Tait TB8100 User Manual page 130

Extended bypass
Line level
120 Part F: Configuring Channels
If the High pass filter check box is cleared, any DC content present on the input
will also offset the Tx carrier frequency. Even with no input, a small fixed
frequency carrier offset may be noticed. Clearing the check box will mean that
the frequency stability of your system is dependant on the input DC signal
stability, not the internal or external frequency reference accuracy.
When the Bypass check boxes are enabled on both the transmit and the receive
paths, Extended bypass check boxes appear. Extended bypass adds an equaliser
that amplifies higher frequencies to extend the available audio frequencies on
the unbalanced line, providing up to 6 kHz (receive path) or 5.5 kHz (transmit
path). Enabling one Extended bypass check box automatically enables the
other; you cannot configure extended bypass separately for the transmit and
receive paths. Enabling extended bypass makes the balanced line and internal
talk-through repeater connections unavailable; their screen display is therefore
disabled.
The high pass filter is also available for extended bypass.
Extended bypass is necessary for applications such as 9600 baud data in the
GMSK format using external modems. See TN-1114-AN for more details.
The Line level boxes on the transmit path define the level of the line input that
the base station expects. The line level you select affects the gain across the
transmit path.
When the base station receives a line input at the level you select, it transmits
at 60% of the maximum transmit deviation. For channels using the default
profile, the maximum transmit deviation is determined by the channel spacing
(see "Channel Spacing" on page
defined by the parameter Max Tx deviation (see
page 109).
Channel spacing
12.5 kHz Narrow Band
20 kHz Mid Band
25 kHz Wide Band
Line levels are expressed as dBm for the balanced line input and Vpp (volts
peak-to-peak) for the unbalanced line input.
Tip: To determine the expected line level, set up your system and
use a Service Kit diagnostic test to measure the level. See
"Measuring the Audio Input Level" on page
138). For channels using custom profiles, it is
"Max Tx deviation" on
Equivalent Tx max
deviation (Hz)
2500
4000
5000
© Tait Electronics Limited December 2007
60% of Tx max
deviation (Hz)
1500
2400
3000
175.