What's all this Coax stuff anyway? What
type of Coax do I use? What do the Coax type numbers tell me?
Why 50 Ohm coax? Most of us use coax every day, We bought the
antenna with coax attached or the radio instruction book said
to use it. But why coax and not open line feeder cable in the
300 to 600 ohm range like they used to use? For that matter what's
wrong with a wire right from the back of the radio. A wire from
the back of the radio presents some special problems. First the
wire from the radio becomes part of the antenna and radiates as
well as the antenna. This causes interference as well as affecting
the antenna pattern. Second, a high voltage point appears in the
antenna wire at, or near the connector. This is a serious fire
hazard when you consider that most of us have to pass that wire
through a wall of some kind and the wall is usually have wood
or some other combustible in them. Open line feeders solved some
of these problems by balancing the currents between the feeder
legs. The radiation field also tended to stay contained between
the legs of the feeder line until the wire was split into antenna
elements or legs. This minimized the interference or strong radiation
fields in the shack. Tube amplifiers were also high output impedance
devices, on the order of 2000 ohms. (Plate Load = Plate voltage
(Typ. 1000v)/Plate current (Typ. 500ma)) so matching a tube amp
with an output impedance of 2000 ohms to a 600 feed line only
required 3.3 to 1 transformer. This still leaves us with the problem
of high voltage on the antenna line. Assume a power of 1000 watts,
an impedance of 600 ohms and remember the formula for Voltage
of E = square root (PxR). This leaves you a voltage of 774.596
volts. If the line Impedance is changed to 50 ohms this reduces
the voltage on the antenna line to 223.6 Volts.
Coax came about to eliminate some of the high voltage problems and radiation problems. Coax by design is self-shielding since the outside jacket is at ground potential. Because the inside conductor is insulated and shielded, hazardous voltage levels don't appear on the coax except at the antenna connection itself.
Why 50 ohm Coax?
This is best answered in two parts, First, coax isn't all 50 ohm, it ranges in impedance value from 30 to 90 ohms. Second the lowest possible transmission loss occurs at about 70 to 80 ohms while the highest power handling occurs at about 30 ohms. Because of these factors a compromise between line loss and power transfer was struck at 50 ohms. This explains however why Cable TV firms who have huge distribution networks still use 75 -ohm coax.
Coax is available to us by different
Type Numbers. Most of us are familiar with 50-ohm cable types
RG-58, RG-174, RG-213, RG-214, and 9913 and the 75-ohm cable types
RG-59 and 783. Cable with a "RG" in the type number
means "Registered" and all this really means is someone
filled out the forms to register it, by itself this means nothing.
Cables that are Mil Spec. qualified for lot certification (Per
MIL-C-17D) will be listed as RG-XX/U. The numbers between the
letters were assigned in numerical order, from 1. This can be
used to indicate only the products registration. For example an
RG-8 coax was registered before the RG-213 coax.
Coax that is marked "RG-8 TYPE" means that these cables are similar in impedance, size, power handling etc. to the Mil Spec. qualified cables, but have never gone through the actual certification. For our application these will work fine.
What Coax to Buy?
If you have looked at these coax types, they come in several diameters. Generally if you are going to be handling high power (200 plus Watts) or your coax runs are going to be very long (Over 100 feet) you need to be using one of the larger coax such a RG-8, or RG-213. If you are working the satellites and low line loss is a major concern, a coax such a 9913 or RG-214 should be used. The RG-214 coax is a double shielded RG-213 type coax and usually is a lot of trouble to find connectors for, and to work with. For general use such as short runs for the car, a few jumpers for the shack or a length of coax for emergency use, RG-58 coax is a good choice. RG-58 is the least expensive of the coax types and serves very well for low to medium power applications in the HF to UHF regions.
Coax can be found on the surplus market. But again caution should be the watchword. Much of the coax found on the surplus market are leftovers from the Cable TV industry. Avoid any coax with a Teflon dielectric. These were made for High Temperature/Hostile environment applications and usually have inferior signal handling characteristics compared to standard coax. Hard-line/Heliax type coax can be found in 50 ohm impedance, and there are coax connectors available for this type of coax. About the only application that justifies this type of coax is a repeater installation. Its expensive, hard to bend, hard to connectorize, hard to secure to a tower and its just plain heavy. Any of the 50 ohm coax will work for our application. Choosing the best coax for you application will enhance your station operation. Using the best coax for your application can make the difference between being heard and being QRM.
