Memoirs of DXCC

Joe Horanzy AA3JHApril 4th, 2013 K3DN Presentation

Agenda

• Awards

• Impedance

• Measuring Equipment

• Picking the Antenna

• Antenna components with construction tips and theory

• Putting it all together

• Multiband

• Getting more gain

• Simulation tools

• Vertical Moxon

• Future plans

Awards

10 meter progressOpen to all license classes

Impedance

Z = R + jX

Where R = natural antenna and grd loss resistance X = total antenna reactance combination

of capacitance and inductance

Reactance (X) is your enemy. Why?

A reactive component alternately absorbs energy from the circuit and then returns energy to the circuit. A pure reactance will not dissipate any power.

Impedance

You can’t go by just impedance (Z) alone.

A Z of 50 of resistance vs. a Z of 50 reactance is very different.

A Z of 50 of pure resistance = SWR 1:1

A Z of 50 of reactance = SWR >20:1 !

A Z of 100 of pure resistance = SWR 2:1

A Z of 100 of reactance = SWR >20:1 !

Impedance

“So I have residual reactance, so what? I’ll tune it out with my trusty antenna tuner in the shack.”

#1 Remove all reactance at the antenna. Matching at the transceiver only satisfies the connection

between the transceiver and the tuner.

Loss in the cable dramatically increases

Impedance

Measuring Equipment

Picking the antenna

Simple Low maintenance Ease of construction Readily available components Stealth Low cost But very efficient and effective.

Main Object: Get on HF to communicate around the world (DX) with an antenna that is:

The Vertical Antenna

• Few components, low cost.

• Easy to hide.

• Easy to make multiband.

• Has low take off angle, great for DX

• DX is not line of sight. Polarization doesn’t matter.

• Vertical dipoles: don’t need ground radials but is ½ l and end fed requires matching.

• ¼ wave vertical: only ¼ l high (half the V/D height), no balun required, but requires ground radials.

The ¼ Wave VerticalThey get a bad name because many don’t radiate from improper installation from:

Ineffective ground plane / counterpoise Residual reactance, not resonating. Improper trap design causing excess loss.

Anytime you move from the basic antenna, there will always be compromises either through power loss and/or bandwidth limitations.

The ¼ Wave Vertical

The ¼ Wave VerticalSingle Band

1. How high:

*235/ Freq (Mhz)

example: for 14.1 Mhz 20 meter band235 / 14.1 = 16.7 feet.

*235 is from: 300 M meter/sec (speed of light) X 95% (speed of light slows down in wire) /4 (1/4 wave) X 3.3 ft/m (convert to ft)

The ¼ Wave VerticalGround system

2. How many ground radials why? Soil has high resistance. To reduce ground resistance as much as possible. Any power that is dissipated in the soil weakens the signal.

As they say: heating up the worms

From Arrl Antenna handbook

Ground loss

Rg: Ground resistance

Rr: Radiated resistance

Rr: Antenna’s natural radiations resistance: is the virtual resistance in transferring the energy to produce the radio wave.For ¼ wave vertical antennas, it’s about 36 ohms. (note: SWR 1:4)

Rg: Ground loss resistance.

Rtotal = Rr + Rg Z = Rtotal + jX

Antenna efficiency (%) = (Rr / Rtotal ) x 100

For example: say ground resistance is 14 ohm, then

Rtotal = 36 + 14 = 50 ohms, great SWR but…

Efficiency = 36/50 x 100 = 72 percent

If 100 W is transmitted only 72 watts is being radiated.From Arrl Antenna handbook

xmit

Ground radials

The ¼ Wave Vertical

2. Ground radials length:.25 l or greater. For multiband, use random lengths.

3. Wire size:12 or 14 AWG

4: Type:Stranded for vertical Solid for ground radials

5: Insulated: Doesn’t matter.

OR

COMPONENTS

Putting it all together

20M trap

Bungee cord

Ground Connection

Ground Connection

Close up

Multiband VerticalResonate Traps:

Trap:Inductor/HV Cap

Multiband VerticalAnother approach

Fan Vertical

Contacts made with home brew fan vertical antenna (40 to 10 meter)

No amplifier.

• Cancel out all reactance at the antenna.

• Install best ground radials as possible to keep ground resistance low as possible.

• Keep all component loss in the system to a minimal.

• Use good coax, RG213 or better, and ensure all connections are soldered correctly (beware of HRO).

Summary

GainDbi : Gain measured in relation to an isotropic radiator, an imaginary antenna in freespace.Dbd : is a reference to a dipole antenna in free space and is simply Dbi - 2.15Dipole in freespace can have 2.15 Dbi gain or 0 Dbd.

From Arrl Antenna handbook

Azimuth Pattern: Antenna radiation pattern viewed from above.

Vertical ¼ wave vs. Horizontal Dipole

Vertical

Horizontal

Elevation Pattern: Angle of maximum radiation in relation to the ground. Lower the better for DX.

Vertical

Horizontal

Vertical ¼ wave vs. Horizontal Dipole

Height above ground of a Horizontal antenna to be effective

“Sky shooter” Comparable to vertical Lowers angle even more

Bad for DX More gain than vertical Creates multiple lobes

Would require rotator

Yagi style but vertical?

How to get gain out of my vertical?

The Moxon

Variation of the Yagi Compact than Yagi

Equivalent gain of a Yagi High front back ratio

The Moxon

http://www.moxonantennaproject.com/design.htm

Free simulation software

http://www.qsl.net/4nec2/

Free simulation software

Vertical MoxonSimulated results

Horizontal MoxonSimulated results

The Vertical Moxon

End Fed Matching Network

• Pick permeability• too low: too much wire• too high: more loss• Self resonate secondary winding

in band to prevent additional reactance (16T)

• Measure Z at antenna input (2K)• Calculate turns ratio:

• Calculate primary winding: 16/6.3 = 2.5 turns

• Short secondary, measure primary Z, note reactance.

• To cancel out the inductive reactance, put series capacitor with same reactance in series with the input of the primary.

The Vertical Moxon

Future plansHex Beam

Future plansHex Beam

Future plansHex Beam

Thank you very much

DE AA3JH