August 1935 Short Wave Craft
Wax nostalgic about and learn from the history of early electronics. See articles
from Short Wave Craft,
published 1930 - 1936. All copyrights hereby acknowledged.
You might not have the need
for a variable capacitor made from a match box and a couple strips of tin foil,
but there are plenty of other "shortwave kinks" offered here that could be of use to you when
the preferred part is not available. For instance, maybe a transformer exhibits an
audible hum because of improper construction, or maybe a vernier dial is needed
for an adjustment knob; homebrew solutions are offered for both. The adjustable
capacitor idea is an "outside-and-inside-the-box" solution (pun intended) that
could come in handy. In all, there are 11 tips from way back in 1935 offered
by fellow radio enthusiasts, and printed in Short Wave Craft magazine.
$5.00 for Best Short Wave Kink
The Editor will award a five dollar prize each month for the best short-wave kink
submitted by our readers. All other kinks accepted and published will be awarded
eight months' subscription to Short Wave Craft. Look over these "kinks" and they
will give you some idea of what the editors are looking for. Send a typewritten
or ink description, with sketch, of your favorite short-wave kink to the "Kink"
Editor, Short Wave Craft.
$5.00 Prize Matchbox Condenser
A cheap and easily constructed variable condenser can be made with a safety matchbox
and a few short pieces of tinfoil. In the drawing we see that two pieces of tinfoil
are used to form the two electrodes of a variable condenser. One piece of tinfoil
is glued to the top of the box frame and the other piece is glued to the bottom
of the sliding portion of the matchbox.
A binding post is used on each of these strips of tinfoil in order to facilitate
connections. If desirable, a scale can be marked on one side of the sliding member.
This is clearly shown in the drawing. When the box is entirely collapsed the capacity
of the condenser is maximum; by sliding the inner section of the box outward the
capacity is reduced. This is a handy Instrument and many readers of "Short Wave
Craft" will find various uses for it. - Gilbert S. Lowry.
A short length. of rubber hose can be used to form a very simple shock absorber
to eliminate vibration in a radio receiver. The drawing clearly shows that the hose
is tacked or screwed to the base with the screws or tacks in such a position that
they will not rest upon the table or interfere with the cushioning action of the
rubber hose. This kink is especially useful with battery receivers because these
tubes are usually quite a bit more microphonic than the heater type of tubes. It
can also be used in conjunction with the transmitters where vibration is liable
to cause a poor signal by modulating the note - Francis P. Srebro.
Razor Blade for Cutting Tubing
Probably the most difficult part of short-wave experimenting is cutting bakelite
or other compound tubing the proper length for coil forms. Usually a hack-saw blade
is used and in many cases a very jagged and uneven cut is made. However. by fastening
a razor blade or knife blade in the vise and placing the tubing alongside of it,
an accurate cut can be made. First wrap a piece of paper around the tubing in order
to mark it where the cut is to be made. By squaring the edges of the paper, the
mark on the tube will be perfectly square. By rotating the tube in one direction
slowly and keeping the blade on the mark, accurate lengths of tubing can be cut
with very little difficulty. The drawing clearly shows how this is done. - W. H.
Simplifying Coil Construction
Many of the readers of "Short Wave Craft" have spent considerable time in wiring
homemade plug-in coils. By using the scheme depicted in the drawing, the correct
number of turns can easily be found. The pin is soldered to a short piece of wire
and can be pushed through the insulation on any turn. When proper results are obtained,
you can remove the unused turns and your coil is finished. - Howard Sig-mund.
Eliminating Transformer Hum
Many fans who have all-electric short-wave receivers using power transformers
are troubled by a loud buzzing noise in the transformer itself. This is usually
due to either loose windings or a loose section of the core. In most cases where
"E" type cores are used, the center leg of the two outer laminations makes all the
noise. This can be stopped quite readily by removing the frame or mounting bracket
of the transformer and wedging a small piece of wood between the winding and the
core. If you will refer to the accompanying drawing you will see how this piece
of wood is tapered in order that it may be easily inserted. - Francis P. Srebro.
Field Supply for Dynamic Speaker
Here is a very simple method of obtaining power for the field of a dynamic speaker.
Although this is not original to the writer he thought it would be of interest to
the average short-wave fan. A single 25Z5 is used in a halfwave rectifying circuit.
The physical drawing shows just how the connection should be made. The smoothing
condenser across the output of the rectifier can be anywhere from 4 to 8 mf. and
is an electrolytic having a working voltage of somewhere around 200. Heater voltage
for the 25Z5 is furnished directly by the line through the 290- to 300-ohm resistor
which is built right into the line cord. - W4ED.
How to Make Stranded Wire
At some time or other, many short-wave fans, like myself, have been in the need
of stranded antenna wire., By dismantling an old power transformer and unwinding
the primary, quite a long length of stranded wire can be made. The drawings clearly
show how the wire is first wrapped around two posts driven in the ground. The distance
between the two will determine the approximate length of the finished cable. After
the wire has been wrapped around the post remove one post and fasten the wire into
a hand drill. Then by simply turning the crank handle of the drill, the wire will
be twisted evenly. - William J. New.
With the increase in popularity of metal panels and chassis, many home constructors
will be in need of a simple, yet effective circle cutter. The drawing clearly shows
how one of these can be constructed from an old file. In use this cutter saves considerable
time inasmuch as a hole can be cut in less than one minute in ordinary aluminum,
and two to three minutes in steel panels. - Henry Larrabee.
Code on Cards
Here is a kink that I think will help the short-wave fan who has just started
to learn the code. Cut twenty-s ix one-inch squares out of' cardboard. Next, mark
on them the translation, of the alphabet from A to Z in the continental code. Also,
put a small arrow at the bottom of each card so one will know which way the card
is to be held. We now shuffle the squares just as a pack of playing cards, and one
by one take each card, identifying the letter it represents, and place it apart
from the unpicked ones. In this way one gets to know the letters from their continental
translation instead of forming the habit of letter to code. As soon as one knows
the letters, cards of the numbers can be made. - Norman Esplin.
Old Car Radiator Used for a Ground
Being unable to obtain a good ground, I finally hit upon the idea illustrated
in the accompanying drawing. I obtained an old radiator which had a good many leaks
in it. After fastening a pipe to the filling hole on the radiator and soldering
a wire to the other end. I buried the entire assembly in the ground four or five
feet below the surface. I then proceeded to fill the radiator with water. This,
due to the holes in the radiator, seeped outward and made the earth surrounding
the radiator quite moist lowering the ground resistance considerably. The lead from
this ground to the receiver was kept as short as possible, and really excellent
results have been obtained. I am passing this information along to the readers of
"Short Wave Craft" in the hope that it will be of material benefit to them. - Edwin
Homemade Vernier Dial
Nearly every short-wave fan who builds his own equipment gets the greatest amount
of fun out or building it rather than listening to the short-wave stations. The
experimenter will find this dial easy to construct and very handy in operation.
There are two knobs, one which is attached directly to the main shaft and gives
a direct drive for rapid tuning, and another knob which drives the outer edge of
the large disc for vernier tuning. All the parts of this simple vernier dial can
be found in the shack junk box. - G. E. Tovey.
Posted April 20, 2022