Copyright 1996 Gerald Crenshaw WD4BIS. All rights
This appeared in the March/April
1998 issue of "YL Harmonics'', the newsletter of' the Young
Ladies' Radio League, Margaret Dunn-KC7L.XS Editor.
When we look back on the history of
amateur radio, certain names come up immediately: Hiram P. Maxim
and Clarence Tuska, the founders of the ARRL; "America's
Number 1 Ham", Irving Vermitya (and many CQ and QST readers
undoubtedly made contact with W1ZE during his long and illustrious
career); the great inventor Edwin Howard Armstrong; and of course,
Guglielmo Marconi himself. But there were some other pioneers
who have seldom gotten the credit they deserve-- a small number
of women who entered the game at a time when few in society thought
they were capable. These women learnt Morse code, built (and sometimes
won awards for) their own receivers, and surprised many people
who believed radio was a man's hobby. And while most were not
inventors, their presence in the family of amateur radio made
a positive impact, and inspired other women to follow in their
Unfortunately, telling their stories
has sometimes been a challenge, as Louisa B. Sando (W5RZJ) found
out when she began researching her excellent book "CQ-YL".
Although women amateurs absolutely did exist even in the earliest
days, they frequently operated stations run by their father or
brother or husband, and did not have call letters in their own
name. In QST April 1923 issue, for example, it mentioned that
Lillian Hume was an amateur who worked from her brother's station,
9DTI; however, that station was only listed in his name-- George
Hume. Further, some women who did have a station in their name
subsequently got married and moved to a new city, leaving no information
about what their new name was. (And while I am sure most men were
very understanding about their wife's hobby, several of the women
I interviewed about those 'good old days' told me that when they
married, their husband discouraged them from continuing on with
ham radio-- supposedly this was not a properly feminine activity
for a wife and mother... How times have changed!!!)
Like Ms. Sando, I too encountered the
problem of not finding the names of women amateurs: I noticed
in my research that some of the younger women who grew up in the
late teens and early 1920s made use of school stations-- but the
call books of that time did not list the members of school or
club stations by name. So, unless a young woman was written about
somewhere else, there was no way for me to find out who she was,
or how many clubs had women participants. I might never have known
that 8ME, a high school station in Beaver, PA, was where a certain
15 year old named Rena Jane Frew got her start, nor would I have
encountered the name of Bertha Hilton, who worked out of the Chester,
PA Radio Association station, 3ZO, had they not been mentioned
in "Popular Radio" and "Radio Digest" as part
of articles about the clubs they belonged to.
This lack of information about women is understandable when you consider that compared to their male counterparts, their numbers were small, and many did not know how to-or perhaps they preferred not to-- get publicity for themselves. Also, nearly every ham radio columnist back then was male, as were most of the officers of ham radio clubs; since it was usually a club's officers who sent information and pictures to the media, the vast majority of the amateur news was by and about the men of ham radio. Anyone reading the publications from those days could easily have gotten the impression that ham radio was an exclusively male preserve. But as Paul Harvey would say, now you are going to hear "the rest of the story".
Society's attitude about women has certainly
shifted since tile days when Marconi barred a highly qualified
and experienced marine operator, Mabelle Kelso, from working aboard
any of his ships just because she was female. Technology has certainly
changed too-- how many of you have seen (or heard}) those incredibly
noisy spark sets the early hams operated? And then, there are
the changes in terminology-- back in the late 'teens and early
20s, radio was called "wireless" or "radio-telephone",
and broadcasting was often called "sending". Some columnists
referred to ham radio as "citizen wireless", and a female
ham of any age was not a YI, but an "OW" (just as a
male of any age was called an OM). That leads me to discuss one
of the best known women pioneers, who was dubbed by the writers
"the OW of 1XE". Her name was Eunice Randall
(later, Eunice Randall Thompson), and at the age of 19, she was
broadcasting on a Boston-area commercial station owned by AMRAD,
a company which made receivers and various types of ham equipment.
The year was 1920, and she was perhaps the first woman announcer/
engineer in radio anywhere-- she was certainly the first in New
England. Eunice had come to radio by accident, having been raised
on a farm and intending to go to art school. But needing extra
money, she got a job in AMRAD's factory, where she was introduced
to the growing wireless industry. It wasn't long before she was
deeply involved with both commercial and amateur radio. To my
knowledge, she had no role models for any of this-- I have had
the privilege of meeting several of her relatives, and as far
as they recall, none of the Randalls was a "radio bug".
