Tait TB8100, Руководство пользователя

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110 Part F: Configuring Channels
© Tait Electronics Limited December 2007
Max Tx deviation
has subaudible
signalling
Specifies whether subaudible signalling adds to the actual maximum transmit
deviation or is included in it. It is important to select the correct option to
ensure that you comply with the relevant standards.
Talk through
repeater gain
Specifies the gain in dB that will be applied to received audio that is fed into
the transmitter. See
“Repeater Options” on page 117 .
Automatic gain
control (AGC)
Specifies whether automatic gain control is applied by UHF receivers (H, K,
and L bands) to received audio. AGC is applied at the RF stage. It enhances the
ability to handle high signal levels and to protect against receiver
intermodulation. However, when signal levels are high, the minimum
sensitivity may be degraded. The AGC setting has no effect on VHF receivers.
AGC is normally enabled, but Tait recommends disabling it when:
Q
The anticipated receive signal strength is < -107 dBm (1 microvolt) and
strong interfering signals (> -30 dBm (7000 microvolts)) are anticipated at
the receiver input.
Q
TIA/EIA or AS-4295 RF performance testing is being carried out.
Transmitter Power Output
In the Add or Edit Channel Profile dialog, General tab, the Transmitter
power output area specifies the output power of the transmitter.
The output power is specified separately for mains-powered and for
battery-powered transmissions. You can also specify a third output power, for
selection by Task Manager action. The boxes alongside display the equivalent
power in dBm.
If you specify 100 W and the PA is rated at 50 W, it will run at 50 W. There
is therefore no need to alter this value if you temporarily substitute an amplifier
with lower power, for example, if there is a fault and you don’t have a fully
powered module on hand.
Option Description
Superimposed The subaudible (10–300 Hz band) deviation does not alter the audio (0.3–3.4 kHz
band) deviation transmit levels. The audio path signal thus uses all the allocated
channel deviation and subaudible signals are summed on top of the audio signal.
It is therefore possible to transmit levels that exceed the channel limits.
For example, if a wide band channel is configured with a subaudible deviation
level of 10% and a line input level of -10 dBm, its transmit deviation (with the
subaudible signal filtered out) will be 3.0 kHz, when the line audio input is
-10 dBm.
Included The subaudible deviation reduces the level of the audio deviation out of the
limiter by the amount of subaudible deviation selected. This ensures that the
radio will never transmit levels that exceed the maximum transmit deviation
when using subaudible signalling.
For example, if a wide band channel is configured with a subaudible deviation
level of 10% and a line input level of -10 dBm, its transmit deviation (with the
subaudible signal filtered out) will be 2.5 kHz, when the line audio input is
-10 dBm. The maximum in-limiting deviation will be 4.5 kHz, within the 5 kHz
channel limit.