USB 3.0 hub SDR interference

[ExploitedSanity]

Hello all. Because I KNEW that I would want more than one dongle, I had purchased a cheap plastic powered 10-port usb 3.0 hub from Amazon. It puts off a lot of interference pulses. Found this out by unplugging things one at a time. I'm hoping that there's a way to decrease or eliminate the interference with one of those ferrite cores I hear about? If so, where would the best placement be? I was looking at the little 20pc kits. As cheap as they are, would it do me good just to toss cores on everything?

 

[RaleighGuy]

I'm hoping that there's a way to decrease or eliminate the interference with one of those ferrite cores I hear about? If so, where would the best placement be? I was looking at the little 20pc kits. As cheap as they are, would it do me good just to toss cores on everything?

Don't go cheap, buy a good USB Powered Hub. There isn't a price difference because people want to make more money, it is because you get what you pay for, cheap vs quality.

 

[slicerwizard]

Ferrite cores might do a little bit, but this thing runs off a wall wart, yes? It's got a noisy switching supply in it with no snubber circuitry and everything has cheap plastic casings, so the noise radiates right through the case. Might even be noisy components in the hub itself. Since it's from Amazon, should be easy to return if you haven't waited too long. You might have better luck with a good brand name (Anker, Belkin, ...), just don't buy anything that you can't return.

 

[Ubbe]

USB cables can produce a lot of RF interference. Some of the cables already have a ferrit core to reduce RFI. Interference are radio waves and one of them could be at the frequency you are trying to receive. As it is a wave it will have a maximum voltage and maximum impedance at the waves peak and it's there you would like to use a suppressing ferrit core that works as a low impedance trap.

As it will be difficult to know where that wave maximum will be on the cable you can use several ferrit cores together and one of them will hopefully be at the correct position. It's each half wave that have a maximum so at 800MHz you'll need to cover 18cm or 7 inches. Double that at half the frequency 400MHz. If you have a ferrit ring you can wind the cable several turns inside it to cover a larger length of the cable.

If you only have one ferrit core you can listen to the interference and then move the ferrit core on the cable until you get maximum suppression. But that will only be good at one frequency range. Also try to use cables that are thicker and more stiff as it probably indicates that it is well shielded.

/Ubbe

 

[ExploitedSanity]

Thanks y'all. I think most of the noticeable interference IS in both the 800 and 400 ranges. I just ordered one of the ferrite packs for now We'll see if it helps. Next, a hub replacement for Christmas is in the future if needed. Thanks for the tips.

 

[jeepsandradios]

I use Startech USB Powered hubs and have had decent performance with them. Work well for my SDR stack.

StarTech.com 7 Port USB 3.0 Hub (5 Gbps) - Metal Enclosure - Desktop or Wall Mountable - Rugged & industrial Powered USB Expander and Splitter Hub (ST7300U3M)​

 

[slicerwizard]

I think most of the noticeable interference IS in both the 800 and 400 ranges.

Switching supplies often run around 150 kHz up to maybe a few MHz, but the harmonics go much higher. Your ability to detect them may be affected by your RX antenna and where it's resonant. Also the lengths of the wires that the noise is using as TX antennas (i.e. where they're resonant).