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ANTENr~AS- HAM BAND
144 MH z 2 meter band , omnidirectional,
horizontally po ­
larized, use - Fixed & Mo bi le
Ham , Civ il Defense and
M .A. R.S. A ll sol id copper. RG
8/ u cable.
STANDARD one or two ANTENNAS
HIG H GA IN fo ur - e ight an te nnas
o ne 1.3dB / dipole S 19 .9 5
two 4 .3 dB 39 .90 w ith cable -+ con n. $ 49.40
f o u r 7 . 3 J 6 79.80 wi th cabl e -+ co n n. 10 4 .8 0
e igh t 10 .3 d B 1 59 .8 0 with eer-ie -+ c o n n . 208.54
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Gilian & Company
105 O rchard St.
Wa tertown, Ma ss. 021 2 1
loop osc illator. I favor t he thir d-me ntioned
mod e, with the tone adjus te d to the
500 - 1000 Hz region. T hen an appro ach to
a met allic o bject will cause a rise in pitch.
Th is locator is entirely f ree of "pulling"
betw een th e two oscillators whic h, in
co nventional locators, often causes a
mar ked reduction in sen sit ivity .
T roubleshooting
If, wit h the transistor radio strapped to
the reference oscillator bo x . adjust ment of
th e variable capacitor docs not bring for th
th e audio tone, bot h the reference oscillator
and the loop osc illator should be
checked for osc illati on . This is easily accomplished
by means of an oscillos cope.
Probe th e base of Q I and Q2 ; if th ere is no
eviden ce of oscillatio n. ma ke a method ical
investigatio n of the co nnect ions, th e components,
battery pola rity, etc.
Th e most probable cause w ill involve
th e ability of th e referen ce oscillator to
tune sufficiently close to the frequency of
the loo p osci!lator. This could co me about
if th e Myla r capacitors associated wit h the
tan k circui ts deviate more th an th e pre-
14
Additional Not es
Th e cover plat e for th e reference oscillato
r should be made of fibe r glass, Vector
board , Lucite, or other insulating mat erial.
Metal must I/ O ! he used,
Pol ycarbonat e or po lysty rene cap acitors
of the specified tolerance co uld be used in
place of the Mylar capacitors in the tank
circuits of both oscillators . However, the
mctalized versio ns of any of th ese dielectrics
should not be use d.
Th e fact tha t no shielding of the loop is
required can be readily demon strated by
putt ing one's finger on th e " hot" end of
the loop . A negligible change in th e pit ch
of th e audio-tone is pro duced . This, of
cou rse ste ms fro m th e ex tre mely lo w im pcdan
ce of the loop . Conversely, it is, as
desired , very sensitive to electromagnetic
disturbance of its resonant frequency.
.. . W6HDM ·
73 MAGAZINE