Public service through Amateur Radio

Don Kovalchik, W8DPK

51 ohm impedance. (Remember that the im-

pedance of a coaxial cable is determined by the

ratio of the conductor sizes and the dielectric

material.). Without getting into the compli-

cated mathematics, it was determined that dif-

ferent values of impedance are optimum for

different parameters. At any given size, cables

with the highest power capability were about

30 ohms. A value of 60 ohms is ideal for the

highest voltage breakdown. The optimum

value for the least attenuation is about 77

ohms. A 50 ohm cable is a reasonable com-

promise of all these parameters.

In the 1950’s, flexible coaxial cable with solid

polyethylene dielectric became popular and

affordable. The impedance of a 77 ohm air

dielectric cable is reduced to about 50 ohms

when polyethylene is used for the dielectric.

So, 50 ohms became the de-facto standard for

coaxial cables used for radio communications.

It turns out that a 50 ohm transmission line is

also a reasonable match to the basic antenna

types. A resonant dipole is about 72 ohms, and

a resonant ¼ wave vertical is about 35 ohms,

both of which cause an acceptable 1.4:1 SWR

to occur on a 50 ohm cable. Complicated im-

pedance matching networks are not needed.

Now you know why 50 ohms is so special.

73,

--Don-- W8DPK

Is 50 Ohms Special?

Did you ever wonder why practically all

modern amateur radios are designed to use a

50 ohm impedance antenna system? Why

not 30, 75, 100, 300, or some other arbitrary

value? Is something special about 50 ohms?

Before World War II, coaxial cable was

mostly unheard of and hams connected

open-wire feedlines of unknown impedance

to their transmitters. The transmitters had a

very wide range of adjustment and could

match just about anything that was con-

nected.

With the advent of radar transmitters in

WW-II, coaxial cable transmission lines

with low loss and high power capability

were designed. Early coaxial cables used

rigid tubing, often using standard sizes of

copper pipe, such as 2” for the outer con-

ductor and ¾” for the inner conductor.

With an air dielectric, this yielded about a

April 2013

For those who enjoy working the

Special Event stations here are sev-

eral that are being held in Ohio:

Cambridge Glass

Apr 6, 1300Z-2100Z, W8VP, 14.260 7.235. Certificate & QSL

www.w8vp.org

Scoutfest 2013 Apr 19-Apr 21, 1700Z-1700Z, K2BSA/8, Zanesville, OH. Muskingum Valley Council

BSA. 14.290 7.190. QSL.

Hopalong Cassidy May 4, 1400Z-2200Z, W8VP, Cambridge, OH. Cambridge Amateur Radio Associa-

tion. 14.260 7.235. Certificate & QSL.

Soon after graduating from high school

Ruben joined the military where he was

trained to be a Wheel Vehicle Mechanic.

During his stint in the military he served at

Fort Knox, South Korea, and Petersburg,

VA., before being discharged back to civil-

ian life. Civilian life was good but it soon

became evident that the green back did not

go very far and a job would be required. At

a family gathering it was suggested that he

talk to Aunt Kathryn who worked at Ohio

Bell. This decision would unknowingly be

a turning point in his life and start him out

working for Ma-Bell. Ruben married in

1965, became the father of 2 who are both

graduates of Ohio State. Ruben changed

jobs three times during his working career

which led to more responsibility and pay

increase each time. Shortly after getting

married he bought a CB radio which led to

learning how to service radios. After CB

radio the interests turned to flying which

resulted in a Commercial pilots license with

an instrument rating, as well as becoming

an FAA flight instructor. In addition to the

FAA licenses Ruben also holds a First

Class Commercial Radio Telephone, and an

Extra Amateur Radio license from the FCC.

Who would have thought that one could go

from a toilet bowl cleaner to becoming a

Vice President , manager and staff engi-

neer. Ruben retired in July of 2005.

Apr 13 Cuyahoga Falls ARC Hamfest http://www.cfarc.org/hamfest2013.html

Apr 20 Jackson County ARC, Jackson , OH

Apr 28 Athens Hamfest, Athens, OH http://ac-ara.org/

May 17-19 DAYTON

Are you or someone you know

wanting to get your amateur

license or to upgrade? You

can take those exams which

are given by the Laurel Ama-

teur Radio VEC club. Make a

note of the dates and times be-

low:

July 4, 2013

September 5 2013

November 4, 2013

All exams will be given at the Madison

County Engineers office at State Route 42

and Interstate 70 where our club meetings

are held. All times will be 7 PM.

