Joe Horanzy AA3JH April 4th, 2013 K3DN Presentation Memoirs of DXCC I made a composite of all material I studied and learned from various sources to prevent paralysis of analysis. My background. Some of this is fundamental, but I build upon the data I was trying to find a good title to my presentation. Just antennas, no. It doesn’t give it justification. When I first started, I bought a G5RV and tossed it in the attic. The only thing I was able to do is to talk to a local few rag chewers on 80 meters and set off the house alarm. I was unable to talk to any one in Europe. So, I started studying the fundamentals. I had to weed out all the hype, snake oil marketing out there and piece data from many locations and compile the data until it all made sense. Joe Horanzy AA3JH April 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

Open to all license classes 10 meter progress Open 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 Main Object: Get on HF to communicate around the world (DX) with an antenna that is: Simple Low maintenance Ease of construction Readily available components Stealth Low cost But very efficient and effective.

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 Vertical They 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 Vertical Single Band How high: *235/ Freq (Mhz) example: for 14.1 Mhz 20 meter band 235 / 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 Vertical Ground 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 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. xmit Rr: Radiated resistance Rg: Ground resistance Tell how can you measure ground resistance….. From Arrl Antenna handbook

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.

COMPONENTS OR

Putting it all together Bungee cord 20M trap

Ground Connection

Ground Connection Close up

Multiband Vertical Resonate Traps:

Trap: Inductor/ HV Cap

Multiband Vertical Another approach Fan Vertical

Contacts made with home brew fan vertical antenna (40 to 10 meter) No amplifier.

Summary 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).

Gain Dbi : 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 - 2.15 Dipole in freespace can have 2.15 Dbi gain or 0 Dbd. From Arrl Antenna handbook

Vertical ¼ wave vs. Horizontal Dipole Azimuth Pattern: Antenna radiation pattern viewed from above.

Vertical ¼ wave vs. Horizontal Dipole Elevation Pattern: Angle of maximum radiation in relation to the ground. Lower the better for DX.

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

How to get gain out of my vertical? Yagi style but 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 Moxon Simulated results

Horizontal Moxon Simulated 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. Measure impedance Determine permeability of ferrite Turn ratio to get primary winding sqr (MI/Mo) Short sec, read primary Z to add cap in series.

The Vertical Moxon

Future plans Hex Beam

Future plans Hex Beam

Future plans Hex Beam

Thank you very much DE AA3JH