A.W. Communication Systems DRC1 Configuration Handbook - page 10
From the installation menu select trim line input
Adjust the line input for a reading of –20dBm on the meter
Store this value (press menu)
Increase the line input level to –10dBm and check output is also –10dBm
Increase the input level to 0dBm and check output remains at –10dBm +2dBm-0
Transfer the meter to the line output port and set input level to –20dBm
Select trim output level and set level on meter for –20dBm, store this value.
Increase line input level to 0dBm and check output level remains at –10dBm +2dBm-0.
Theory
Limiting within the DRC1 amplifier chain is set to start at around –10dBm. The initial setting
process at –20dBm is undertaken at a level which will be well outside of the limiting range.
By setting the initial level on the auxiliary ports, the input gains are set to a known value, and,
out of limiting. The output is then set against this known value.
Method 2.
From the installation menu set keying to 2970Hz, store this value (press menu).
From the installation menu set talk through to local
Connect the selective measuring set to the line output pins on the line port.
Set the measuring set to 2970Hz and a bandwidth of not more than 100Hz
From the installation menu select trim line output level
Whilst pressing the PTT key adjust the line output level for –28dBm as seen on the selective
measuring set. Store this value (press menu).
Place an audio oscillator onto the line input pins of the line port
Set the oscillator for 1Khz –20dBm
Set the selective measuring set to 1Khz 100Hz band width.
Press talk through (led on)
From the installation menu select trim line input
Adjust the trim until the output is –20dBm. Store value (press menu).
Increase the line input level from the oscillator by 10dB
Check that a corresponding increase is seen on the selective measuring set.
Increase the line input to 0dBm, and check output is –10dBm +2dBm-0.
Theory. The key tone level has a fixed ratio to peak level of –18dB or –28dBm. By setting
the line output level whilst measuring the key tone the line output amplifiers are calibrated
and the gain values stored. Setting the input to –10dBm and adjusting the input amps for –
10dBm as seen on the output calibrates the internal system gain to 0dB. The base station
installation should be adjusted for nominal –10dBm levels, however using the DRC-1 line
trim facility permits local adjustments of the full path loop gain.