M850-00
T858/859 General Information
D1.7
Copyright TEL 31/09/98
1.1 Introduction
The T858 and T859 are FM base station power amplifiers designed for single or mul-
tichannel operation in the 400 to 520MHz frequency range. The output power capabili-
ties are as follows:
T858 - 10 to 60W
T859 - 20 to 110W.
The PA comprises a broad band, three stage drive amplifier whose output is split to
drive two separate output stages. The outputs from these final stages are then recom-
bined and filtered before being fed to the output socket. This type of balanced output
stage offers two advantages over single ended types:
• improved intermodulation performance in the presence of high signal levels
from adjacent transmitters;
• enhanced reliability: if one of the two output stages fails, the transmitter can
still produce one quarter of its rated power.
VSWR and thermal protection are incorporated into the basic design, while monitoring
and alarm signals are available for both forward and reverse power. The output power
is adjustable from the front panel.
The main PCB is mounted directly on a die-cast chassis/heatsink. Extensive use is
made of the latest surface mount technology.
Forced air cooling for the heatsink is provided on the T859 by a fan, which is activated
whenever the transmitter is keyed. Thermal sensors will also activate the fan automati-
cally if the internal temperature reaches an unacceptable level.
The T858 has a width of 60mm and occupies a single space in a Tait rack frame, which
has the ability to accommodate up to seven standard modules. The T859 has a width of
120mm and occupies a double space.
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