Instruction manual

ACU-1000 Operations Manual
Interoperability Now 4-11
• Click “Apply” to save the setting.
• Is equalization or frequency shaping required? See Section 2.17.2.15. [Note: If the
interface is using speaker audio from the radio, the level will vary depending on the
radio’s volume control setting. Set the RX level in the DSP to 0 dBm, and then vary the
radio volume level until the proper Signal LED indication is achieved. Note the setting,
and keep the volume control at this setting.]
Set TX Level Procedure
The proper TX level is required to fully modulate the transmitter, but not over modulate it.
Most radios have an audio limiter prior to the transmitter to prevent over modulation. Even
with the limiter, some radios will still over modulate and some even shut off the TX signal
when the input is too high. When the level is set too low the audio of the radio receiving the
signal will be lower than normal, requiring that its volume control be turned up to an abnormal
position. When the audio is too hot, the audio will sound squashed, or forced, and if the radio
does not have a TX audio limiter, the audio will sound distorted and over-modulated.
• Cross-connect the HSP Module to the DSP Module being adjusted, and use the HSP
Handset to key the radio while speaking at a normal volume level.
• Monitor to the TX audio of the interfaced radio on a receiver set to the radio’s TX
frequency.
• The quickest way to set the TX audio level is to use the ACU Controller to set the DSP
Module’s TX level to its lowest setting. Increase the TX level until the audio in the
monitoring radio stops increasing in level. This is the threshold point where the limiter
is preventing the TX level from going any higher. Leave the DSP Module’s TX level at
this threshold value.
• You may also follow the radio’s recommended TX input audio setting procedure.
• Click “Apply” to save the TX Level setting.
4.8.1.1 Telephone Connection Audio Levels
If telephone audio levels do not seem to be optimum, perform the PSTN-2 Simplified Setup
Procedure carefully as described in Section 2.17.3.15. Verify that the telephone line losses and
impedance are within standard limits. If problems still persist, please contact the Raytheon
factory for assistance.
4.8.2 Noisy Received Signals
Certain types of radios such as HF, and AM typically contain a lot of noise in the demodulated
signal. Even FM radios operating near their sensitivity limit will contain noise in the signal.
The DSP-2 includes a noise reduction feature that should be considered if a particular channel
is inherently noisy on a continuous basis.
The DSP-2 uses time domain mode noise reduction, designed to peak up any correlated
information (such as speech), in the audio passband. It reduces noise by forming dynamic
bandpass filters around correlated information, thus automatically reducing the bandwidth to