Radial less [Compatibility Mod · PDF file“Radial-Less” Verticals R8 Example 8...

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Radial-Less Verticals
Presented by: Keith Witney VE7KW
Radial-Less == Ground-screen independent
Vertical Theory
NSARC HF Operators 110/25/2012
Vertical Theory Pattern, Effect of ground
Radial-less verticals Vertical dipoles, 43 flag poles, Counterpoise, E-H
R8 example Theory, Model, Measured

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Vertical Theory
Perfect vertical
Effect of ground
Radials
Counterpoise Counterpoise
Inductive loading
Capacitive loading
Traps
Stubs

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Vertical Theory
Perfect ground and effect of real groundReal Ground effect matters out to 100Near field ground (1 ) == lossesFar field ground == vertical pattern
Vertical over ideal ground

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Vertical Theory
Vertical patternchanges withlength of verticalmonopolemonopole
14 = -.28dBi at 25
38 = -.20dBi at 25
58 = 1.85dBi at 15

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Vertical Theory
/4 Z= 36Z ~ 50 real Gnd
3/8 Z=196 + j310 /2 Z=~1200-j160End fed vert. dipole
Higher Z helps with counterpoise/efficiencyLifting current maximum helps with efficiency /Gain (5.83 vs 5.15 dBi)

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Vertical Theory
Efficiency = Rrad/(Rrad+Rloss)
Rrad=1450 h^2/^2
/4 = 36.6 ohms
3/8 = 62 ohms
/2 = 69.2 ohms /2 = 69.2 ohms
Rloss
Conductor R
Ground R (15)
Coil resistance (1)
Capacitance loss

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Vertical Theory
Radials: Elevated and/or Buried
Vertical antennas take up as much or more roomthan dipoles when the radials are considered.
Elevated radials Elevated radials should be resonant (on all bands!) . Should be 1/10 above
ground (can angle up)
One will balance current, 2 will balance horizontal patterneffect, more couple to real ground more effectively
Buried Radials need to be dense but can be non-resonant and shorter. Target is L>3/8 and a density at the end of

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Vertical Theory
More radials cangive 3 dB for a lotof metal and space
80m and up 80m and upprobably easier togo multiple dipolesin the same space

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Vertical Theory
Counterpoise consists of a network of wires or cables (or a metal
screen) parallel to the ground, suspended from a fewcentimetres to several metres above the ground, underthe antenna.the antenna.
the counterpoise functions as one plate of a largecapacitor, with the conductive layers of the earth actingas the other. Capacitance increases with plate area andsmaller plate spacing
the counterpoise functions as a RF ground connection
Placed at high impedance points
A common mode choke is required

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Vertical Theory
Near Field is 40m in the city?
Far Field effects ground reflections for low-angle Far Field effects ground reflections for low-anglesignals out to 100 (8 km at 80m)
Applies for all types of antennas

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Vertical Theory
Short Antennas are capacitive so inductive loadingcompensates
Inductive loading Losses related to Coil Q: Losses related to Coil Q:
Large, low R coils

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Vertical Theory
However we might want to go to a longer antennawhich would be inductive
Capacitive loading No R so low loss No R so low loss
Can be disc/wires

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Vertical Theory
We need to isolate unused portions of the antennato make it work on multiple bands
Traps Isolating trap to remove unwanted parts of the antenna Isolating trap to remove unwanted parts of the antenna
Shortening/lengthening traps
Trap frequency is set to geometric mean of the twofrequencies desired
Acts an a lengthening inductor below the trap frequency
Acts as a shortening capacitor above the trap frequency
Traps tend to have losses associated with the coils andcapacitors and can be bulky

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Vertical Theory
Stubs Provide a low loss, high Q means of isolation
Transmission line normally open /4
This creates a high impedance at the end of the stub forthe frequency to which it is tuned effectively adding thethe frequency to which it is tuned effectively adding thestub to the point to which it is attached by creating a lowimpedance at this point and isolating everything else.
In radial-less verticals typical results in a OCF radiator

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Examples
Vertical Dipole
Flag Pole
Non-ground referenced (Counterpoise)
E-H Antennas E-H Antennas

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Radial-Less VerticalsExamples Vertical Dipole
Note the significant effect of ground quality (not only verticals)Elevation above ground can be several metres higher than soil

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Radial-Less VerticalsExamples Vertical Dipole
Force 12 Sigma 5
5 band 20 - 10m
40m 80m 160 m monoband
Note the Sea Water!

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Radial-Less VerticalsExamples 43 ft FlagPole
Or 21.5 if you dont want 80m
This is NOT a resonant antenna. A 10:1 antenna tuner is required.
The tuner need not be remote if coax run is reasonably The tuner need not be remote if coax run is reasonablyshort and good quality coax is used
A common mode choke is required
You must do something about ground losses Multi-band radials but more likely an extensive buried
ground system
Stucco mesh under the grass? (Circulating currents?)
14 lambda to18 lambda. Can be shorter when buried.

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Radial-Less VerticalsExamples 43 ft FlagPole

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Radial-Less VerticalsExample 21 ft FlagPole
10ft by 20 ft stucco mesh2, 10m wires along fence and around garage

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Radial-Less VerticalsExamples Counterpoise
Top fed to move currentmax up
Linear decoupling stubs >20m
Counterpoise at top to Counterpoise at top toincrease current maximumheight above ground
2m /4 vertical above CP!
Base (Top) loaded for30,40,80m
Capacitive hat OCF to theside?

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Titan DX
Vertical Dipole fedat 5/8 point
Cross coupled Cross coupledtuning rods,
coaxial stubs andtuning capacitor
Loop extension for40m

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R5

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AV640
Computer optimized 38
End fed, No traps; stubs 6,10,12,17m
15m center radiator 15m center radiatorterminated with C hat?
Top loading coils (//) withCapacitive hats 20,30,40m
72 CP, 4:1 transformer and1:1 current Balun

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DX77
Off-center-fed dipole
Traps for each band
Where is the OCF? Where is the OCF?

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Radial-Less VerticalsExamples E/H Antennas
Concept is togenerate E and Hfields at the samepointpoint
Isotron (40 & 80m)
WineGlass (2-8MHz)

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Examples Counterpoise
From: HF Vertical Tests Champion Radio N0AX K7LXC 2000Measured Values to 1/4 GP antenna on the same ground mat.Transmit to a small loop and calibrated laboratory receiver at 171m.

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Radial less [Compatibility Mod · PDF file“Radial-Less” Verticals R8 Example 8...

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