The Challis messenger. (Challis, Idaho) 1912-current, 1925-08-05
BY FRANK REIcHmANN. 3. g.. E. M.

BY FRANK REiCHMANN, 3. s.. e. M
Improvement In apparatus. rather
than new and revolutionary circuits
Is responsible for the rapid increase
In efficiency Of our radio receivers.
This Is accomplished by the elirnina-
tion OF losses. balancing up of cir
cults, and the combining of straying
capacities. improvements that are the
result OF months of experimentation
and practical test work on the part
of far-seeing radio engineers, and very
rarely stumbled upon OF. accidentally
discovered.
The latest radio Improvement, the
helchmann doughnut coil, may at
FIRST glance seem to be the result
OF few minutes playing with a coil
or wire and broomstick The real
facts Of the case are that the coil
ID the product OF six months inten-
sive work on the part of three radio
engineers seeking new type of in
ductance that would be free from the
drawbacks commonly associated with |
coils Pioneering In a new field. with
out the successes or failures Of pre-
vious experimenters to guide them.
the pitfalls and blind alleys along the
way were thoroughly investigated
while slow progress was being made
toward the ultimate coil.
Corrects Loss Of Energy.
In ordinary layer-wound coils con-
siderable loss of energy takes place.
due to the fact that. through a con-
denser action, the current tends to
travel between adjacent wires as well
as through the conductor itself. This
condenser action is due to the self
or distributed" capacity of the coil.
by the paraIleling Of the con-
ductors. In the low-loss and honey
comb-coll type of windings, this is 6
to a certain extent, by run
hing the wires at right angles to each
'ther and crossing at intervals.
the first experimental coil form was
made by cutting out a circle of card
oard with little protrudlng tabs on
he inside and outside edges. A mar |
ow strip of pasteboard was bent
round In the form of circle and
asted on each side of the fiat circle
The original Idea was to wind the
Ire around the form. hooking 1t over
e tabs at Intervals When this coil
as constructed and tested, 1t was
und to be no better than present
lis, due to the fact that the wires
n parallel to quite an extent. max
: the distributed capacity of the L
Il high.
he next attempt was made by wind
! the wire around the form, disre-
riding the protruding tabs, so as TO SIX,
Ike closed coll, supported by the ed
lr edges OF the cardboard strips. the
Is coll was an Improvement, so hal
ger forms were tried and II was Of
'ided TO continue to experiment VIII
III this type Of coll. 7
the wire over and over the cou
cular form by hand became rather fra
orlous, so one of the engineers wal
"a winding the coll on a straight tior
m, then removing and bending tbe turl
In circle to form toroId coil swu
was difficult to keep the wires In it o
&c with this method, so he tried set
ming the wire In at every other man
or the winding form with HE Olso
NIB nall, so that string could be
'aded through the indentatIons z.
so hold the coil together when liz
form was removed Measurements
MS coll showed decided improve n.
over other types, as the greater ~
e OF the losses due to the dis qu,ie
lted capacity and coil support CT CT
rb. r,., on to ad
:. 'e''peo. broad
this manner In search of tho sons,t
II diameter. Size of wire. and crvsto
al overall Dimensions of the cot 10
consistent with low losses and eyer
Inc coils held lent f