Hi All,
The latest QST, Dec 08, has a test of the Perseus HF receiver.
The dynamic range data suggests 1 dB compression for a signal
99 dB above MDS which evaluates to -27 dBm. The mechanism is
that sideband noise from the test oscillator activates the AGC
and reduces the gain. (With AGC off there is no gain compression
until above A/D saturation.) perseus.exe has a very low
threshold for the AGC by default. I do not know how to
change it (if possible.)
I tried to do the measurement with Winrad where I can set the
AGC threshold. (ARRL Lab should have no problem to use Winrad.
Using Linrad would require far more time....)
Things behave as expected with one exception:
When I switch off the AGC and increase the signal level, there is
a point where Winrad overflows. The program crashes and the exit
button does not work. I have to use Ctrl Alt Del to be able to
kill Winrad. The crasch happens at S9+20 dB when RF gain ("Lev")
is set to maximum and it does not happen at all when RF gain is
set to minimum. The bug is 100% reproducible so it should be easy to
find:-)
73
Leif / SM5BSZ
