USB -> Glasfiber for the best isolation? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 30, 2018, 09:48:44 pm
content: HiI search for an 50m SC/SC Cable and found from an Company an USB -> Glasfiber Abapter:https://www.lindy.de/USB-3-0-LWL-Fibre-Optic-Extender-200m.htm?websale8=ld0101.ld011101&pi=42707&ci=225No. 42707and: No. 42683, No. 42701So can the help me to get the noise floor down on the SDR Stuff? Sure the require an Power Supply on the other side but the Pc, Laptop, Server (!!!) in my Case can be far away (in my case 60m - 50m Cable)And I could connect it directly to my Physical Server and Pipe the Data into an Virtual Pc.EDIT: USB 2.0 LWL:https://www.lindy.de/USB-2-0-MM-LWL-Fibre-Optic-Extender-200m.htm?websale8=ld0101.ld011101&pi=42702&ci=50EDIT 2:I found other! Even with USB 2.0 and 4 Ports. Sure the say EOL maybe I got some cheaper.I need at the moment:2x for SDR*2x for SDR**1x for SDR***1x for the USB Sound Modem to the CB Radio.

author: CopperCone
author_rank: Super Contributor
timestamp: July 01, 2018, 01:15:18 am
content: I got a corning brand USB fiber isolator but the problem is that it has power wires. The ends are tiny. You would need to cut open both ends, cut the power wires, or possibly open up the whole wire length wise to remove the wire, which may act as a weak coupler, like gutting a fish bone, then power the other end off batteries I guess, I think, unless the fucking thing uses lasers to power the other side? I mean it should still be better but it would be better if it was totally isolated like yours. I did not know they sold that.It's laying around, i got side tracked before investigating it too much.You might also want a USB filter (digikey sells em) to cut down power supply noise / tame a insufficently designed laser to digital converter they may have made haphazardly. I believe they will bandlimit the USB signal to reasonable square wave edges.Also Can you post a picture of the webpage, it requires a registration.I was not that concerned though because a SDR kind of sucks with noise floor, unless you have like high end stuff. I figured it would be better then nothing, and that most of the nasty noise came from the digital side.Using pure fiber link would be real nice though, but the stuff you got in mind real looks pricey.I think with a SDR though, a decent portion of noise might come from in-band noise that can get through the signal chain in reverse emanating from the processor/FPGA. I'm not sure how much you can do. May be possible to mod a SDR physically by putting an isolator between the ADC and the FPGA/MCU, but it would have to be a very good isolator, and the ones that use RF would probably be out, so you would need some kind of fast optical ones driven hard, and I don't know what the additional jitter introduced by the buffers/etc would do to the data and digital algorithms. I figured the timing margins might be really tight with a SDR but I really don't know.

author: xaxaxa
author_rank: Regular Contributor
timestamp: July 01, 2018, 04:01:58 am
content: USB is the least of your concerns when it comes to interference in a sdr receiver. Any decent usb sdr will have ferrite beads and ceramic caps on the power line that will easily get rid of anything >1MHz; spurs are generated by the sdr itself. If you are seeing LF/baseband interference then a big 470uF cap on the usb 5V bus should fix it (note: also makes the device technically noncompliant with usb specifications).Noise is another matter entirely and depends only on your frontend LNA; you can arbitrarily lower the noise figure by adding a higher gain LNA, but this also fucks up your linearity because the sdr now sees stronger signals and interferers. If you want good sensitivity you need an sdr that has simultaneous low noise figure and high IIP3 (input third order intercept point). Most manufacturers quote noise figure at max gain setting while IIP3 at lowest gain settingwhich is completely misleading and tells you nothing of its real performance. The limesdr mini is currently the only decent and reasonably priced sdr which has good IIP3 at max gain (4dBm IIP3 and 3.5dB noise figure simultaneously). rtl-sdr has fairly bad linearity but it's a nice sdr given its price. Anything else don't bother.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 01, 2018, 08:50:00 am
content: QuoteThe "Lindy" USB 2.0 MM LWL/Fibre Optic Extender 200m (also the USB 3.0 Version) cost me as an Dealer 340 € exclude Tax. I get an Discount when I buy +3 (327 €).So search on Lindy.de for:No. 42702No. 42707The good think is the are 100% isolated between both side. Sure the have to use an Power Supply.The Point for me is I can have the Dongle near the Antenna and the Data can be procecced by the (Virtual) Server in my Basement where its cold and nobdy care about the noise. Thankfully the most Software is that slim and good programmed to run 24/7 over month.@CopperConeSo does it work in your case (even with the Noisy Power from the Pc)?@xaxaxaFor me the big Plus is I can connect the SDR with my Server and have a) the best Signal because the SDR is near the Antenna and b) the Signal gets Processed by the Server who runs currently with 20% load.(Behind the Server is an huge UPS and other Stuff).EDIT: I also will use this USB Card:http://www.ioi.com.tw/products/proddetail.aspx?CatID=106&HostID=2035&ProdID=1060136Hopefully the work with the ESXi. In need to open the Server and plug them in.

author: CopperCone
author_rank: Super Contributor
timestamp: July 01, 2018, 02:38:18 pm
content: Quote from: xaxaxa on July 01, 2018, 04:01:58 amWhat's your opinion of the plutosdr in terms of design and noise?

