Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 1 How to Build a Dual-Band Antenna for 2M/70cm.

Slides:



Advertisements
Similar presentations
P. M. Livingston (Presentation from a few years back) An 80 meter Aerostat-borne Phased Array for Field-Day.
Advertisements

Amateur Radio Technician Class Element 2 Course Presentation
Jeopardy Q 1 Q 6 Q 11 Q 16 Q 21 Q 2 Q 7 Q 12 Q 17 Q 22 Q 3 Q 8 Q 13
Pneumatic Cylinders Chapter 3.
Addition Facts
Sectional Assembly and Installation
Antenna Presentation Utah Amateur Radio Club Jed W. Petrovich, AD7KG March 6, 2008.
Coaxial Connectors, Coaxial Cable, Feed Line, and a Simple Antenna.
AMATEUR RADIO TRAINING Feeders & Antennas v1.101 © essexham.co.uk.
Antenna Fundamentals Lecture 4.
Addition 1’s to 20.
25 seconds left…...
Feeders and Antennas.
Intermediate Course (5) Antennas and Feeders Karl Davies East Kent Radio Society EKRS 1.
5 Foundation Course Feeders & Antennas EKRS KARL DAVIES 1.
Let’s Design An Antenna VK3PY
1 Chelmsford Amateur Radio Society Foundation Licence Course Murray Niman G6JYB Slide Set 5: v1.2, 16-Dec-2007 (5) Feeders & Antennas Chelmsford Amateur.
Chapter 13 Transmission Lines
Introduction to Antennas Dipoles Verticals Large Loops Yagi-Uda Arrays
Constructing VHF / UHF Antennas. Presented at Ham Com 2014 Larry Brown WB5CXC Charles Webb W5WF.
APRS ANTENNAS by ED LAWRENCE WA5SWD SIMPLIFIED & TRANSMISSION LINES.
Part I: Dipoles by Marc C. Tarplee Ph.D. N4UFP
1 Chelmsford Amateur Radio Society Advanced Licence Course Murray Niman G6JYB Slide Set 13: v1.1, 10-Nov-2005 (5) Feeders Chelmsford Amateur Radio Society.
Foundation Licence Feeders and Antennas. What they do Feeder: transfers RF current between a transceiver and antenna without radiating radio waves. (Hope.
SLIM JIM ANTENNA discussion
Antenna Types WB5CXC.
Antennas.
Antennas Demystified Scott Honaker N7WLO. Importance of Antennas Antennas are as important as the radio Antennas are as important as the radio A $5000.
Chapter 19: Antennas By: James VE3BUX. Definition The Modern Dictionary of Electronics defines an antenna as: That portion, usually wires or rods, of.
Chapter 6 Antennas Antenna Basics
Antenna Experiments & Explanations FCARC November 17, 2014 Al Woodhull N1AW.
ESTeem Training Class Antenna Fundamentals. Decibels (dB) Used for all mathematical calculations in the radio world. – dB is a logarithmic number dB =10.
Checking Antenna Systems
Joe Horanzy AA3JH April 4th, 2013 K3DN Presentation
Two Bands from One Dipole Marc C. Tarplee Ph.D., N4UFP ARRL South Carolina Section Technical Coordinator.
End Fed Antennas End Fed Long Wires
Antenna Types Dipole Folded Dipole Monopole
General Licensing Class
GAMMA MATCHES Ozaukee Radio club November 2013 A quick overview of the steps needed to adjust an antenna matching network usually seen on many older single.
General Licensing Class G9A – G9D Antennas Your organization and dates here.
L BAND HELIX ANTENNA ARRAY
Simple radio communications system. Electric field around elements.
Basic Wire Antennas Part I: Dipoles. Dipole Fundamentals A dipole is antenna composed of a single radiating element split into two sections, not necessarily.
SUBELEMENT G9 ANTENNAS AND FEEDLINES [4 Exam Questions–4 Groups]
G9 - Antennas 1 G9 – Antennas and Feedlines [4 exam questions - 4 groups] G9A - Antenna feed lines: characteristic impedance and attenuation; SWR calculation,
Technician License Course Chapter 4 Lesson Plan Module 9 – Antenna Fundamentals, Feed Lines & SWR.
Part I: Dipoles by Marc C. Tarplee Ph.D. N4UFP
RF Propagation No. 1  Seattle Pacific University Basic RF Transmission Concepts.
Moxon Beams Design & Building by WB5CXC 2006 Ham - Com.
Antenna Basics.
Basic Wire Antennas Part I: Dipoles.
Part I: Dipoles by Marc C. Tarplee Ph.D. N4UFP
AMATEUR RADIO TRAINING
AMATEUR RADIO TRAINING
A TECHNICAL BRIEFING FOR AMATEUR RADIO OPERATORS
Antennas 10/18/2017.
Technician Licensing Class
“So . . how does this J-Pole thingamabob work?”
Building and installing
ARRL – Illinois Section March 6, 2008
Technician Licensing Class
20M Antenna.
Ham ANTENNAS: A practical introduction to The THEORY AND operation
Part I: Dipoles by Marc C. Tarplee Ph.D. N4UFP
What is a beam antenna? A. An antenna built from aluminum I-beams
A “build to spec” approach
End Fed Half Wave Antennas
Emergency Communications Portable J-Pole Construction
WELCOME.
Presentation transcript:

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 1 How to Build a Dual-Band Antenna for 2M/70cm

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 2 Rubber Ducks are Kinda Like Rubber Chickens Rubber duck nearly an isotropic source, but not as good –Victim’s head absorbs some of the RF (maybe that explains a few things…) –Capacitance to body makes a “sortaground” that supplies half of the antenna plus a decent dummy load. –Directionality based on loss, not gain Alternatives commonly used –5/8 antenna on cookie sheet –¼ wave antenna on cookie sheet

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 3 Dipole as a 2-m antenna Limitations Current distribution Voltage distribution Power distribution Ground plane as a squished dipole

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 4 A Lecherous Episode Transmission line theory Standing waves With low SWR voltage and current do not change much as you move along the line With high SWR voltage and current form nodes and loops along the line Old-time Zepp antenna was voltage fed Source of RF Short or Open A V Lecher Wires (Open-Wire Transmission Line)

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 5 Stubs An open or shorted quarter-wave stub inverts the impedance at the input end. –If the far end is shorted, there is a very high impedance looking into the stub –If the far end is open, there is a short looking into the stub. –If you start at the shorted end and move toward the input, you will notice that the impedance is zero at first (high current, very low voltage). As you move away from the short, you’ll see the impedance rise (less current, more voltage) until you reach a voltage max at the input to the stub. –This gradual change in impedance can be used to match a feedline to the stub. The higher the impedance of the feedline, the farther from the short the feedpoint must be.

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 6 Stubs Again A half-wave stub acts like two quarter- wave stubs. –If you put 2 quarter wave stubs together, you invert the impedance twice! –Since the impedance is inverted twice, looking into a half wave stub you see exactly the same impedance that exists at the far end. But a three-quarter wave stub acts precisely a quarter-wave stub (in a lossless line)

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 7 Impedances along J-Pole Matching Stub (This part does the work of radiating) (This part does the work of matching the line to the dipole so that it can do its work.) Voltage-fed dipole ¼ wave stub Operation of the J- pole depends on two different functions: matching and radiation Radiation gets all the credit, but will not happen without proper matching. “Thunder is good, thunder is impressive, but it is lightning that does the work.” - Mark Twain

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 8 Dimensions of the Finished Antenna 55¼” 6” 18⅝”

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 9 J-pole construction –Required Materials ½” EMT conduit, 10’ section (Home Despot $2.89) 3/8-24 x 36” all-thread rod (Elliot’s $2.59) 3/8-24 locking nuts, 3 each (Elliot’s $0.20 each) Number 12 hose clamps, 3 each (Elliot’s $0.59 ea) 5” Stanley L-bracket (Despot $2.59) UHF to 3/8” antenna mount (Texas Towers $4.89) –Optional Materials ¾” EMT conduit, 6” or 8” hose clamps, qty 3,

