KB9VBR J Pole Antenna Sheet 440

User Manual: J 440

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The modern J-Pole is derived from an antenna

called the end-fed Zep. Itʼs similar in design to

the end-fed antennas of the 1930ʼs; most

notably the antennas used on the Zeppelin

dirigibles. Of course the Zeps used on dirigibles

where long wire HF antennas that trailed out

the rear of the cabin. The modern J-Pole

antenna is much shorter and optimized for VHF

and UHF communication.

The J-Pole antenna can be best described as a

½ wave section over a ¼ wave vertical with a ¼

wave matching stub. The 2 quarter wave

sections at the base of the antenna run parallel

to each other. The current in the one section will

be out of phase of the other, keeping that

section of the antenna from radiating. The

remaining half wave section will radiate

extremely well since there is no counteracting

field to keep it from radiating.

As a half wave antenna, the J-Pole doesnʼt

need any radials or a ground plane to work.

Average gain with a 2 meter J-Pole is about 3

db. Many like to compare the gain and antenna

pattern to that of a Ringo Ranger. The biggest

advantage of the J-Pole is that it is at DC

ground, so it can be mounted just about

anywhere and still work. No special grounding

or a groundplane is necessary for operation.

KB9VBR J-Pole antennas are built with the

highest quality materials and individually tested

for optimum performance. If you have any

questions about your antenna, or have a

special request, please let me know. I am more

than willing to help you out.

KB9VBR

J-Pole Antennas

Affordable antennas with

superior performance.

• Solid copper construction, Durable

in the harshest of environments

• SO-239 connector soldered on at

point of lowest SWR for band

• Low SWR. 1.2:1 or less at 146

MHz for the 2 meter J-Pole.

• Efficient radiator. 3db of gain when

compared to a 1/4 wave

groundplane antenna.

• 11 inch mounting stub for easy

installation. 6 meter model has 18

inch stub.

•Can be painted to blend into the

environment.

©2011 Michael Martens • All rights reserved

Order more J-Pole Antennas

The Original 2 meter J-Pole

Our most popular seller. This antenna has

outstanding performance on 2 meters and loads up

quite well on 70 centimeters. Overall length is 69

inches with an 11 inch mounting stub.

The Breakaway 2 meter J-Pole

The 2 meter J-Pole with a two piece design. Now the

antenna will fit in the trunk of your car. Carry it with

you for fast emergency communications deployment.

The 6 meter J-Pole

A monster of an antenna measuring in at 13.5 feet.

Excellent performance, hit repeaters 40 mile away

with only 5 watts. The 6 meter J features a two piece

design for shipping and easy storage.

The 222 MHz J-Pole

Its difficult to find quality antennas for the 222 MHz

band. This antenna will get you on the air with great

signal reports. Overall length is 49 inches with an 11

inch mounting stub.

The 440 MHz J-Pole

440 MHz single band dedicated antenna. Short,

lightweight, and always more gain than a 1/4 wave

groundplane; only 30 inches overall with 11 inch

mounting stub.

Other antennas (see website for details)

153 MHz Public Safety / MURS Antenna

155 MHz Marine band / Public Safety Antenna

162 MHz Railroad / NOAA Weather Antenna

462-467 MHz GMRS band Antenna

118-127 MHz Airband Antenna

87-108 MHz Low Power FM band Antenna

To Order, Contact:

Michael Martens, KB9VBR

1228 Arthur St

Wausau, WI 54403

(715)845-4218

kb9vbr@yahoo.com

Order online at: www.jpole-antenna.com

J-Pole antennas are balanced antennas. Since you

will be connecting a balanced antenna to an

unbalanced feedline, you may need to construct a

balun to decouple the coax from the antenna.

Doing so will increase the antennaʼs performance.

Making the balun is easy, just take 5 loops of coax

and loop them into a 6 inch diameter bundle.

Secure the bundle with cable ties. The balun

should be positioned about a foot away from the

feedpoint.

