Finally got around to measuring the R-390A / SoftRock receiver setup I've been using for a while. A description of the system: R-390A i-f output > 15 dB attenuator > 455 kHz SoftRock > Delta 44 sound card > P4/2800 MHz/1G Ram > Delta 44 sound card > Hafler DH-110 preamplifier > Hafler P3000 amplifier.
The R-390A is run in the 16 kHz BW position and operated in manual gain control (MGC) mode with the rf gain control set to 8 - 1/2. This level was previously determined to be 'optimum' for this particular receiver. Info on this is in a previous thread:
http://amfone.net/Amforum/index.php?topic=13686.80Power SDR software was used for the test and set for 16 kHz BW, slow AGC and both standard AM and synchronous AM detectors were tested. On rare instances there was at most 1 dB difference between the two detectors - the vast majority of the time the measurements were identical.
Results are as follows:
AM audio S/N: 48 dB
AM Audio Frequency Response: in dB, referenced to 1 kHz measurement
100 Hz | 200 Hz | 400 Hz | 600 Hz | 800 Hz | 1 kHz | 2 kHz | 3 kHz | 4 kHz | 5 kHz | 6 kHz |
0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
AM Audio Distortion:Mod | 100 Hz | 200 Hz | 400 Hz | 600 Hz | 800 Hz | 1 kHz | 2 kHz |
30% | .63% | .63% | .63% | .63% | .63% | .63% | .63% |
50% | .50% | .50% | .50% | .50% | .50% | .50% | .56% |
70% | .63% | .63% | .63% | .63% | .63% | .63% | .71% |
90% | .90% | .90% | .90% | .90% | .90% | .90% | .90% |
100% | 1.3% | 1.4% | 1.6% | 1.6% | 1.6% | 1.6% | 1.6% |
Note: It's possible that the distortion numbers are even better as we're likely at the limit of the test equipment in use.
The test procedure and test results for conventional BA receivers, for comparison, can be found here:
http://www.w1vd.com/BAreceivertest.html