Evening public ledger. [volume] (Philadelphia [Pa.]) 1914-1942, 1922-05-18
n Panel for Your 4udion Bulb

Tho panel on which .ha controls of
the audion bulb are mounted Is one
piece Of radio apparatus that any
great trouble and has no complications.
! made the one shown in the illustra-
tion in half an hour.
Let me say right here that strongly
advise all amateurs to ndoDt what is
raled the "unit" system Of building
apparatus il they intend to make their
own and experiment with different
kinds.
This "unit" system simply provides
little case for each separate piece Of
apparatus and each case is exactly the
same size as the others.
have found the most convenient size
to be six inches all around. That is.
the front board. Or panel. IS made six
inches by six inches. the base. on which
Instruments are mounted. is board
the same size and ! put another board
the same size up in back. II ! see a
diagram Of new hook-up ! take tn"
units called for and stand them side bv
side or one on top OF tho other and
fronts Of the panels by wires as the
diagram calls for.
have n variocoupler in such case
a spider web coupler. couple Of vari,
able condensers, my "B' batteries and
nmplifiers and everything else used
around a radio set. Thus. when ! try
new hook .up merely build hous"
Of blocks and it looks neat and is most
convenient for wiring. SO lets start
right now. in these talks. to consider
that We are going to build in units siA
inches by six inches.
Ordinary board will do for the base.
but the front panel should be one of the
Insulating substances like formics or
bakelite. The first thing to do with
this audion bulb control unit Is to glue
tin foil or copper foil over the entire
back of it. The audion receiver has
very remarkable and very inconvenlen
disease known as body capacity.
Your own body is a condenser and whcn,
you turn the knobs to tune in signal
that body capacity enters into the cir
cult. The consequence ia that after
getting the signal loud and clear, when
you take away your hand and lean bacE
in your chair the signal disappcars.
! Nou have taken the capacity of youI
body out Of the circuit
| This tin foil backing Of tho panel !,
! in contact with the binding post shown
in the middle Of tho lower part of the
/ panel. When you are ready to hook
! this unit to your set you run wire
from this binding post directly TO yo,l
! ground wire and thus your body
capacity is always grounded and il
not so likely to Interfere with youl
| tuning. This tin or copper foil backing
! should be done to virtually all Of your
units.
Before mounting the panel bore HOES
for the six binding posts at the left
the two at the right. the on" just spOk"l
Of, the shaft Of the "rheostat. the
switch blade and the two contact points
Then turn your panel over and cut th'
tin foil away from around all these holc'
except thni which holds the bindin.
post for tie body capacity ground.
That post must make good contact Will
the foil You should then take a large
bit and bore the peep holes whic!
allow you to look nt the bulb and so
how it il burning. TIL" foil need not b.
cut from around thrs" holes. but mus
be cleared from III" others TO avoid th'
danger Of bar" wire touching 1t AM
grounding tn" whole set
On the back Of IN" panel mount th'
rhcostat as shown. II is wise t" put {
heavy piece of cardboard between it am
the panel SO that no metal on the rheo
stat can touch the foil. Then You ar'
ready to wire up your bulb socket. AM
it Is usually necessary to do this before
screwing it to the base board.
Mark your binding posts as shown ir
the front view Of the panel. Cs'