Mount the J-Pole on a mast with at least 2 hose

clamps or U-Bolts. The mounting section of this

antenna is 11 inches long, that should be plenty of

length to clamp the antenna onto a mast. The J-

Pole is at DC ground, that means you can clamp it

directly to a metal mast or support structure without

affecting its performance. Just make sure that the

mounting mast does not extend above the T

connector. Seal the PL-259 connector with high

quality electrical or Coax Seal.

As the antenna is exposed to the elements, the

bright copper finish will slowly oxidize and create a

lovely dark patina. This oxidation does not affect

the antennaʼs performance.

The copper J-Pole is extremely durable. I have one

installed at home that has gone through several

winters without any problems. These antennas can

also be mounted on a mast and jammed into the

ground for an emergency station. Local ARES

groups could work with emergency government to

place J-Poles on the roofs of fire stations and

shelter locations. These antennas require no

maintenance and are inexpensive enough that they

can be installed everywhere.

143 144 145 146 147 148 149

1.7

1.5

1.3

1.1

1.3

1.5

1.7

2 Meter J-Pole SWR Chart 144-148MHz

Go to www.jpole-antenna.com/FAQ for more

antenna questions and answers.

What are the all copper J-Pole antennas

constructed with?

My J-Pole antennas are constructed out of Type M

solid copper pipe for the ultimate in durability and

weather resistance. All joints are soldered with rosin

core solder. An SO-239 connector is soldered onto

the antenna at the point of lowest SWR.

How do your two meter J-Poles perform on the

440 MHz band?

The two meter J-Pole is tuned for maximum

efficiency at the 2 meter band where the SWR is

1.2:1 or less at 146 MHz. It is a pretty good

performer on the UHF band where the SWR is 1.5:1

– 2.0:1 between 445-450Mhz. This is still within the

range of what modern radios can handle.

Can the antenna be painted?

You may paint the antenna with nonmetallic paint to

protect it and help it blend into the surroundings. If

you want to keep the antenna looking shiny and new

on the tower, you can also paint it with a clear

lacquer or nonmetallic enamel paint.

How to I connect your antennas to my hand held

portable radio?

While the J-Pole antennas are designed to be base

station antennas, they will all work very well with your

HT or hand held radio. The antennas have an

So-239 connector on them, and I recommend using

coax cable with Pl-259 connectors to connect the

antenna to the radio. You will need an adaptor to

connect the standard coax with Pl-259 connectors to

your portable radio. Radio Shack does sell an BNC

to SO-239 adaptor and an SMA to SO-239 adaptor.

How much power will a J-Pole antenna handle

Typically, the 2 meter all copper J-Pole antenna will

handle 250 watts or more of power. Copper is a very

efficient conductor and will tolerate and dissipate

heat energy very well.

What type of coax should I use?

Coax size is dependent on a couple of factors,

most notably the length of your run and the

frequency of your antenna. VHF and UHF signals

are more prone to attenuation in the coax, so a low

loss cable should be selected.

Feedline loss in DB per 100 feet:

Cable

146 MHz

446 Mhz

RG-58

6.5

12.2

RG-8X

4.7

8.6

RG-8U

2.3

4.7

9913/LMR400

1.6

2.9

A loss of 3 db will cut your power in half. A six db

loss will cut your power into 1/4. I recommend

RG-8 if your cable run is over 50 feet and RG-8X if

it is less than 50 feet. You shouldnʼt use RG-58 for

VHF/UHF unless it is a very short run (less than 15

feet.). GMRS J-Pole users should only use RG-8

for short runs and Belden 9913 for longer runs.

The SWR is really high on my antenna. What

should I check?

Here are a few things you can check if your SWR

is high.

• Check the coax, make sure there are no

problems associated with it. The connectors

should be well soldered or crimped without any

shorts and there should be be any apparent

kinks in the cable.

• Check the mounting location, nearby buildings

will affect the SWR. Keep structures at least six

feet away from the antenna, or make sure the

antenna is above the structure.

• Make a balun to keep RF from coming back

down the coax. Make a coil of about 5 loops of

coax with a coil diameter of about 6 inches. This

coil should be located about a foot away from

the feedpoint of the antenna. Secure the coil

with cable ties or electrical tape.

• Inspect the antenna itself. Is the solder loose or

cracked at the feedpoint. If it is, let me know.