eHam
eHam Forums => Software Defined Radio => Topic started by: HA3FLT on March 04, 2023, 10:34:30 AM
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Sorry for the pretentious title but... I just swept across the Receiver Test Data table at http://www.sherweng.com/table.html yesterday and found a new line that is absolutely unbelievable to me after hearing so much good things from the SunSDR2 DX:
(https://ha3flt.org/photos/Forums/SunSDR2_DX_Sherwood-001.jpg)
'a' and 'd' means:
- Measured with SSB filter
- Dynamic Range is 90dB at 100kHz spacing
This would place it between the most mediocre if not the worst receivers of todays' radios despite of its technology that usually works uncomparably better. Could it be a faulty one? Clock with very high phase noise, or else? It has a LTC2209!
Also, we have these somewhat older test results - just look at the page 8...: https://dc4ku.darc.de/SunSDR2DX_english.pdf
No way! : - )
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Not too surprising. Have a look at 2 kHz RMDR performance in the October, 2016 QST Product Review for the SunSDR2-Pro which is essentially the same core transceiver with a 15-20W PA. Based on 2 kHz dynamic range, the ancient Kenwood TS-430S outperforms.
With a DDC architecture, there's no excuse for not placing near the top with 100+ dB 2 kHz DR. That's a 30+ dB spread. It also goes to show that many folks with moderate-performing antenna systems are completely unaffected with less than 80 dB DR, a claim echoed in the past by Rob Sherwood.
Paul, W9AC
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Thank you for the answer, I did not check QST Product Reviews earlier. So, there is another source with bad numbers while the clock seemed to be fine.
It is now 2:1 (albeit from different years...), plus a lot of statisfied people on the positive side even if it means what it means. This is because the radio has a "normal", very high, top-of-the-list DR (at 2 kHz) according to DC4KU as I mentioned.
I really hope that it turns out sooner or later who made mistakes, otherwise my hardly achieved knowledge and the connection with the pure RF reality will directly convert themselves to a common black hole...
And yes, I've read about that 80 dB from Rob Sherwood earlier. :-)
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Sherwood is likely testing in an RF quiet lab setting. But for normal operation, direct sampling SDRs sometimes work better (more dynamic range and sensitivity) when connected to an antenna picking up typical wide band noise.