Ramsey Electronics Dipole Antenna DA-1 Guida utente

RAMSEY DA SERIES DIPOLE ANTENNA Page 1

Ramsey Electronics DA-1

•User tested, proven antenna technology to bring you the best

value.

•Clear, concise instructions are just what you won’t find with other

antennas. Our manual teaches you everything that you need to

know, and even points you in the right direction if you want to learn

more!

•Can be set up as a typical dipole antenna, or the popular “Inverted

V” configuration, for less space and excellent performance.

•Build a home brew antenna... right down to the last soldering

connection.

•These dipoles are virtually invisible, but do not compromise

performance, or signal capabilities.

•Perfect as a second antenna for those whose antennas won’t

handle a specific band.

•High quality components assure you a working antenna every

time... and tuning it is so easy!

•The right antenna at the right price.

Looking for an easy to build, solid performing antenna? The

dipole is hard to beat! These inexpensive, high quality

antennas are the time tested solution to price, relative

invisibility, and most of all, performance.

Page 2 RAMSEY DA SERIES DIPOLE ANTENNA

PARTIAL LIST OF AVAILABLE KITS

RAMSEY TRANSMITTER KITS

• FM-10 FM Stereo Transmitter

• FM-1,2,4 FM Wireless Microphones

• PB-1 Telephone Transmitter

• AM-1 AM Transmitter

RAMSEY RECEIVER KITS

• FR-1 FM Broadcast Receiver

• AR-1 Aircraft Band Receiver

• SR-1 Shortwave Receiver

• AA-7 Active Antenna

• SC-1 Shortwave Converter

RAMSEY HOBBY KITS

• SG-7 Personal Speed Radar

• SS-7 Speech Scrambler

• MM-5 Digital Music Maker Machine

• SP-1 Speakerphone

• MD-3 Microwave Motion Detector

• PH-10 Peak hold Meter

• LC-1 Inductance-Capacitance Meter

RAMSEY AMATEUR RADIO KITS

• FX Series VHF and UHF Transceivers

• HR Series HF All Mode Receivers

• QRP Series HF CW Transmitters

• CW-7 CW Keyer

• PA Series VHF and UHF Power Amplifiers

• Packet Computer Interfaces

• QRP Power Amplifiers

RAMSEY MINI-KITS

Many other kits are available for hobby, school, scouts and just plain FUN. New

kits are always under development. Write or call for our free Ramsey catalog.

DP-1 DIPOLE ANTENNA INSTRUCTION MANUAL

Ramsey Electronics publication No. MDA-1 Revision 1.0

First printing: August, 1994

written permission of Ramsey Electronics, Inc. Printed in the United States of America.

RAMSEY DA SERIES DIPOLE ANTENNA Page 3

DIPOLE

ANTENNA KIT

Ramsey Publication No. DA

Manual Price Only: $5.00

TABLE OF CONTENTS

Introduction ......................................................... 4

Antenna Description............................................ 4

How Does a Dipole Antenna Work? ................... 6

Schematic Diagram............................................. 7

Parts List............................................................. 8

What Kind Of An Antenna Is Best For You?....... 9

Construction Notes ............................................. 10

Antenna Construction ......................................... 13

Tuning Your Antenna.......................................... 15

Other Reading..................................................... 15

ASSEMBLY

AND INSTRUCTION MANUAL FOR

RAMSEY ELECTRONICS, INC.

793 Canning Parkway

Victor, New York 14564

Phone (716) 924-4560

Fax (716) 924-4555

Page 4 RAMSEY DA SERIES DIPOLE ANTENNA

INTRODUCTION

Welcome to your new dipole antenna. Dipole antennas are an extremely

popular form of antenna today, because they satisfy the demands of almost

any application! There are not many antenna designs that are so low cost,

simple and “invisible”. You may not know that they are also exceptionally

good radiators, beating many other antennas hands down. Their exceptional

qualities on low frequency bands such as 160, 80 and 40 meters is also a

great advantage over antennas many times their price.

As you may know, living in a neighborhood with other people may

immediately lead to problems with neighbors who are worried about the

effect that your antenna will have on them. Many people are worried about

your ham gear interfering with their television sets or radios. In addition,

many people who simply don’t know enough about your hobby may think

that it could attract lightning to their houses, or even fall off of your roof

(heaven forbid!) This is where the “invisible” properties of a dipole are so

important. In a short day’s work, you can install your antenna that to even

the nosiest neighbor might be strained to see.

But the great thing is that your antenna is also a great radiator. Is it any

wonder why hams who spend over a thousand dollars on beam antennas for

20, 15 and 10 meters also own dipoles to work the 160, 80 and 40 meter

bands? In fact, dipoles are one of the oldest, and most tested antennas in

existence. This is why we are proud to offer you a reliable, time tested

antenna design at low cost.

ANTENNA DESCRIPTION

Your Ramsey antenna has been designed for practicality, performance and

price. Every effort has been made to offer you not only high quality parts,

but also an affordable price that will make beginners starting in the hobby, or

avid hams looking for a second antenna feel good. Because we offer a

range of antennas, each designed for a different band, you will notice that

this book encompasses each of them. In the tables provided, use the data

that best resembles your particular purpose and needs.

RAMSEY DA SERIES DIPOLE ANTENNA Page 5

HOW DOES A DIPOLE ANTENNA WORK?

A dipole antenna is a long wire that is suspended between two points. The

wire is cut to a specific length, and is fed in the middle with a radio frequency

(RF) signal. One half of the antenna is hooked to the ground wire of the

transmission line, and the other is hooked to the center conductor.

