User's Manual
TT21 Transponder Installation Manual 19 January 2009
00560-00 Issue AA
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5.11.3 TNC Connector
This section describes the technique for attaching the antenna cable to the supplied TNC connector.
If a low-loss cable is needed that has too large a dielectric diameter to fit the supplied connector, a
short length (up to 150mm or 6 inches) of smaller cable may be used with suitable mating connectors
to adapt to the transponder connector.
The supplied connector can be completed using a wide range of commercial crimp tools (for example
the Tyco 5-1814800-3). The die apertures for the inner pin and the outer shield should be
approximately 1.72 mm and 5.41 mm respectively.
Strip back the coax cable to the dimensions in the table, as shown in the diagram below. Slide
25 mm (1 inch) of heat shrink tubing over the cable.
Slide the outer crimp sleeve over the cable – it must go on before securing the centre contact.
Dimension Cut size
(mm)
Cut size
(inches)
A 17.5 0.69
B 7.2 0.28
C 4.8 0.19
Crimp the centre contact to the cable.
Insert the cable into the connector – the centre contact should click into place in the body, the
inner shield should be inside the body of the connector and the outer shield should be outside
the body.
Crimp the outer sleeve over the shield.
Slide heat shrink tubing forward (flush to connector) and heat to shrink the tubing.
5.12 Static Pressure Connection
The TC20 controller includes an altitude encoder which must be connected to the same source of static
pressure as the primary altimeter on the aircraft. The TC20 static pressure port provides a mounting
spigot intended for nominal 5mm or 3/16 inch inside diameter tubing. A length of 5mm EPDM rubber
tubing is included in the installation kit to facilitate connection to the aircraft static system.
Choose a point in the existing static pressure line that is as close as practical to the TC20. Cut the
static pressure line, and use the supplied T fitting to connect the altitude encoder. Take care not to
contaminate the inside of the static line when cutting or inserting the connectors.
Page 14 Trig Avionics Limited