b. Selection or Colls: For most tuned circuits it may be more
convenlent to utlllze lnductlve COUpllng. A simple
Frequency rar,ges are marked on each coll illustration or a typlcal clrcult 1s show in Fig-
except ror the two hlghest rrequency coils. Fre- ure 2. This represents a common by-pass dirricuity
quency limits or the corresponding scales are whlch gives rise to dead spots in high frequency
marked on the oscillator unlt. Arter insertion or
the desired coll, It 1s advlsable to set the tun- receivers and transmltters. Maxlmum coupling (and
lng knob to mld-scale, and then adjust the sensl- largest dlp in grid cprrent) ~1.11 result with the
tlvlty knob to approxlmately 50 on the grid cur- axis or the oscillator coil at right argles to the
rent meter. Normal varlatlon of the grld current current flow. For accurate checking or the reson-
wlth tuning wlll then usually remaln on scale over ant clrcult frequency, the coupling should be
the entire range or that particular coil. (Note: loosened by Increasing the separation between the
oscillator coil and the clrcult under test until
on some low rrequency coils it may be necessary to only a moderate dip ln grid current (10 to 2W)
readjust the sensltlvlty knob at the extremes of results when tunlng through resonance.
the tunlng range. )
Some types or tuned clrcults are well
shlelded magnetically, so that It is difflcult to
c. Adjustment or coupllng utilize lnductlve coupling. Flgure 3 illustrates
Either inductlve or capacitive coupling of such a circuit. Thls co-axlal line resonant cir-
the 59 can be made to clrcult under test. cult 1s self shielding and Of sulflciently high
Figure 18
STORAGE POSlTlOH OF COILS
6. |
ACEC
OTHERS
