1 . These units are designed to enable the Racal RA . 1 7
and RA. 117 Receivers, or other suitable communication
receivers having a 100 kc/s i.f. output, to be used for the
reception of independent sideband and single sideband
signals, with the carrier 0 to -26 dB relative to sideband
power. Provision is made for the unit to be locked to an
external high stability frequency source for suppressed
carrier applications. It can also be used for the single
sideband reception of double sideband transmissions with the
advantages of reducing the effects of selective fading and,
by the choice of either sideband, avoiding adjacent channel
interference in most cases.
2. A very accurate crystal - controlled a.f.c. system is
used to compensate for drift in the adaptor, receiver or
distant transmitter; the tuning
frequency is held to within ±3 c/s over a drift range of ±1
kc/s. This provides the tuning stability necessary for
satisfactory and reliable independent or single sideband
3. A carrier derived a. g. c. output (d. c.) is available
from the adaptor for the purpose of controlling the receiver
gain, both to counteract fading
and to keep the input level to the adaptor within the
optimum working range.
4. The RA. 98A and B adaptors are self-contained and are
designed to operate from the 100 Kc/s i.f. output of the
receiver. The only differences between
the A and B models are in the types of coaxial connectors
and phone jacks used and the power switch operation.
5. The adaptor is designed for rack mounting or for fitting
in a suitable cabinet above the RA. 17 or RA. 117 receiver.
All electrical connections with the
exception of the headphones are made at the rear of the unit.
6. A dust cover is fitted which provides adequate
ventilation and at the same time ensures ample protection
from dust and dirt.