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SDR# stops playing when using Airspy HF+

Posted: Wed Apr 25, 2018 8:35 am
by aurgathor
I have a couple of cheap SDRs (NooElec & SDR-RTL v3); and an AIRSPY HF+, and I mostly use them to listen to FM stations. With respect to performance, the AIRSPY HF+ is significantly better than the others; however, SDR# stops playback roughly once in an hour for no apparent reason when using the Airspy HF+. Same computer, same USB port , same antenna, and I'm using the supplied cable. I'm running Win 7 x64 with 24 GB of ECC RAM on a quadcore Xeon box with lots of CPU cycles to spare.

Any idea on what my be happening and how to fix it? I suspect the USB bus could be reset, but trying different ports or hubs did not make any difference. In comparison, I can leave the others running when I go to bed, and SDR# is still playing in the morning.

Re: SDR# stops playing when using Airspy HF+

Posted: Thu Apr 26, 2018 7:50 am
by JEL
This is just a guess on my part (Somebody with more knowledge hopefully comes along)

I guess there is a broader data-range sent via the USB connection when using the HF+ (Since it has a wider bit-depth)

So perhaps your USB is just 'quiet' enough to handle the 8-bit stream without issues from the 'cheap' dongles, but runs into more data-errors when using the HF+?
And perhaps SDR# stops when it receives to many error-bits?

As said; it's just a guess, but maybe the 'cheap' dongles are feeding the computer a steady slow stream of data, while the HF+ is trying to pour a heavier stream through the same hole?

I can run an 8-bit 'cheap' dongle on 10 meter USB cable, but if I try to hook up the Airspy to the same cable, SDR# goes bonkers instantly.
So data-rates being the issue is my guess :)

Re: SDR# stops playing when using Airspy HF+

Posted: Fri Apr 27, 2018 12:36 am
by rtlsdrblog
JEL's explanation sounds reasonable.

Try other USB ports on your PC too to see if it helps.

Re: SDR# stops playing when using Airspy HF+

Posted: Fri Apr 27, 2018 3:25 am
by aurgathor
I do not think data rate in itself is much of an issue in any way, though I'd definitely prefer USB 3.0 for the HF+. The cheap 8-bit SDRs usually run at 2.4 Msp/s and 16 times more data is just 38.4 Msp/s, more than enough to go through USB 2.0. But I don't think the AirSpy sends that much data anyhow since the BW in SDR# is only 768 KHz at most in the FM band.

However, with your 10 ft cable, there may be some excessive voltage drop as the AirSpy HF+ draws somewhat more current than the cheap dongles.

In addition, some USB chips are more picky about timing then others, but I do not have access to a real (HW) USB analyzer at this point in time.

In any case, since I do have a cheap "USB detector" (voltage & current measuring adapter) here are some numbers with 3 SDRs:
NooElec NESDR SMArt: 300 - 310 mA (5.10V)
RTL-SDR V3: 310 - 320 mA (5.03V)
AirSpy HF+: 370 - 390 mA (4.97V)

Lastly, I already tried several USB ports to no avail, though I have a few more hubs and power supplies that I can try.