The Ely miner. [volume] (Ely, Minn.) 1895-1986, 1924-11-07
BY LEWIS [. ELLIOTT

A perplexing problem facing the
] radio fan of today is the elimination
Of interference from broadcast sta
! tons in and about a great metropolis.
With its six or seven powerful stations
| in operation and whose wave lengths
are somewhat close together, it is
quite difficult to tune in to a given
from the other transmitters. This
can be more related to the operation
Of WEAF on 492 meters and the new
! station WNYC on 526 meters would
show only "a meters in difference.
! A combination wavemeter and filter
, consisting of precision vernier con-
! denser and tapped coil or inductance
has been available to radio expert
mentors for some time. With this in
strument the broadcasting listener can
| readily check the wave lengths of
! broadcasting stations or of the dot
and dash Geographic signals which
may be interfering with his programs
/ The device may also be employed eff
fectiveIy as a radio filter to reduce
interference from undesirable stations.
! The use of the instrument as a
! filter is shown in the accompanying
| diagrams. This device will improve
the selectivity of any receiving set.
This Improvement is more noticeable
when used with the single circuit type
of receiver than with the inductively
coupled type. Its use with crystal
receiver is quite simple.
| There are two particular methods
of using this instrument as a filter;
one is called the series method, the
other the parallel filter. In Figure l
| is shown the proper connections for
use as a series filter When troubled
| by interference from nearby broad
casting station, break the antenna lead
! to your receiver and insert the coup
! ling coil as shown In. Figure /.
Setting the Coil.
Set the switch on tap (eight turns
in the coupling coiD and slowly rotate
the condenser knob until the desired
signal decreases, vanishes and again
! increases. Using the small knob, pass
slowly back and forth over this point
until the position for minimum inter-
fering signal is located. The filter is
/ now set for this one interfering station
I; tits wave length in meters can be read
! from the condenser scale). Both the
interference and the filter may now be
forgotten and the receiving set tuned
to distance stations in the usual
manner. ---.
The parallel filter is used to reduce
, interference from spark transmitters,
static, A. C. hum and similar sources.
1t will also allow you to tune out sew
eral local stations broadcasting stimuli
(; taneously and receive from a broad
casting station of wave length differ
ing by only few meters from the
+; nearest interfering wave.
! Connect the parallel filter as shown
in Figure 2 Set the switch on "open"
and tune your receiver TO the desired
station. Then move the filter switch
! to contact s and all signals will dis
] appear until the filter condenser is adj
| justed to exactly the wave length Of
the desired station. The wave length
markings on the dial are help If the
:: desired wave length is known. Listen
| closely for your station while slowly
| moving the filter condenser back and
! forth over the approximate wave
! length of the station. Use the small
/ knob and tune carefully, because one
half of one degree on the condenser
/, dial Is enough to tune the desired sta
| ton in or out.
How to Get Results.
Most people are not accustomed to
I the kiphly desirable sharD tuning