The Carbon County news. [volume] (Red Lodge, Mont.) 1924-1931, 1928-02-02
Amateur RadiOphOne
BY ORVILLE w. VIERS
Owner and operator of Station
7AAT-7QT; Section Communica-
ton Manager of Montana


| have experimental with telegraphy
the most, but have done little along
the phone line also.
When using radiophone more power
is required to cover the same distance
than when radio telegraphy is used.
For this reason, that of the power,
there are not as many amateur ra
diophone transmitters as there might
be.
Under normal conditions a seven
and a half watt stransmitter may be
heard in most every country and con-
tinent, if telegraphy is used instead of
radiophone. But, for radiophone to CO.
yer the same distance it would take
from 500 to 1000 watts, and possibly
more, all depending on the location of
the transmitter. This amount of pow
er requires much money and this is
the reason or one of the reasons ra-
diophone stations of the amateurs are
not heard in every corner of the
world as are their telegraph signals.
If one intended to go to the trouble
and expense of installing 1000 watt
station it would be we'll worth the
while to install it for biography in
stead of radiophone. I'm sure l would.
During November l did little ex-
perimenting with low powered phone
transmitter and had good luck for the
power I was using, which was seven
and one-half watts. l applied 900
volts of pure direct current to the
plate. My voice was heard in Ken
lucky, Iowa, Pennsylvania, Califor-
MIA, Washington, Oregon, Montana,
Wyoming, Colorado, North and South
Dakota, Illinois, Ohio, Texas, Okla
homa, Nevada, Arizona Utah, Mime
sofa, Wisconsin and Kansas. In all,
reports received from these states my
signals were loud and the meditation
perfect.
One thing very essential for radio
phone is direct current power supply
for the plate of the bue, or tubes, as
the case may be. The city light mains
are supplied with 10 volts of alter
mating current which changes cycle
60 times second. This, when used on
radio transmitter, produces a very
rough note which reminds one of gil
gantic sawmill, blaring and buzzing
roughly.
I knew that | could never use a
phone with this rough note and even
telegraphy would not be complete
success. So thought of a rectifier to
change the cycle Of the current. There
were several different kinds of recti-
fiers, so | had to decide just what
kind would be best for what | wanted.
l saw synchronous rectifier adver-
tised SO | considered it. figured that
since the current was rectified by two
revolving metal discs driven by mo-
tor, it would be too hard to filter and
change into direct current. Next l
took the different types of tube recti-
fiers. These would all be too hard to
filter and the voltage drop would be
200 at full load. Then l took the chem
ical rectifier. This would only half the
voltage drop and would be very easy
to filter. constructed So jar con-
tainer and put each jar in its place.
filled each jar with a solution of
borax and water, then placed in each
jar lead and aluminium strip or
plate, and connected them together so
the jars would be in series to re-
ceive the load. | applied 5000 volts
at first and tried the transmitter. The
beat note was improved. 1t was
smoother because the cycle of the cur
rent had been changed to 1870. AL
though the note was smoother and
pleasing to the ears, it was still too
rough for phone work. then set to
work to build filter for the purpose
OF taking the ripple from the current
bought 100 Henry choke coil and
bank of filter condensers. I placed
the choke coil in the positive lead from
the rectifier and hooked the filter
condensers across the positive and
negative leads to the transmitter. l
listened to the beat note again and
found what l wanted. A high pitched
whistle, pure, clear, and bell-like in
tone. | then placed microphone in
the transmitting circuit where l fig
ured l could obtain good meditation.
(As this was only to be an expert
| ment | did not bother to build mo-
dulator and speech amplifier.)
| started the transmitter by closing
the line switch which turned on the
two large transformers, one for light
ing the filament in the tube and the
other for supplying the 5000 volts to
the rectifier. After closing the key
switch l spoke into the microphone.
Hello, hello. This is 7AAT at Red
Lodge, Montana calling. Anyone hear
ing this call is requested to give me
a call" l repeated this few times
and then signed off. was now ready
to listen for an answer to my call,
my nerves were tense and my ears
tuned to the highest possible pitch of
accuracy. Suddenly | crossed loud
signal, while twirling the dials. I lis
tened and heard my call letters, be-
ing sent in code. After few seconds
of calling me the station signed his
call, Ssh, and then he signed off. l