I have an Airspy S2 and
an SDRPay RSPdx and they both play well with SDRC.
Performance wise there are
clear differences and I find the RSPdx a bit deaf compared to
the S2, especially on 6 meters.
When I compare the raw
number of decodes on FT8 per 15 sec sequence, or the same
decodes per seq using MSK144, the S2 is quite a bit more
sensitive. I am driving the SDRs from my Kenwood TS-590sg
antenna output port, which loses 3 dB of signal, but that has
not proven to be a factor.
If you look at the specs of
the RSPdx, it has a very high noise figure on HF especially. I
found at my rural qth, a wideband preamp made a big
difference. With the preamp, the performance of the RSPdx is
equal to or better than my TS-590sg on all HF bands.
Again, the measure in number
of decodes/sequence on FT8. I pay little or no attention to
the raw SNRs, as they can be quite misleading due to AGC
The preamp has caused no
overload issues of any kind. I don't use the RSPdx for BC band
reception as a rule, but I have no overload or intermod issues
from either FM or BC stations to my work on ham radio bands,
and very good antennas.
For normal HF work, the
RSPdx is quite good, clearly better than the FunCube Pro+ on
HF (the FC+ is excellent on satellite work with an appropriate
On 6 meters, even with the
preamp, the RSPdx is not in the same league as the Airspy S2.
So, if your interests are
HF, the RSPdx is fine. If VHF, not so much.