The Washington times., 1924-06-09
INTEREST. RISES
. IN SHORT WAVE
TESTS
Number Of Amateurs in Europe
Operating on 100 Meters
Have Been Heard Here

ton made in recent transatlantic
tests. and by re-broadcasting Of pro.
grams transmitted on 100 meters
from Pittsburgh. to Hastings, Ne.
braska and to Cleveland, Ohio. Sta
tons in Cleveland and Hastings
have been unable to receive the
eastern programs because Of local
dead spots on the normal wave
lengths, so the 100.meter transmits.
sion was tried out with remarkable
success, 80 much 80 that the re-
ceived signal was constant enough
to be re.broadcasted.
In England, similar difficulties
were encountered in the reception
OF programs from America. Sig.
mails faded badly on the normal
wave lengths. but It was observed
that those on the lower scale were
more consistently good. Pursuine
the theory further, that the hiSher
trequencies were less influenced NV
absorption, the engineers made =
radical departure from rSrecedert
and reduced the wave to Inn metSrs
TINS wave proved to be the happy
ueoium, ana the British stations
now re-broadcast programs, received
on 1OO meters from Pittsburgh. for
the benefit Of listeners in Great
Britain. "'
Building Not Difficult
Building the 100 meter rece,var
Is not a difficult task.
Inc tuning coil has two wind.
tngs, separated one-quarter Incl.
one OF ten turns, which IL the
primary, and the other Of 20 turns,
Wnicn Is the secondary, Use No
IL single cotton covered wire ana
WIND evenly. watch out for kinks
The tube, on which both colts ara
wound, is three inches in diameter
ana four inches long, and NAV he
made OF cardboard or bakelite
The variable condenser. which "a
an eleven.plate type, .00025 micro.
farad condenser, with vernier. must
be designed for low dielectric
losses, which may cost a little more
than the average but il a GOOD
investment. This condenser In con.
nected across the secondary. with
the rotor connecting to the grid
condenser and the stator to the
positive side Of the "a" battery.
The Grid Condenser.
The grid condenser must have a
mica dielectric and q capacity OF
.OOO1 microfarad. The grid leak.
tubular type, has 2 megohms resist.
ance.
The instruments are mounted on
a nara rubber or bakelite panel.
inches by 10 inches. Line the panel
up with a pencil FOR instrument
layout. Center the binding post
holeS three-Quarters of an inch
from the edge. Center punch Deep
ly. as this will keep the drill from
slipping off, and make the shaft
holes slightly oversize to prevent
binding. Countersink the two screw
holes for the variable condenser.
Before mounting the instruments,
attach the shield, which Is q strip
OF tin or copper foil, mounted be.
hind the condenser and connected
to the ground binding post. This
shield is attached 20 the panel with
shellac or glue. Scrape away the
foil around the holes, so that the
instrument will not come in contact
with 1t. This is extremely impor'
tant.
How to Wire It.
Wire the set with square bus bar,
covered with spaghetti wherever in.
sulation Is necessary. Do not de-
part from the Arrangement shown
OF the apparatus, because no lati-
tude is permitted In the construc-
ton Of this set for 100 meters.
Do not under any circumstances
ground the filament or plate bat
terry. This would short circuit the
fixed condenser, providing q path
for the plate current direct to the
filament, which would burn out.
The set will work with any stand
ard tube, such as UV-199, WD-l2
UV.201-A, or UV-200. The first
tube works the best, however, at
this frequency Of 100000 cycles,
because of its low internal capacity.
Operating the 100 meter one.
knob receiver is simplicity ITSELF
turn one dial and get your station.
However, do not be surprised at
the silence which may greet your
ears, 30 to speak, when you try It
out first. Tuning at this extremely
high frequency Is. naturally, sharp
er than along the lower bands, and
must be done with patience.
Test 100 Meter Wave.
A great deal Of sexperimenting Il
being carried out on the 100 meter
wave and lower, to which the set
will respond nicely. Interference is
a negligible factor at present on
this lower band, and extreme dis.
lance reception can be accomplished
with ease. Some Of the amateurs in
Europe are transmitting on 100
meters and arg being heard on
this side, but on telegraph, not
phone, and these should be heard
under favorable conditions, with
suitable application.
Using the UV.199 tube and fila.
ment adjustment, with the 30 ohm
rheostat, is not critical. The rheo.
stat can be used to control reReue.
ration when 1t is difficult to tune
out the whistle with the vernier of
the condenser.
In case the set does not reHene.
rate, reverse the leads Of the secon.
dairy to the grid and filament.
CEEHC lA1ORlR AARAE Aa0A--