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 10 Required Tools –Electric drill or drill press – 1/2” Metal-cutting bit – 3/8” Metal-cutting bit Vise Hacksaw Screwdriver SWR meter good at 146/450 MHz Dual-PL259 coax patch cable Feedline to your shack with PL-259 at antenna end

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 11 Drill the Bracket Drill ⅜” Drill ½” WARNING! Metal shavings may fly into eyes, causing loss of vision. Wear eye protection while drilling bracket. Rapidly rotating bracket may cause serious hand injury. Do not let this bracket get loose while you are drilling. Use clamps or drill vise to keep it securely held in place. 5-Inch STANLEY L-Bracket

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 12 Cutting the All-Thread –“Measure twice, mark well, saw once…” –Measure from original ends only because threads on ends are normally good. –After measuring and before sawing, put 2 nuts on 7½ “ end, one nut on 18½” end. –Clamp the junk-box section in vise to saw rod. 18½”7½”About 10” 144 MHz ¼ wave, 440 MHz ¾ wave 440 MHz ¼ Wave Doesn’t matter! Put in Your Junk Box

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 13 Steps to Success 1.Drill the bracket. 2.Measure and Saw the all-thread. 3.Mount antenna mount on bracket. 4.Mount bracket to conduit. 5.Install 18-inch all-thread. 6.Use SWR meter to adjust all-thread and position of bracket on conduit for lowest SWR at MHz. 7.Install 6-inch all-thread and hand-tighten nuts. 8.Adjust 6-inch all-thread for lowest SWR on 446 MHz. 9.Then alternately adjust length of 18-inch all-thread and 6-inch for best SWR on Finally, adjust position of bracket on conduit for best 2M SWR. 11.Tighten and check all hardware 12.Weatherproof entire area above and between conduit and bracket with caulking compound or silicone sealer. 13.Ground with #12 or larger copper wire for lightning protection

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 14 Current Distribution in the J-Pole Maximum current is Over 3’ from base! Current is Good! It’s current that causes radiation, so the higher the current max, the better. Thanks, W4RNL

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 15 If some is good, is more better? The standard J-pole extends ½ wave above the top of the matching stub, with maximum current in the middle of the ½ wave element. Of all simple vertical antennas over ground, the 5/8 wave radiator has the lowest angle of radiation, however the base of the 5/8 antenna presents a relatively low impedance, not the high impedance offered by the ¼ wave stub. This suggestion is a flop. The full-wave antenna is voltage fed, so it readily takes all the available power from the stub, however the phasing of the currents in the two half-waves actually moves the angle of maximum radiation UP and away from the horizon where we need it. The 1 ¼ wave antenna has two strikes against it. First, it is an odd multiple of a quarter-wave radiator, so presents a low impedance at the bottom. It wants low voltage, high current – just the opposite of what the stub offers. Also it has the same sort of phasing problems as the full-wave radiator. Right Wrong

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 16 An Even Better J-Pole - Electrically The gain is about 7.4 dBi. This value is about dB higher than the average gain of a single-radiator J-pole. Indeed, although many folks like to bandy the gain advantage of a collinear arrangement as 3 dB greater than a single section, we rarely obtain in real antennas more than about a dB increase in gain. Compared to many vertical antennas, the collinear J-pole shows a remarkable reduction in high-angle radiation. For any vertical collinear array, the only place from which to obtain energy for increased gain at lower elevation angles is from the high-angle energy of a single section. Thanks, W4RNL

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 17 Crankin’ up the Gain with a Jagi Thanks, W4RNL

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 18 Your Assignment 1.Use your J-Pole courteously! 2. Go to W4RNL’s website, and browse the best antenna site on the Web. There’s also great information on the history of ham radio and even some ham tales! “…every face in the room visibly blanched at the sight of the dreaded Wouff Hong, that ancient instrument of torture used to enforce the rules of good operating and the Amateur’s Code…”

Don Murray W9VEBuilding a Dual-Band Antenna Mentorfest 10/23/04 19 Just for Fun Make a jackleg antenna range to see how your favorite ducky or other portable antenna stacks up to your J-pole. Indicator Calibrated Step Attenuator Remote Antenna Under Test Standard Talkie in Standard Position