Heathkit IM-4180 - Page 13

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ity in 1 the lower V VHF ance isa approximately 1
millivolts (see “Specifications,” Page 55).
SCOPE jacks: Demodulated audio signals can be
coupled from the two scope jacks (signal +
ground) to the Lope of an oscilloscope. This
output is in the order of 13mV/kHz and is
superimposed on a DC voltage which is propor
tional to the intermediate frequency.
BATE 4 area of the meter.
5
Connect an FM RF signal source to the RF
INPUT front panel jack.
mo: at INIT TTINIT 7Asten 1 tnAne An the feant
opel the FINE LUING Control inQ@ex Of) hie irOfit
nanel diagonal line
Qr oO
Turn the GAIN control fully clockwise.
Press the TUNE button in.
weet en Pane epee RIATO, TL. Mota at,
Carrier irequency. INULE. Lie Veviation Met r
local oscillator frequency is at 0.2 MHz above
and below the incoming carrier frequencies. If
the meter pegs at the high end, turn the GAIN
Sane teas mania Soe Sear Pee, serneT TRTT
control to bring the polnter within the LUINE
area on the meter dial. Retune, if necessary for a
maximum meter indication. In tuning to the car-
rier frequency, two peaks _ be observed. To
Fhter eviat a adtinag
tune for a positiv 6 aéviation eaaing, select the
lower-frequency peak coed. To tune for a
negative deviation reading, tune to the higher
peak. These peaks will occur at 0.2 MHz above
Lh an alacsr the rarriar i ran ONT
anda vDéeéiow tne Ca@lrivr LIOyQuUuehcy.
aR
When you operate the Deviation Meter at higher
frequencies, if you cannot sie te minimum
aval indiratinn nenceed as mL sara
EVE. iMGication, PTOCceea a5 trOu0WS:
a. Set the Meter to the desired frequency.
Fundamental frequency (from 25-50
ae an | 94 9 MATTIAS
sCai€) — —~ 31.4 iVilldé.
Added frequency: 500 + 31.2 =
531.2 MHz.
Subtracted frequency: 500 — 31.2 =
468.8 MHz.
nee an a harmonic frequency ee the unit
under test; incorrect deviation measurements
could result.
8. In high VHF and the UHF bands, the positive
and negative peaks will appear to kes very close
together. Use the PONG LUING con 4, PIESet at
midrange with the knob index, to nie the
1 i ! l ) _ ) "
I e ation signal is
ore than 5 kHz, the modulation
9. Press the appropriate kHz DEVIATION range
pus shbutton and read the amount of deviation
from the meter. NOTE: The 2 kHz range circuit
contains a 1.5 kHz low-pass filter to assist in the
elimination of high-frequency noise at the lower
modulation frequencies
10. Ifdesired, you may connect an 8-ohm speaker or
a headset to the SPKR output jack on the front
Sea ra reas De fy ee me eeee | mavna mlws Deroh the
pale. Use a single-pole phone piug. P LOL LEG
de-emphasis switch to the correct setting: 75 ws
for standard broadcast applications, 750 ys for
two-way radio applications.
If desired, connect an oscilloscope to the SCOPE
output banana j jack on ae front panel.
—_
—_
NOTE: If you are going to use your Deviation Meter
for continuous monitori ing operation, you should
occasionally recheck the tuning to be sure it is peaked
on frequency.