[Skimmertalk] RedPitaya 125-10 vs 125-14

[Dave Pascoe]

Forwarded to me by N9VV:

Re: Testing SDR receivers. Perhaps we can glean some information from the
extensive work done by Adam VA7OJ/AB4OJ. Adam has proposed his new "NPR"
(Noise Power Radio) SDR test and it has been endorsed by Rob Sherwood.
Here is a link to Adam's in-depth website:
<URL:http://www.ab4oj.com/test/main.html
>
<URL:http://www.ab4oj.com/test/docs/npr_test.pdf
>
Adam and Rob have proposed this new measurement to the ARRL for their Lab
Reviews of equipment in QST. The ARRL is considering adopting NPR.

thanks for allowing me to insert this information into the discussion,
Happy Thanksgiving,
73 de Ken N9VV


On Thu, Nov 23, 2017 at 10:13 AM, Ken N9VV <n9vv at wowway.com> wrote:

> Hi Dave, would you please take a look at this info and pass it along to
> the Skimmer group if you think it is relevant.
>
> Re: Testing SDR receivers. Perhaps we can glean some information from the
> extensive work done by Adam VA7OJ/AB4OJ. Adam has proposed his new "NPR"
> (Noise Power Radio) SDR test and it has been endorsed by Rob Sherwood.
> Here is a link to Adam's in-depth website:
> <URL:http://www.ab4oj.com/test/main.html
> >
> <URL:http://www.ab4oj.com/test/docs/npr_test.pdf
> >
> Adam and Rob have proposed this new measurement to the ARRL for their Lab
> Reviews of equipment in QST. The ARRL is considering adopting NPR.
>
> thanks for allowing me to insert this information into the discussion,
> Happy Thanksgiving,
> 73 de Ken N9VV
>
>
> On 11/23/2017 8:57 AM, Dave Pascoe wrote:
>
>> True, Paul.
>>
>> I have the instrumentation to do the MDS and blocking signal measurements,
>> but the real question is...what other measurements matter and how to
>> properly instrument them? Some of the classic measurements performed on
>> analog (traditional superhet) receivers do not translate well to SDR
>> receivers - 2-tone IMD tests, for example. The cause of effect of receive
>> IMD in SDRs is different. Of course we can compare two SDRs under the same
>> test conditions...but do we ever see those test conditions in the real
>> world? If no, then what do the tests indicate for us?
>>
>> The performance of any of these radios in a Skimmer Server environment is
>> largely a function of A/D and D/A performance. Assuming no strong (large
>> signal) signals are present in the receiver environment, then noise floor
>> at the lower end plays a large role in the apparent performance. There are
>> other variables that can play a role, like LO stability and IQ imbalance.
>> It is difficult to measure some of those effects.
>>
>> So it begs the question...what are we testing for and under what test
>> conditions? Before we talk about measurements we need to define the
>> measurement conditions and what we expect to get out of the measurements,
>> and how to properly perform them.
>>
>> Dave
>>
>>
>>
>> On Thu, Nov 23, 2017 at 9:34 AM, Paul <gw8izr at gmail.com> wrote:
>>
>> Yes as I said before, plenty comparison but no measurement, as long as you
>>> are happy and it works in your rf environment that’s good.
>>>
>>> 73 de Paul GW8IZR
>>>
>>>
>>>
>>> On 23 Nov 2017, at 14:23, Dave Pascoe <davekm3t at gmail.com> wrote:
>>>
>>> I don't have a 10-bit Red Pitaya but I do have several QS1R's and a Red
>>> Pitaya 14-bit SDR. I have compared a many days of results between the
>>> QS1R
>>> on 80-10m and a Red Pitaya on 80-10m, both fed from the same antenna(s)
>>> through a known equal power divider network. These comparisons were also
>>> done through a few contests by now. I have found the Red Pitaya to be
>>> every
>>> bit as good as the QS1R (produces same volume of spots, +/- a very small
>>> %
>>> variance) and would not hesitate to recommend it as a replacement.
>>>
>>> Whether a 10-bit vs. 14-bit Red Pitaya make sense for a given location,
>>> the first thing I would look at is the external noise situation at that
>>> QTH. If you are external noise limited then you may not see much of a
>>> difference.  :-)
>>>
>>> An i7-class PC can run two instances of CW Skimmer on two separate Red
>>> Pitaya SDRs without breaking a sweat. But adding RTTY in there will cause
>>> the CPU to be saturated during RTTY contests - but should be OK in
>>> non-contest times.
>>>
>>> Hope this helps.
>>>
>>> 73,
>>> Dave KM3T
>>>
>>>
>>> On Thu, Nov 23, 2017 at 7:08 AM, Paul <gw8izr at gmail.com> wrote:
>>>
>>> Hello Stefan,
>>>>
>>>> I would also very interested to see noise performance of the Pitaya
>>>> board, I’m not convinced that this is a receiver intended for crowded
>>>> bands. Whilst there may be some rudimentary comparison made between the
>>>> receivers, that hasn’t been suitable in depth measurement (not that I’ve
>>>> seen anyway)
>>>>
>>>> Personally I don’t see it as being a suitable replacement for QS1r or
>>>> Perseus etc
>>>>
>>>> 73 de Paul GW8IZR
>>>>
>>>>
>>>>
>>>> On 23 Nov 2017, at 10:54, Stefan von Baltz, DL1IAO <
>>>>>
>>>> dl1iao at contesting.com> wrote:
>>>>
>>>>>
>>>>> Hello all,
>>>>>
>>>>> In theory the 125-14 with its 14 bit ADC should be superior to detect
>>>>>
>>>> weak signals on a busy band due to its higher dynamic range. Has anyone
>>>> actually compared the two different Pitayas? Which Pitaya are you using?
>>>> JF2IWL has shown that a 125-10 compares well to a QS1R and S9-C.
>>>>
>>>>>
>>>>> I see that you can run CwSkimmer and RttySkimmer with one Pitaya and
>>>>>
>>>> one PC. But does anyone run 2 Pitayas on one PC with 2 instances of
>>>> CwSkimmer or even 2 instances each of CwSkimmer and RttySkimmer? This
>>>> would
>>>> require a powerful PC, though.
>>>>
>>>>>
>>>>> Thanks in advance!
>>>>>
>>>>> 73,
>>>>>
>>>>> Stefan DL1IAO, SA3CWW/SM9A
>>>>>
>>>>>
>>>>> --
>>>>> Stefan v. Baltz
>>>>> DL1IAO at contesting.com
>>>>> http://www.dl1iao.com
>>>>>
>>>>> Sent from my iPhone
>>>>>
>>>>> _______________________________________________
>>>>> Skimmertalk mailing list
>>>>> Skimmertalk at contesting.com
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>>>>>
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>>>
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>>
> --
>  ¯\_(ツ)_/¯
>
>