Section 1
I GENERAL INFORMATION
1.1 FEATURES
The TF 144H series of signal gener-
ators give c.w, and a. m. outputs suitable
for the standard measurements and tests on
equipment operating in the m. f. , h. f. , and
lower v. h. f. bands. Their good frequency
stability and high-discrimination tuning are
of particular advantage in testing narrow-
band communication receivers.
Each generator covers 10 kc/s to 72
Mc/ s in twelve ranges. Eight of these ran-
ges follow a straight-line frequency law and
have a frequency cover of 2:1; the remain-
ing four have a slightly greater range and
one of them covers the medium-wave broad-
cast band.
A large effective scale length
is provided on the main tuning dial whichhas
separate hand-calibrated scales for each
range. Its discrimination is such that a 2%
frequency change on any band occupies more
than a quarter of an inch of scale length.
Frequency accuracy is ±1%, but for greater
accuracy there is a built-in crystal calibrator
which gives at least 90 crystal check points
throughout the twelve ranges.
An 8:1 reduction drive from the main
tuning control enables easy and precise adj-
ustment to be made, and a linear logging
scale with 100 divisions attached to the main
tuning control facilitates interpolation be-
tween any of the main-scale divisions.
In
addition to the logging scale, a fine tuning
control is provided which is operative above
80 kc/ s and enables incremental frequency
adjustments to be made, with complete
freedom from backlash, up to ±0. 5% of the
frequency in use.
Modulation can be applied from an inter -
nal 400-c/ s to 1000-c/ s oscillator or from
an external source. In both cases, depth is
variable up to 80% over most of the frequency
range.
There are two r.f. signal outlets. One
supplies an output e.m.f. switchable between
2 and
2.
75 volts (monitored by the meter) at
very low impedance while the other supplies
a variable e.m.f. between 2 µV and 2 volts via
coarse and fine 50-ohm attenuators; the out-
put range may be extended down to 0.2 µV by
using the 20-dB Attenuator Pad accessory.
A system of automatic level control keeps
the carrier level constant throughout wide
frequency changes.
Designed for operation from either a. c.
mains or battery supplies the instrument is
available in forms suitable for bench or
rack mounting, as detailed below.
1.2 STANDARD AND SERVICES VERSIONS
TF 144H/4 and TF 144H/4R are the
standard bench- and rack-mounting models.
The versions with suffix 'S' are Services
types which are distinguished from the stan-
dard models by a sealed round meter, a
Plessey Mk. IV mains supply plug, and acc-
essories supplied.
Standard Models
TF 144H/4 : Bench mounting
TF 144H/4R : Rack mounting
Services Models
TF 144H/4S : Bench mounting.
No acces-
sories. Joint-Service Ref. No.
CT 452A.
TF 144H/6S : Bench mounting. With acces-
sories. Ref. No. CT 452A Set.
The accessories supplied and available
are described in Section 1.4.
144H/II (1)
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