antenna presentation utah amateur radio club jed w. petrovich, ad7kg march 6, 2008

Antenna PresentationAntenna Presentation

Utah Amateur Radio ClubUtah Amateur Radio Club

Jed W. Petrovich, AD7KGJed W. Petrovich, AD7KG

March 6, 2008March 6, 2008

IntroductionIntroduction

Starting outStarting out

Homebrew vs. CommercialHomebrew vs. Commercial

VHF/UHFVHF/UHF

Going the distanceGoing the distance

HFHF

ProjectsProjects

Q & AQ & A

Most Important?

Your First RadioYour First Radio

Hey, is this really going to work?

First Experiences

Roll up J-PoleLadder Line J-PoleCopper CactusAluminum J-PoleGoing Mobile

There are Limitations!

HF Antennas

CompromisePerformanceWeight and SizeCostAvailable SpaceRestrictionsEtc.

Perhaps the #1 Consideration?

The 1/2 Wave DipoleThe 1/2 Wave Dipole

Length of dipole in feet Length of dipole in feet = =

468 468 f (MHz)f (MHz)

The 1/2 Wave DipoleThe 1/2 Wave Dipole

Radiation pattern for a dipole antennaRadiation pattern for a dipole antennalooking down from above the antennalooking down from above the antenna

The 1/4 Wave VerticalThe 1/4 Wave Vertical

Length of vertical in Length of vertical in feet = feet =

234 234 f (MHz)f (MHz)

The 1/4 Wave VerticalThe 1/4 Wave Vertical

A side view of the radiation pattern of a 1/4 waveA side view of the radiation pattern of a 1/4 wavevertical. From above the pattern is round like a vertical. From above the pattern is round like a doughnut. A perfect ground would be a car roof.doughnut. A perfect ground would be a car roof.

The YagiThe Yagi

The yagi is The yagi is perhapsperhaps the ham’s favorite the ham’s favorite directional antenna.directional antenna.

They usually consist of one driven They usually consist of one driven element, and several “parasitic” (un-element, and several “parasitic” (un-driven) elements.driven) elements.

Reflector (longer than driver)Reflector (longer than driver)

Driven Element (1/2 wave dipole)Driven Element (1/2 wave dipole)

One or more Directors (shorter than the One or more Directors (shorter than the driven element)driven element)

The YagiThe Yagi

A 3 element HF YagiA 3 element HF Yagi A VHF A VHF YagiYagi

The YagiThe Yagi

GainGain

BoomBoomFe

ed

line

Feed

line

Reflect

or

Reflect

or

Dir

ect

oD

irect

orr

Dri

ver

Dri

ver

The reflectorThe reflectoracts like a acts like a

mirrormirror

The directorThe directoracts like aacts like a

lenslens

The YagiThe Yagi

The yagi antennaThe yagi antennafocuses RF energy infocuses RF energy inone direction, givingone direction, givingthe appearance ofthe appearance ofgetting “free power.”getting “free power.”

This free power isThis free power iscalled Antenna Gain.called Antenna Gain.

HexBeam

HexBeam Design

Classic Broadband

Size Comparison

Sound Check

Iceland/UK 20 Meters – HexBeam

USA/UK 20 Meters – HexBeam

USA/UK 20 Meters – Doublet vs. HexBeam

Portable Operations

Safety Matters!

Antenna SafetyAntenna SafetyDon’t put antennas. where they Don’t put antennas. where they could fall across power linescould fall across power linesDon’t climb towers without a Don’t climb towers without a safety belt.safety belt.Don’t do tower work without a Don’t do tower work without a ground crew.ground crew.If you’re working under the tower, If you’re working under the tower, wear a hard hat.wear a hard hat.

LightningLightningGround antennas when not in use.Ground antennas when not in use.Ground the tower structure itself.Ground the tower structure itself.Ground rods should be copper or Ground rods should be copper or copper clad steel and 8 ft. long.copper clad steel and 8 ft. long.Disconnect AC power mains during Disconnect AC power mains during storms, or use line conditioners or storms, or use line conditioners or surge suppressors.surge suppressors.GET OFF THE AIR DURING SEVERE GET OFF THE AIR DURING SEVERE STORMS!!STORMS!!

Radio Frequency Safety

RF EnergyHigh Voltages

SWR – Protect Your RigSWR – Protect Your Rig

SWR (standing wave ratio) is a SWR (standing wave ratio) is a mathematical expression of the power mathematical expression of the power going to an antenna and the power going to an antenna and the power being reflected back.being reflected back.

The idea is to get as close to 1:1 as The idea is to get as close to 1:1 as possible.possible.

Most hams are happy with SWR of 1.5:1.Most hams are happy with SWR of 1.5:1.

The best way to get a good SWR is to The best way to get a good SWR is to cut the antenna to resonance.cut the antenna to resonance.

Feed linesFeed lines

Feed line connects your radio to the Feed line connects your radio to the antenna.antenna.

Feed lines are either balanced (neither Feed lines are either balanced (neither side grounded) like ladder-line or side grounded) like ladder-line or unbalanced (one side grounded) like unbalanced (one side grounded) like coaxial cable.coaxial cable.

Either type can be used in your station.Either type can be used in your station.

Coax is more popular and easier to work Coax is more popular and easier to work with.with.

CoaxCoax vs.vs. Ladder LineLadder Line

Can be buried or Can be buried or run near metal run near metal objects.objects.

Less RFI since Less RFI since outer shield is outer shield is usually grounded.usually grounded.

WeatherproofWeatherproof

Easy to handle Easy to handle and connectand connect

Very low signal Very low signal lossloss

Can tolerate high Can tolerate high SWRSWR

Can tolerate high Can tolerate high currentcurrent

Why join the ARRL?Why join the ARRL?Since 1914 the American Radio Since 1914 the American Radio Relay League has represented Relay League has represented the interests of Radio Amateurs the interests of Radio Amateurs before the FCC and Congress. before the FCC and Congress. While there is room for policy While there is room for policy debate, those who do not support debate, those who do not support the ARRL have virtually no voice the ARRL have virtually no voice in matters concerning ham radio. in matters concerning ham radio. Also, the QST magazine is an Also, the QST magazine is an excellent educational tool, full of excellent educational tool, full of interesting articles and fun interesting articles and fun projects.projects.

Resources

AD7KG@arrl.nethttp://www.ad7kg.com

http://www.cebik.com/Hexbeam

http://www.leoshoemaker.com/hexbeambyk4kio/general.htmlhttp://karinya.net/g3txq/hexbeam/

ARRLOther Hams (Elmers)

In Summary…

ProjectsQuestions?Comments?