As an RF signal is applied to a piece of wire, both an electric and a

magnetic field is set up around the wire. These waves propagate through

the air (or ether!) without limit. As these magnetic and electric fields reach

another station’s antenna (or about any other metal object in it’s path) the

exact reverse effect takes place on our antenna that our RF signal did. The

rapidly changing fields produce an RF current that your receiver can detect.

Although it is impossible to actually see the waves coming off of a dipole,

we can try to visualize it to understand it better. Take a piece of paper and

push a pen or pencil through the center. Hold it up in front of you. Let’s

pretend that the pencil represents our antenna, and the paper represents

where our signal is concentrated. As you can see, most of the radiation is

given off at a 90 degree angle to the antenna, with very little radiation

occurring parallel to the pencil. It is this property that makes the dipole

directional. Another advantage is that the radiation is at all angles around

the wire, and the signal has a maximum chance to skip through the

atmosphere, making the dipole ideal for DX.

An inverted dipole does have a number of advantages over typical dipoles.

For one thing, they take up less space, with some of their wire being used up

to climb a vertical distance, and a five percent reduction in antenna length

over a normal dipole. They also match their impedance more easily to a 50

ohm coaxial cable than a typical dipole, which has an impedance of 65

ohms. The inverted dipole also has a higher angle of radiation — making it

better for sky wave DX.

If you have any questions, we suggest that you look for the ARRL Handbook,

which has all sorts of great information for hanging antennas.

Page 6 RAMSEY DA SERIES DIPOLE ANTENNA

PARTS LIST

3 End Insulators

Length of Coaxial Feedline Cable

Length of Rope

1 PL-259 Connector

1 UG-175/U Reducer

Length of Antenna Wire

2 Wire Cable Ties

REQUIRED, NOT SUPPLIED

Some Good Friends (Suckers)

Soldering Iron Gun with Rosin Core Solder

Waterproof Sealant (Silicone) and Electrical Tape

Radio Transmitter

Sharp Knife

Wire Cutters

WHAT KIND OF ANTENNA IS BEST FOR YOU?

Unlike many antennas that you can find on the market, the Ramsey dipole

antenna is capable on being constructed in two configurations. These are, a

normal dipole, and an “Inverted V” antenna. A normal dipole is just what we

have been talking about. An Inverted V is a variation of a normal dipole that

features slanting wires for easier mounting on small properties, or where you

wish to mount the center of your antenna high without having to build two

high endpoints (see diagram on next page). Antenna critics agree that there

is little difference in performance between the two antennas.

One difference between the two types of antennas is the wire length.

Because of slightly different antenna characteristics, the Inverted V antenna

is slightly shorter. This has to do with a number of physical factors such as

end effect (the magnetic and electric fields at the end of the wire), and the

proximity and angle to the ground. To accommodate this difference in

RAMSEY DA SERIES DIPOLE ANTENNA Page 7

Page 8 RAMSEY DA SERIES DIPOLE ANTENNA

length, we have included a bit more wire than you should need to build either

antenna. This allows you to decide which antenna will serve you better.

CONSTRUCTION NOTES

Just a few notes before you begin constructing your antenna.

•Be careful when constructing your antenna! Throwing rocks through

windows, falling from trees, shooting a buddy during the famous bow

and arrow trick and becoming electrocuted are just a few of the hazards

that can ruin your day.

•If the weather looks threatening, wait for it to pass. The last thing that

you want is to be caught on your roof during a storm.

•Don’t take chances with your antenna. Secure it as well as you can, and

make sure that nobody will be able to touch it once it is mounted.

Transmitting while someone is touching it can be a shocking experience.

•When in doubt, have your buddies help you out! A few friends can make

the day a lot more enjoyable and easier... especially if they know a thing

or two about stringing antennas (or own a bow or arrow).

ANTENNA CONSTRUCTION

Now it’s time to begin construction! First, make sure that you have all of

your antenna parts, and they are easily accessible. You’ll also need tools

such as; ladders, electrical tape, waterproof sealant, a knife, wire cutters,

etc.

The first thing to do is to cut the antenna wire to the correct length. The

wire supplied with your kit has been cut somewhat longer than required, but

there is not enough for two antennas, so be careful when you measure! The

following table shows you the proper lengths to cut your antenna wires in

order to tune it to the proper frequency.

Please understand that the calculations that we have made are for a

frequency in the center of the band. If you prefer to use another frequency,

or a band that is not listed, simply find the lengths by using the following

equations. (It doesn’t hurt to add a foot or so to the calculated length to allow

for easier antenna tuning - it’s easier to simply “clip” off a bit of wire at a time

than it is to add wire.)

Total length of a dipole = 468/ frequency (in MHz) (in feet)

RAMSEY DA SERIES DIPOLE ANTENNA Page 9

Total length or an Inverted V = 445/ frequency (in MHz) (in feet)

Your Frequency_________ Calculated Length___________

ANTENNA

BAND

FREQUENCY

(KHz)

NORMAL

DIPOLE

INVERTED

ALL BAND >1850 129’3” 122’9”

160m 1850 129’3” 122’9”

80m 3750 63’9” 60’6”

40m 7050 33’11” 31’6”

20m 14250 16’9” 15’8”

10m 28500 8’5” 7’11”

Antenna Wire Length (per side)

NOTE: Measurements indicated for each side of dipole.

Page 10 RAMSEY DA SERIES DIPOLE ANTENNA

For example, to make a dipole antenna on 14.050 MHz, divide 468 by

14.05. The total dipole length be 33.31 feet or approximately 33 ‘4”. Don’t

forget that you need to insert a feedline in the center, so it must be cut into

two pieces that are one half the length (16 feet, eight inches).

Wire Length (approximate length packed with indicated antenna kit)

160m or ALL BAND .................. 262’

80m ............................................ 132’

40m ............................................. 72’

20m ............................................. 38’

10m ............................................. 21’

Indice

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