The Bozeman courier. (Bozeman, Mont.) 1919-1954, 1923-01-31
MB0
interference OF
RECEIVING SETS
Each, When Tuning for Distant
Station, Acts as a Continuous
Wave I%ransmltter.

W9 Rave EAUtdlACQ NAA0h AN |
GUS, fairly steady whistles, usually
heard while tuning for the distant STA
tons. was due to a combination OF
the carrier waves Of two stations
which were very nearly on the same
wave length. There Is another series
Of whistles always present which very
much resemble the whine Of a mos
quito both In tone and amount OF an
noyance produced. These are caused
by the receiving sets OF other listen
ers. Every receiver using a-vacuum
tube detector with a regenerative cir
cult is a potential transmitter. In
fact 1t contains all the essentials Of
q ~radiophone transmitter OF q small
scale.
The detector tube when oScillating
produces oscillation exactly similar to
the carrier wave Of the ~radiophone
stations. The frequency or wave
length of this wave can be varied by
changing the tuning Of the receiving
tuner.
The usual procedure in tuning for
q distant phone station Is as follows:
Put the detector tube In an osclllating
condition after the tuner has been ad-
justed near the point where expert
ence has taught us to look for the
~broadcasting stations, then move the
dial slowly across the approximate
point where the stations are usually
heard. The carrier waves are located
by a whistle which starts at the upper
limit Of audIbllity and goes down the
scale until 1t becomes so low that 1t Is
no longer a note. At this point the
set is in exact resonance, and If the
ticker, coupling. or plate tuning in.
ductance is decreased until the detec-
tor tube stops oscillating, the very
best adjustment is obtained for recep'
ton Of that particular station.
Unfortunately while this listener Il
going through this operation his re
celving set Is acting as a continuous
wave t~ransmitter, and Is producing
some inharmonl0us walls In thu
phones of his neIghbors who happeI
= to be already on the wave Of the sam
station. The continuous wave sen
l out by the receiver combines with tn
carrier wave Of the transmitting sta
: ton, producing an audible note. I
: the operator could tune his set as sin,
ply as was described above Their
Q would be very little interference, Blu
he usually whistles back ard fort
across the wave OF the transmittin
station several times. Often severe
listeners who have been getting th
concert perfectly will get restless bl
tween selections and get thelr tube
to o~scillating and whistle up and dow
q few times.
Ia All listeners should be very caref'
Il to keep their detectors In a non-osci
y lating condition as much as possib
Is to reduce this annoyance of interfe
u ence between receivers.
'e Opinions seem to vary c~onslderab
In regard to the comparative amour
Of energy indicted into the antenna |
IS the ''slngIe circuit or conductive
a coupled, and the "three circuit"
inductively coupled receiving set.
1g Previous to the introduction Of Il
T. single circuit very little trouble b.
IS been experienced with beat not
a from receiving stations This was
doubt due to the fact that receivi
sets were rather few and far betwee
also up until a few years ago the
~ was a very small percentage Of c.
telegraph and phone stations so til
there was no reason why an anate
should keep his tube In oscillatl
condition. On the contrary, he "
xxi very careful to keep 1t just below 1
zee oscillating point, that being The M
mt sensitive adjustment for spark sigma
ny With the telephone and C. w. te
graph transmitting stations, 1. e., Il
= transmitters. came the single Giro
- tuner with its extreme simplicity
adjustment, which was so wen ada
ed to the very sharp tuning of
new transmitters. And with the
vent Of these new transmitters ca
the necessity for making the detec
tube oscillate In order to locate a {
tion ON the scale Of a receiving tur
Naturally then the interference
tween receiving sets became not
able at about the time that the sir
circuit sets became numerous, and
helped to prejudice the minds Of
radio public against this type of
eeiver. However, the fact that
single circuit arrived at about
same time with the Interference was
no means the only reason for belle,
this tuner to. be the main cause
the trouble.
For instance In constructing g sh
circuit or conductively coupled tt
the dlficulty is in obtaining regen
ton at all points on the scale. .
sen to show that there Is more
sistance In this circuit than In the
ductively coupled type. The q
point Of difference Is the c
coupling to the antenna. Being
ductiveiy coupled, the coupling
the antenna circuit Is at maxir
at all tImes. This causes the
diatlOn resistance 10 be high. W