Robotron Pty Ltd G9P 用户手册
WiNRADiO G39DDC User’s Guide
99
Of particular interest to many users will be the CPU load (excessive CPU load
may cause sluggish behaviour or freezing of the computer), and Audio
latency. Apart from DDC bandwidth, CPU load may be minimized by
reducing the Demodulator filter length (thus sacrificing selectivity) and audio
latency may be minimized by reducing the Audio buffering (while inviting the
possibility of audio drop-outs or distortion). Both these controls are available
under Options.
may cause sluggish behaviour or freezing of the computer), and Audio
latency. Apart from DDC bandwidth, CPU load may be minimized by
reducing the Demodulator filter length (thus sacrificing selectivity) and audio
latency may be minimized by reducing the Audio buffering (while inviting the
possibility of audio drop-outs or distortion). Both these controls are available
under Options.
Note that this function is also conveniently duplicated by the information
button
button
in the DDC1 spectrum scope “toolbox”.
Measuring your Excelsior’s sensitivity using your Excelsior
Using the SINAD measurement facility, you can measure the sensitivity of the
WiNRADiO Excelsior receiver very easily. All you need is a calibrated signal
generator. For example, to measure AM sensitivity, connect the signal
generator to the antenna input and turn on AM modulation (the modulation
depth is usually set to 30%, although some manufacturers prefer to quote
sensitivity figures at higher modulation depths, for example 60 or 80%). Set
the Test frequency equal to the modulating frequency (typically 1 kHz). Adjust
the IF bandwidth for the maximum SINAD. Then gradually keep reducing the
generator output level to the point when SINAD drops to 10 dB. The receiver
sensitivity is then equal to the generator level at this point.
WiNRADiO Excelsior receiver very easily. All you need is a calibrated signal
generator. For example, to measure AM sensitivity, connect the signal
generator to the antenna input and turn on AM modulation (the modulation
depth is usually set to 30%, although some manufacturers prefer to quote
sensitivity figures at higher modulation depths, for example 60 or 80%). Set
the Test frequency equal to the modulating frequency (typically 1 kHz). Adjust
the IF bandwidth for the maximum SINAD. Then gradually keep reducing the
generator output level to the point when SINAD drops to 10 dB. The receiver
sensitivity is then equal to the generator level at this point.
Measuring AM sensitivity using SINAD rather than the conventionally used
S+N/N is quite appropriate as SINAD also includes distortion, which is as
much an impediment to intelligible reception as noise, and therefore provides a
more practical result. Even though in theory using SINAD should result in the
sensitivity figures being somewhat worse than if S+N/N is used, in practice,
with a good receiver such as the Excelsior, there is no noticeable difference.
S+N/N is quite appropriate as SINAD also includes distortion, which is as
much an impediment to intelligible reception as noise, and therefore provides a
more practical result. Even though in theory using SINAD should result in the
sensitivity figures being somewhat worse than if S+N/N is used, in practice,
with a good receiver such as the Excelsior, there is no noticeable difference.
Note: When measuring sensitivity using SINAD, it is very important that the
Audio Filter is enabled and the cut-off frequencies (and for FM measurements,
also the de-emphasis) are set according to the specified test conditions. Proper
audio filtering makes a substantial difference to the SINAD results.
Audio Filter is enabled and the cut-off frequencies (and for FM measurements,
also the de-emphasis) are set according to the specified test conditions. Proper
audio filtering makes a substantial difference to the SINAD results.