

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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

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Military Mast

~ 29ft

~ 8ft

Stakes

Sloped Delta Loop: model

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(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

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Lsidenom=93.7’

Lsideopt=93’

SWR and Input Impedance

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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

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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

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Construction

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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

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Installation

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Measurements

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It was too cold…..

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