Hints and Kinks for the Experimenter
January 1967 QST Article |
January 1967 QST
 Table
of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
from
QST, published December 1915 - present (visit ARRL
for info). All copyrights hereby acknowledged.
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"Kink"
is not a word you hear very often anymore in reference to having a problem
in a process or task, but it turns up fairly regularly in hobby and
do-it-yourself types of magazines as "Hints and Kinks" columns. Having
a kink in the neck or a kink in the garden hose are more familiar uses
of the word. "Kink" appears in QST, my older model airplane magazines,
in some of the Popular Electronics magazines, and likely in many others.
"Hints and Kinks" type columns typically are collections of ideas submitted
by readers explaining how they solved a particular problem or how they
came up with a new way of doing something. Some are outdated but many
are timeless in their application and usefulness. I put all the ones
here in to the latter category.
Hints and Kinks for the Experimenter
Final Tuning Knob for the Heath
"Sixer"
The final-amplifier tuning capacitor
in the Heath Twoer and Sixer happens to be a ceramic trimmer
not normally accessible from the outside of the cabinet. In
order to dip the final, one of two methods is usually used to
reach the trimmer; either the unit is removed from the case
or a screwdriver is inserted in a hole drilled in the side of
the cabinet. However, this is not always so easily done, especially
if one is working mobile. The author solved this problem by
making a built-in self-retracting knob which is always handy,
but which is not in the way during removal of the unit from
the case. As shown in Fig. 1, the knob is not fastened to the
trimmer and thus will not put any strain on the capacitor or
its associated wiring.
Fig. 1 - Details for assembling a final-amplifier
tuning control for a Heath Sixer or Twoer.
Begin the modification by drilling a 1/2-inch diameter hole
in the case directly in line with the trimmer adjusting slot.
Make a 1-inch square plate from 16 gauge aluminum stock and
drill a 11/64-inch hole in the center of the square. Drill two
1/8-inch holes in the plate for mounting the plate to the case.
These holes should be a little bit on the sloppy side for the
screws that will be inserted in them, since the trimmer does
not always return to the exact same spot each time the unit
is put back in the cabinet. I used screws from an old Command
receiver to fasten the plate to the case. Drill two holes in
the cabinet to mate with the mounting holes on the plate, being
careful to make the holes small enough to allow the screws to
self-tap.
Chuck 1/4 inch of a 1 1/4-inch length of 1/4-inch
diameter bakelite rod in an electric drill. Use a file to turn
down the diameter of the remaining 1-inch length of rod to 5/32
inch. File a screwdriver bit on the face of the 1/4-inch diameter
portion, as shown in Fig. 1. Mount the plate on the case and
insert the bakelite rod through the plate. Slip a 5/32-inch
i.d. washer over the shaft, along with a small 5/8-inch long
coil spring and a suitable knob, such as the antenna trimmer
knob from a Command receiver. Make sure there is enough compression
on the spring to keep the rod retracted. After all the parts
are assembled and the unit is installed in the cabinet, it is
only necessary to push in the knob and rotate it until the shaft
bit engages the slot of the trimmer. - Frank M. Wing, W4TUO
Thumb-Groove Indexing the Handbook
Sections of the Handbook that are frequently used by
the reader can be located quickly by filing thumb grooves in
the Handbook pages as shown in Fig. 3 and labeling these grooves
as pictured in Fig. 2. As illustrated in the second sketch,
I filed thumb grooves for only three subjects: the wire-size
table, the tube index and the general index. These items seem
to fill 99 percent of my general requirements. Other grooves
can be added at any time, but usually the sections of the book
they indicate are only of short-term use. - Norm Cucuel, K1LFH
Fig. 2 - K1LFH's method of thumb-groove
indexing the Handbook.
Fig. 3 - One method of labeling the thumb
grooves.
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Adhesive-Backed Terminal Board
Eliminates Mounting Screws
The low-profile
terminal board shown in Fig. 4 is especially useful in dense
electronic circuits where mounting space and working space are
limited, and where it may be undesirable or impractical to use
mounting screws or other hardware fasteners. The terminal board
consist of 0.012-inch-thick copper terminal strips cemented
between 0.032-inch-thick fiberglass sheets which have a thin
layer of pressure-sensitive adhesive backing. Scoring between
terminal pairs facilitates detachment of the required number
of terminals for specific applications. For soldering connections,
the copper terminals are bent outward. The boards are mounted
by pressing the adhesive backing onto a mounting surface in
the equipment package. - NASA Tech Brief 65-10396
Fig. 4 - Details of the adhesive backed
terminal board.
Equipment Feet
Football shoe cleats come in many varieties.
The hard rubber and nylon types that are threaded make good
standoffs or feet for electronic equipment. Cleats are available
from most sporting-goods stores. - Karl Hatfield, W6BXR
Grommet Cable Holder
One way
I have found to make a chassis wiring job neater is to use rubber
grommets as wire bundle holders as shown in Fig. 5. If the approximate
number of wires that will pass through each bundling point can
be predetermined, it will be easy to pick out the proper size
grommets to secure a tight fit.
- Phil MacDonald, WA1CTQ
Fig. 5 - The rubber grommets, shown here
as cable holders, should be chosen to firmly secure the wires
in neat bundles.
Phone-Jack Panel
Bearing
As shown in Fig. 6, a panel bearing
can be made from all extra phone jack by filing away the flange
on the inside of the jack and removing the excess contacts,
soldering lugs and phenolic insulation. The bearing will be
suitable for a 1/4-inch shaft if a standard phone jack is used
for the modification. -John Wallace, WA5NPE
Fig. 6 - By filing away the flange and
removing the excess parts, a phone jack (A) becomes a panel
bearing (B).
Cable Racks
I have found that hose racks, ordinarily used for
the storage of garden hose on the side of a house, are ideal
for keeping accumulated wire and coaxial cable in order. Aluminum
racks, which sell for about 75 cents each, make excellent spools
for lightweight wires and cables. Steel models cost approximately
a dollar apiece and are useful for storing heavy cable such
as RG-8/U. Garden-hose racks are sold by most hardware stores.
-Julian Lovejoy, W1BT
Calibrating Inexpensive
Signal Generators
inexpensive wide-range signal
generators that use air-core coils can be calibrated exactly,
even though they don't have an individual calibration adjustment
for each band. Stuff a length of spaghetti tubing with aluminum
foil and insert it into the coil to be adjusted. Slide the tubing
in and out of the coil until zero beat is achieved on a calibrated
receiver. For best mechanical stability, the tubing should fit
snugly in the coil. - Lou Fuentes, WB2MYN
(Since an
aluminum core lowers the inductance of a coil, the above method
of alignment will not work on those bands where the coils employed
have too little inductance. This situation can he corrected
by the following technique: Switch the generator to the band
which is in error on the high-frequency side by the greatest
percentage and fix the position of the tuning capacitor at some
convenient frequency. Unloosen the pointer and reattach it at
the correct calibration mark. Proceed to calibrate the other
bands as suggested by WB2MYN. Observe, however, that the calibration
points may or may not be true across the entire scale. Also
note that inserting aluminum foil in an air-core coil will lower
the Q of the inductor; in some cases, the reduction in Q of
an oscillator coil might cause the circuit to cease functioning.
- Editor.) |
Posted November
29, 2013
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