Good Evening All,
I am testing a two switch QSD circuit for use in the v5.0 SoftRock.
The switches in the QSD are each on for 50% of the clock cycle and
staggered by 90 degrees. All other circuits in this test version of
the SoftRock are the same as the v4.0 SoftRock.
In the present v4.0 SoftRock there are four switches with each
switch on for 25% of the clock cycle. Two switches, staggered by 180
degrees, connect alternate ends of transformer T1,(+/-RF), to the I-
signal integrating cap. In the same maner but 90 degrees offset from
the I-clocking, two switches provide the input to the Q-signal
integrating cap. Typical performance with the v4.0 is a noise
baseline of about -139dBm when PowerSDR is calibrated for -73dBm at
50uV RMS.
With this two switch QSD SoftRock I am seeing a 3dB decrease in
signal strength compared to a v4.0 when checking with a -73dBm
source. The noise baseline comes up to -135dBm when PowerSDR is
calibrated with the two switch QSD to -73dBm. Some loss of
sensitivity but still a MDS on the order of -131dBm.
Still working on the schematic for the v5.0 SoftRock, but hope to
have it ready to post soon.
73,
Tony KB9YIG
