A new type of variometer has what is known as
A new type of variometer has what is known as a _basket weave_, or
_wavy wound_ stator and rotor. There is no wood, insulating compound
or other dielectric materials in large enough quantities to absorb the
weak currents that flow between them, hence weaker sounds can be heard
when this Wfre 99.9 Mhz In Frederick kind of a variometer is used. With it you can tune sharply
to waves under 200 meters in length and up to and including wave
lengths of 360 meters. When amateur stations of small power are
sending on these short waves this style of variometer keeps the
electric oscillations at their greatest strength and, hence, the
reproduced sounds will be of maximum intensity. A wiring diagram of a
variometer is shown at A in Fig. 54 and a _basketball_ variometer is
shown complete at B.
[Illustration: Fig. 54.–How the Variometer is Made and Works.]
Connecting Up the Parts.–To hook-up the set connect the leading-in
wire to one end of the primary coil, or stator, of the variocoupler
and solder a wire to one of the taps that gives the longest wave
length you want to receive. Connect the other end of this wire with
one post of a .001 microfarad variable condenser and connect the other
post with the ground as shown in Fig. 55. Now connect one end of the
secondary coil, or rotor, to one post of a .0007 mfd. variable
condenser, the other post of this to one end of the grid coil and the
other end of this with the remaining end of the rotor of the
variocoupler.
[Illustration: Fig. 55.–Short Wave Regenerative Receiving Set (one
Variometer and three Variable Condensers.)]
Next connect one post of the .0007 mfd. condenser with one of the
terminals of the detector filament; then connect the other post of
this condenser with one post of the .0005 mfd. variable condenser and
the other post of this with the grid of the detector, then shunt the
megohm grid leak around the latter condenser. This done connect the
other terminal of the filament to one post of the rheostat, the other
post of this to the - or negative electrode of the 6 volt A
battery and the + or positive electrode of the latter to the other
terminal of the filament.
Shunt the potentiometer around the A battery and connect the sliding
contact with the - or zinc pole of the B battery and the + or carbon
pole with one terminal of the headphone; connect the other terminal to
one of the posts of the variometer and the other post of the
variometer to the plate of the detector. Finally shunt a .001 mfd.
fixed condenser around the headphones. If you want to amplify the
current with a vacuum tube amplifier connect in the terminals of the
amplifier circuit shown at A in Figs. 44 or 45 at the point where
they are connected with the secondary coil of the loose coupled tuning
coil, in those diagrams with the binding posts of Fig. 55 where the
phones are usually connected in.
Short Wave Regenerative Receiver. With Two Variometers and Two
Variable Condensers.–This type of regenerative receptor is very
popular with amateurs who are using high-grade short-wave sets. When
you connect up this receptor you must keep the various parts well
separated. Screw the variocoupler to the middle of the base board or
panel, and secure the variometers on either side of it so that the
distance between them will be 9 or 10 inches. By so placing them the
coupling will be the same on both sides and besides you can shield
them from each other easier.