5V Power Supply who output a "clean" 5V Power for SDR? - Page 1
Forum section: electronics / general

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 03, 2019, 02:33:48 pm
content: HiI ordered an USB Isolator who should work with my SDR. Sadly on <30Mhz my Power supply produce to much Noise. So Is there a 5V Powersupply on the European Market who filter, block,... or what ever every noise who could come via the Power Cable?Maybe some Lab Power Supply?The USB Dongle dont draw that much power so for that nothing special is necessary.The main part is no additional noise should get truth the Power cable.

author: madires
author_rank: Super Contributor
timestamp: June 03, 2019, 02:51:12 pm
content: You could try an LC filter at the output of your PSU. Start with 10-33µH and 220-470µF. Or do you have a linear PSU with transformer?

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 03, 2019, 03:02:15 pm
content: Nope nothing.

author: Gyro
author_rank: Super Contributor
timestamp: June 03, 2019, 07:18:47 pm
content: Ditch the DC-DC converter on the USB isolator. Then purchase an old transformer based wall wart with 9V output from ebay and add a 3 terminal 5V linear regulator.This is the approach I took with my 16 bit Pico ADC216 scope and USB isolator with good results.

author: Bud
author_rank: Super Contributor
timestamp: June 03, 2019, 11:06:46 pm
content: A USB rechargeable juice pack for cell phones.

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 08, 2019, 05:16:36 pm
content: So next week the Isolator should arrive here.QuoteHow should I know if the use that?

author: Gyro
author_rank: Super Contributor
timestamp: June 08, 2019, 08:34:12 pm
content: They will almost certainly be second-hand, eg. from an old modem, cordless phone etc. Weight and volume are another clue. Another one is that mains input voltage and frequency will be specified over a small range, eg. 230VAC +/- 10% 50Hz, rather than, say, 100-240V. Lastly their may be a reference to the supply being thermally fused.A couple of example UK listings:https://www.ebay.co.uk/itm/9V-Mains-AC-DC-Plug-Power-Adapter-BS0900350-For-Electric-Keyboard-tested-used/392304456528https://www.ebay.co.uk/itm/US-Robotics-SP3a-9V-1000mA-1A-AC-DC-Modem-Power-Supply-Mains-Adaptor-PSU-UK-Plug/372683226233EDIT:Actually the second one is a 9V AC output, a very definite clue!

author: ebastler
author_rank: Super Contributor
timestamp: June 10, 2019, 06:49:13 am
content: Do you actuallyknowthat the noise is coming from the power supply?Before you chase a used transformer-based power supply and tinker with adding a linear regulator, I think Bud's suggestion above is a great one, at least for testing: Use a USB power bank (rechargeable battery) to power your SDR and cofirm that the noise goes away.

author: ogden
author_rank: Super Contributor
timestamp: June 10, 2019, 07:02:35 am
content: Quote from: ebastler on June 10, 2019, 06:49:13 amUnfortunately most USB power banks are no better than phone chargers/adapters - because they have switching boost (or buck) converter inside.

author: ebastler
author_rank: Super Contributor
timestamp: June 10, 2019, 07:10:42 am
content: Quote from: ogden on June 10, 2019, 07:02:35 amDuh -- didn't think of that.The marvels of modern technology... Thanks for pointing that out!

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 10, 2019, 10:39:20 am
content: QuoteWhen I disconnect the power supply from my Laptop most noise are gone.

author: Wolfgang
author_rank: Super Contributor
timestamp: June 10, 2019, 04:29:42 pm
content: why no trivial linear PSU ? Heats your flat and keeps noise out.

author: mariush
author_rank: Super Contributor
timestamp: June 10, 2019, 04:45:27 pm
content: You could make your own linear power supplyGet a transformer that outputs 6...7.5v ACGet a bridge rectifier or 4 diodes to convert the AC voltage to DCGet a big capacitor to smooth the outputGet a linear regulator to regulate the voltage down to 5vHere's transformers that would fit your needs, just get one that can provide the current you need :long link to transformers at tme.eubridge rectifier - any bridge rectifier would do, as long as it has the current ratingcapacitor... 3300uF 16v should be enough, it's a common value used in atx power supplies so should be easy to findexample :

author: Gyro
author_rank: Super Contributor
timestamp: June 10, 2019, 05:33:13 pm
content: Yes, you can absolutely do that too. Buying a second hand transformer based wall wart off ebay just saves you the hassle of the mains side and enclosure and is probably cheaper. Just add the 7805 and capacitors of your choice.

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 12, 2019, 10:06:42 am
content: HiToday I received the Isolator. Sure I dont have a Power Supply yet.Here 2 Screenshots.1) with the Isolator:https://www.delock.de/produkte/S_62982/merkmale.html2) with the USB Hub:https://www.delock.de/produkte/678_extern/63311/merkmale.htmlBoth are powered by the Latop (who is a Power Plug connected)

author: The Soulman
author_rank: Super Contributor
timestamp: June 12, 2019, 11:41:06 am
content: Quote from: Lord of nothing on June 10, 2019, 10:39:20 amDoes your laptop have a grounded plug? if so, is it connected to a properly grounded outlet?

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 12, 2019, 12:53:24 pm
content: YesAnd I guess Yes.

author: madires
author_rank: Super Contributor
timestamp: June 12, 2019, 02:45:23 pm
content: Have you already tried to power your SDR via a different wall outlet (or different phase, or different room)? I had a similar issue with a SW receiver which was resolved by moving the receiver's linear PSU to another socket. I've tried a cap between the PSU's negative output and PE, also a direct connection to PE. Slight changes, but still no real improvement. My guess is that the noise was created by the PE current from computer and monitor SMPSUs (Y caps) powered via the same socket. Moving the receiver's PSU to another socket, not daisy-chained with the former one, without any SMPSUs worked wonders in my case. Solving noise problems can be quite time consuming, but also very educational.