SDRPLay RSP1
Marcus D. Leech
the 21cm band? I have a couple of the "clones" (MSI.SDR), and they
seem somewhat "deaf" at 21cm. Like you'd need about 20dB more gain
ahead of them than even an RTL-SDR.
Hamish Barker
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Marcus D. Leech
the datasheet says it has 8 selectable front end filters. I assume there should be a selection for no filter as well, but perhaps one of the filters is still switched in?
The filter involved would be the 1000MHz HPF--basically anything above 1000MHz involves that filter.
I should probably do a more-thorough investigation into sensitivity.
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Hamish Barker
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fasleitung3
A couple of months ago someone gave me a couple of SDRs with the
request to test them. Among these was a MSI.SDR (blue housing with a
dolphin depicted on it). My experience was exactly the same, it was
deaf. I thought the unit was defective, so I did not do any deeper
testing. Now it seems that they are "deaf by design".
Cheers,
Wolfgang
fasleitung3
There is a test report which confirms that the unit is useless at 21cm:
https://saure.org/cq-nrw/2020/06/10/messungen-an-einem-msi-sdr-stick-von-gerd-dc6hl/
It is in German, but the graph and the numbers speak for themselves.
Am Mittwoch, den 27.10.2021, 21:02 -0400 schrieb Marcus D. Leech:
Dave Typinski
facing a lot of trouble from Chinesium clones and outright knock-offs (fake
products sold as genuine). A genuine SDRPlay RSP1 might fare a lot better at 21
cm than the MSI units. Caveat emptor.
--
Dave
jan Lustrup-LA3EQ
I use RSP2 for 21cm H1 work all the time! Works great, but of course you need a good LNA in front at the antenna feed.
Here is my H1 detection time lapse done with it using a Horn antenna and RAS 21cm LNA.
https://www.youtube.com/watch?v=1F9lt8_SXfc
Jan Lustrup, Norway
fasleitung3
design compared to the RSP1. And then, the clone may be different from
the original RSP1 as pointed out by Dave.
Cheers,
Wolfgang
Marcus D. Leech
> The RSP2 works fine here as well. But I think this is a different
> design compared to the RSP1. And then, the clone may be different from
> the original RSP1 as pointed out by Dave.
> Cheers,
> Wolfgang
>
>
*across the board*.
The best-case sensitivity was in the VHF range, but with a paltry -80dBm
MDS, these things are about 40dB away
from anything close to "state of the art".
In UHF, particularly at 21cm, it's about 10dB worse.
Now, I know these things are based on the original RSP1 design (NOT the
RSP1A), and I wonder if perhaps the
1A design was introduced specifically due to these problems?
Dave Typinski
by SDRPlay work fine at HF, certainly better than a -80 dBm MDS. Maybe the
genuine units too are deaf at VHF and UHF -- although that seems unlikely -- but
definitely not so across the board.
--
Dave
Marcus D. Leech
>
> More likely that the clone is a poor copy. The real RSP1 units that
> were sold by SDRPlay work fine at HF, certainly better than a -80 dBm
> MDS. Maybe the genuine units too are deaf at VHF and UHF -- although
> that seems unlikely -- but definitely not so across the board.
> --
> Dave
>
It seems that the API for SDRPlay uses the gain numbers as a *gain
reduction setting*, whereas EVERY SINGLE
OTHER SDR ON THE MARKET uses it as a positive gain setting (even
though the hardware underneath is nearly always a variable attenuator).
Since the SoapySDR wrapper for
the underlying SDRPlay hardware API doesn't really "know" this, the
gain distribution is really poor--in particular the "LNA" component
(called RFGR in the interface) takes values
between 0 and 3, and the best sensitivity is at 0. And it behaves
exactly as if the gain setting is "inverted". This is consistent with
other things I've seen about RSP-specific
apps calling it "gain reduction".
The IF gain setting "IFGR" appears to do NOTHING. So, it's not clear
whether there's much IF gain actually set by the wrapper or not. The
absolute sample values are quite
tiny, even with the "RFGR" set to 0. Given that this is likely
mostly handled by the MSi001 chip, even the "clone" should get this correct.
Lester Veenstra
Remember the MDS or Noise Figure of the receiver is of little importance.
The system noise is set by the LNA, and associated antenna system. From the LNA output, the job is to design the loss between the two units such that the receiver’s A/D is mot overloaded, and simultaniously, the receiver’s noise floor is 15 to 20 dB below the noise floor of the LNA, when received at the receiver.
Lester B Veenstra K1YCM MØYCM W8YCM 6Y6Y
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Marcus D. Leech
Remember the MDS or Noise Figure of the receiver is of little importance.
The system noise is set by the LNA, and associated antenna system. From the LNA output, the job is to design the loss between the two units such that the receiver’s A/D is mot overloaded, and simultaniously, the receiver’s noise floor is 15 to 20 dB below the noise floor of the LNA, when received at the receiver.
There are other issues I've found as well. For example if you call the "set_gain()" API call, the API balks and refuses to start streaming. I think I'm going to give up on these
for the timebeing until the API is rationalized.
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Lester Veenstra
The band pass LNA from NooElec has a lot of gain, more thgan typically usable.
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Lester Veenstra
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