Yet, Eunice soon learned how to build her own station-- which
was called ER, and was operated by remote control; her parents'
farm did not have electricity, but her brother's mill did. Eunice
put up her own antenna (I saw the remnants of it--it was hit by
lightning a number of years ago, but a portion of it still stands,
75 years later, on a dirt road, near her childhood home in Mattapoisett,
Mass.), and she made a very fortuitous CW contact with a man who
became her mentor and life-long friend-- Irving Vermilya, a highly
respected ham with strong ties to the ARRL. He encouraged her
involvement with ham radio, even going so far as to write a very
positive article about her in QST (CQ did not exist in 1921).
Eunice took courses and worked hard, improved her code skills,
and got her first class license, as 1CDP. In the early 1920s,
her announcing for 1XE (which was re-named WGI in February of
1922) won her fans all over the United States, and her technical
skills (she was a draftsman and an engineer) gradually earned
her the respect of her colleagues at AMRAD. She demonstrated AM-RAD
equipment at ARRL, conventions (the only woman to do so), and
her voice was used on a Dictaphone disk that was played at the
conventions she could not attend. From 1921 through 1923, Eunice
Randall was the Story Lady, reading bed-time stories to the kids;
she also sent out code practice and read the police reports. And
of course, she was a visible presence at radio shows and ham-fests.
Had AMRAD not run into financial problems that ultimately took WGI off the air in mid-1925, she might have continued on in professional radio, but instead, she ended up working as one of the few women engineers at the New England Power Company, while remaining very actively involved as a ham-her call letters became W1MPP in 1938. For those who collect back issues of CQ, in April of 1948 she was named YL of the Month... later that year, Eunice married Ken Thompson (W1PS), also a de-voted ham, and after they both had retired, they divided their time between homes in Maine and Florida.
End of part 1. Part 2 will appear in
the June issue.
A previous issue of the ARNS Bulletin
presented the Amateur's Code. This version was written in 1928.
Larry Amann-K5TQN provided the following version, an update of
the earlier version, which has been published in ARRL workshop
1. As an Amateur I will respect the
rights, privileges, and dignity endowed upon all races, creeds
and gender. And, in doing so, I will recognize that it is not
a right but it is a privilege for all to operate Amateur Radio
equipment in accordance with the authorization prescribed in the
FCC Rules and Regulations.
2. As an Amateur I embrace the joint
membership of our beloved fraternity-sorority. And, in doing so,
I will support and protect our family of radio amateurs against
all encroachments which could threaten our dedication to the encompassing
purpose of sharing and caring for the good of all mankind without
3. As an Amateur I will be considerate.
To the best of my ability I will never use the air in such a way
as to lessen the pleasures or encroach upon the good taste of
4. As an Amateur l will be loyal. I
will extend my loyalty, encouragement and support to my fellow
radio amateurs, my local radio club and to the American Radio
Relay League through which Amateur Radio is represented.
5. As an Amateur I will be progressive,
I will endeavor to keep my Amateur Radio equipment abreast of
the technological advances in Amateur Radio Communications and
Amateur Radio Space Science.
6. As an Amateur I will be friendly,
slow and patient sending when requested, giving friendly advice,
counsel to the beginner, and kindly assistance and cooperation
for the interest of others.
7. As an Amateur my interest in Amateur Radio will be balanced. I will never allow it to interfere with any of my duties I owe to my home, my job, my school and my community.
8. As an Amateur I will be patriotic.
My knowledge of communications and my station will always be available
for the service of my country and my community.
The meeting was called to order by Pat
at 5:07 PM.
All persons present introduced themselves.
Ted read the financial report and indicated we are doing very well.
There is nothing new. The repeaters
Two applicants passed three elements.
There were six VE's present.
Thursday night 2 meter net had about
four check-ins. The Sunday morning 40 meter net was excellent.
Today's 20 meter net only had two people on.
The Company still plans to vacate Plant
5 in 2001. Moving will start in the fall of 2000. Our meeting
place should be OK until then.
It was announced that there is a place where tubes can be obtained in Melville. The place is International Components, 107 Maxis Road, (old Pl. 106) Phone 293-1500.
There was a discussion of the personnel
requirements for Field Day, which will be held on June 25, &
26 at the Grange in Islip. An expenditure of $250.00 was approved
for Field Day food etc.
Several members brought old keys. They
told the group the history of each of the keys.