You can also check the ARRL web site

for locations in the area.

AMATEUR LICENSE EXAMS

Have extra gear sitting around that you

would like to sell or swap? The newsletter

can be a place to list your equipment with

your email address or phone number where

you can be reached. Send info to: editor@mcarcoh.org

FOR SALE OR TRADE--32 ft. aluminum

tower, Butterfly beam for 20,15, 12 and

10 meters. Make offer or will trade for

civilian tube equipment.

Dick, k8ugl1@juno.com.

Welcome to all the new hams who

passed their Amateur exams on March

7, 2013

Jeffery Clayton KD8UFA Tech

Michael Robison KD8UFB Tech

Robert Turri KD8UFC Gen

Hal Krohn Jr AC8NN Extra

William Hughes KD8UFD Tech

Francis Reed KD8UFE Tech

John Chancey KD8UFF Tech

On Tuesday March 19 NOAA weather

held a Skywarn training meeting at the

Madison County EMA building. The

meeting was well attended by the Amateur

Operators as well as persons from other

public service groups. Members who have

had the spotter training are encouraged to

monitor NOAA weather radio and radio

and TV as well as the NWS web site for

severe weather. When you know of ap-

proaching severe weather check into the

Skywarn net on 146.76 to report those

items that are of interest to the NWS.

Mr Jerry Pittenger, K8RA

presented a great program at

our March meeting on con-

struction techniques. He

brought along a number of

his projects which showed his

professionalism in building.

Jerry used a power point

presentation to show the

process from design to final

testing and documentation.

Jerry was first licensed in

1960 at the age of 12.

K8RA

On Saturday the 23rd members

took a field trip to see Jerry’s

shack and workshop. Jerry has a

very impressive shack which in-

cludes both up to date state of

the art gear as well as some very

nice vintage equipment. Jerry

says his hand crafted paddles

supplies the funds to equip the

ham shack.

The Madison County Amateur Ra-

dio Club meets on the second Wednesday

of each month. Meetings take place at the

Madison County Engineers Office at Inter-

state 70 and State Route 42. The entrance

is between McDonalds and Wendy’s on the

East side of 42. Meeting time is 7 PM

On the 4th Saturday of the month

they meet at the Der Dutchman Restaurant

for breakfast at 9 AM in Plain City.

Every Tuesday evening at 8 PM the

“Get together net” meets on the club re-

peater on 147.285 MHz. The net is open to

all and your are encouraged to join in and

learn to know other hams in the area.

MCARC Officers

President Don Kovalchik, W8DPK

Vice President Nick Pittner, K8NAP

Secretary Paul Yackey, KD8RMY

Treasurer Terri Kovalchik, N8TLK

Newsletter Jim Hartzler, K8EIJ

Plans are coming together for the Great

Lakes Division's Convention for

2013. The Voice of Aladdin Amateur Ra-

dio Club will host this year's event in con-

junction with their annual Columbus Ham-

fest in Columbus, OH on August 3. The

location is convenient and the facilities are

excellent.

We are pleased to announce that our Con-

vention Keynote Speaker will be ARRL

Chief Executive Officer Dave Sumner,

K1ZZ. Dave will bring a wealth of infor-

mation about what is happening in ham ra-

dio, both locally and on the international

scene. There will be two "tracks" of fo-

rums to include some favored ham radio

topics. Confirmed at this point are Carl

Leutzelschwab, K9LA speaking on Propa-

gation and Jay Adrick, K8CJY with a pres-

entation on the Mason, OH Voice of Amer-

ica Site and its history. More presentations

are in the works and will be announced as

they are confirmed.

Please save the date, and plan to be

there. As we get closer to the date, we'll be

able to provide the details for the conven-

tion luncheon, plus travel and lodging in-

formation.

This article from “Weavers Words” Jim

Weaver K8JE, Great Lakes Director

NOI ON RF EXPOSURE

On March 27, the FCC released a First

Report and Order, Further Notice of Pro-

posed Rulemaking and a Notice of Inquiry

(ET Docket Nos. 13-84 and 03-137). The documents seek to reassess the FCC’s RF

exposure limits and policies, as well as to

propose changes to the FCC’s rules regard-

ing human exposure to RF electromagnetic

fields. These proposed changes would af-

fect the Amateur Radio Service (Part 97) rules.

For more information on the NOI go to the

ARRL web site