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Airspy Discovery

Simon Brown
 

So,

 

New owners – first impressions?

 

  • Like it
  • Hate it
  • Buying another
  • Taking dog for a walk

 

Simon Brown, G4ELI

https://www.sdr-radio.com

 

Guy Atkins
 

Hi Simon,

The Discovery arrived here at my QTH near Seattle, USA this morning, and of course a brief test was in order. My DXing interests are foreign stations on MW, so I wanted to see how the Discovery performs close in frequency to strong local stations.

I gave the Discovery a brief and unscientific test at local noon. I was using both the FDM-DUOr and Discovery with Studio 1 software. I don't have an antenna switch on my desk at the moment so I quickly swapped the antenna manually between radios. I'm also not currently up for separate instances of Studio 1 (although it does that fine), so I restarted the software between each quick session, choosing the appropriate EXTIO file. This means there was some time for the weak signals to potentially fade between the quick A-B sessions. The medium wave band at midday is fairly stable though.
 
I immediately went to a couple of weak station frequencies that surround my local flamethrower (1 kW at 1.5 mi.) on 1450 kHz. The level of 1450 is about -35dBm on my ALA1530LNP Imperium. These stations on 1430 and 1460 are borderline-audible most of the day but with best reception in LSB or USB. Today I noticed that only 1430 was audible for testing, and it was bothered by splatter from 1450 as usual.
 
Both radios were run in the 768 kHz sampling rate, because that's the maximum out-of-the-box setting for the Discovery. Same mode, same bandwidths, same AGC, etc. were used of course. The FDM-DUOr demodulated 1430, providing weak but clear audio with some interference evident from the 1450 station. No attenuation was needed or adjustment of any gain setting. 
 
The Discovery nearly equalled the DUOr on this station (only a whisker of a difference, if any), although getting the same results was a bit "fiddly". I couldn't decide if using the automatic gain of the Discovery is best, or if using the manual gain setting is better. I'm leaning toward the auto gain feature...although it is hard to ignore the 20-30 dB difference in noise floor when using the auto setting. (The specific handful of manual gain settings of the Discovery which avoided overload resulted in a noise floor roughly equal to the FDM-DUOr's; but the auto gain feature raises the noise floor significantly along with the relative signal levels.) If I judged by ear only, and also looking at the S/N of 1430 kHz on Studio 1's I.F. display, then auto gain was better--with near-equal results to the FDM-DUOr. The DUOr was ever so slightly ahead of the Discovery in this difficult close-in strong signal test. With more experience with the Discovery I expect I'll be able to extract even better results.

Note that I've calibrated the level meter for the DUOr in HDSDR using an external signal source, but I've not done any calibration in Studio 1.
 
I tuned a few other weak daytime signals on MW and found it impossible to find any differences between receivers. Bravo, AirSpy! Considering the price difference this is an eye-opening performance turned in by the HF+ Discovery.  I look forward to night time tests, and serious coastal DXpedition tests in a few weeks. This will be the proof of the Discovery's abilities for me, seeking weak trans-Pacific medium wave signals with large directional antennas.

73, Guy