author: CopperCone
author_rank: Super Contributor
timestamp: July 01, 2018, 02:43:37 pm
content: Quote from: Lord of nothing on July 01, 2018, 08:50:00 amI don't know. I would need to test it, but I did not have a particular test in mind. All I could think to do is maybe hook it up and set some kind of narrow bandwidth with high gain, then jump around the spectrum a bunch to see if any peaks appear. I got the cable but I got side tracked and never touched the PLUTOSDR I have again. The only mod I made is I put a shield tape layer over it because I had some microwave antennas running at the time doing experiments with reflections and stuff and its plastic case annoyed me.Do you have some kind of algorithm or something (I mean this in general, I can do it manually if its not too crazy) I can use to paint some kind of performance increase metric? Like what settings to use etc.I also don't know if I should leave it open but shielded (with a SMA cap), 50 ohm terminator, open, shorted or something else. I only have the PLUTOSDR for doing RF spectrum.Well I do have a digitizier for my HP70000 but its kind of crappy (20MS/S), very well built though. I got very burned out doing the microwave stuff partially because you can't do anything cool without spending a shit load of money, which I did, but I need a shitload more. Also need to finish the house.. I want to install foundation drains/mess with hydrostatic pressure, radon removal, redo underfloor heating, fix the plumbing, add air ducting, redo the electrical, lighting, general finishing, then I can have a proper RF lab down there, it got very cramped where I am also with all the amplifiers and stuff I needed, to the point where working just irritated me. Now I just need $. I am not doing shit unless I get those drains installed because I just cannot tolerate having the god damn foundation leak water around a bunch of super expensive crap. I just wont do put any money or risk into that location until I can do something about it. Also need alot of shop furniture because there is a serious lack of dust control on things like toolboxes etc, with adhock cheap ass shelves, planks of wood, exposed walls being used as shelves, stuff hanging from copper wire, its just not kosher in any regard. I want a few more tool chests, maybe one of those tool chest table things.. all expensive, but I can wheel them out of the way to do floor cleaning and stuff easily. Right now its just a time trap for people that have even mild OCD, best to avoid cleaning it or you will be down there forever.........Same thing with the attic, I want to transform it into a temperature controlled, insulated sealed attic with HVAC system, then I could have some end of the line equipment up there, related to antennas.. right now you need to avoid nails sticking out of the roof.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 01, 2018, 02:56:03 pm
content: Quotethere are many ways to make legal Money.Why not move?Try to get an Job in the NSA, CIA, Military Spy Station in Germany.

author: CopperCone
author_rank: Super Contributor
timestamp: July 01, 2018, 03:00:39 pm
content: Quote from: Lord of nothing on July 01, 2018, 02:56:03 pmbecause clearance...besides clearance is a joke, you get random ass untrustworthy people getting clearance, plus it gets stolen (probably more then is publicized), so then you are a target for coercion and stuff by foreign government because some someone stole some list, like what happened in 2014-2015.Then the internal investigations knows the list got stolen, so they are obligated to investigate people, who might have been approached, so you might have investigators crawl up your ass despite being a patriot, or at least spy on you. I don't want to be working as an intelligence official in a foreign country basically being worried about some highly centralized list being stolen and sold to that country by the Chinese. Then you might get a buncha heroin planted in your house, kidnapped, framed 50 other ways or otherwise menaced or even experimented on. My stress level would be too high because of how its structured right now. I don't trust it.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 01, 2018, 03:07:08 pm
content: WAT! I never say that you should steel something!You can apply for some Signal Analyst Job and make Money with your new Job.

author: CopperCone
author_rank: Super Contributor
timestamp: July 01, 2018, 03:12:10 pm
content: Quote from: Lord of nothing on July 01, 2018, 03:07:08 pmYea but then you need to get a secret or top secret clearance, so this office some where in DC has you on a list, that got stolen before and probably will be stolen again and people are probably trying to steal it all the time, so eventually when it does get stolen, they know you have clearance and possibly involvement with programs of interest.. then its just luck of the draw to see if enemy spies will try to turn you, or get you to willingly sell information, or for friendly spies to start spying on you because they think you might have thought that you were approached.Also someone confident that you will sell information or be intimidated might just get angry and kill you if you try to turn them in or stand up for yourself (since he revealed himself and is likely to be compromised). Or your 'friends' might get angry you are afraid to turn in the enemy (i.e. you might feel like you will get killed if you do anything other then refuse, say it turns out a coworker in a nearby department is a spy looking to expand his network of informants but for some reason he is just a really scary dude, like with organized crime connections or something), or test you preemptively with a fake enemy spy. I am not suited for this. I am too paranoid and anxious.Maybe there are low tier jobs that are 'safe enough' but I would always worry that the information I have is more valuable then it really is.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 01, 2018, 03:33:07 pm
content: ... You should not steal anything...I dont know why do you think about that.I never stole anything or spy on someone.Ok ok I love to play with me SDR but just for good thing.

author: CopperCone
author_rank: Super Contributor
timestamp: July 01, 2018, 03:41:08 pm
content: I think we have a misunderstanding between us due to language maybe? In my opinion you don't need to steal anything. Enough that someonethinksyou might steal something for them or for someone else, for any reason, to have a problem. I'm just saying its kind of risky compared to normal jobs.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 01, 2018, 03:47:00 pm
content: I would never think about that.I hope someone here have experience with the USB -> Fiberglas Stuff.Its relay interesting for the SDR People.

author: CopperCone
author_rank: Super Contributor
timestamp: July 01, 2018, 04:00:15 pm
content: Well I did not really think about it when I was younger but when you find stuff like thishttps://www.telegraph.co.uk/news/uknews/crime/11952973/Spy-in-bag-Gareth-Williams-was-murdered-by-Russian-hitmen-after-sexual-photo-blackmail-plot.htmlHe was not really a spy, just a mathematician that worked in a non-secret office. I hate to think about what happens to secret spieshttps://en.wikipedia.org/wiki/Death_of_Gareth_WilliamsNo one is really safe in that fucked up international 'game'Worrying about run of the mill crime is enough for me.It also seems to me, that either russia is good at hiding it, or recently they just increased activity. I studied organized crime some what and I see a kind of similarity to NY gangster roy demeo's crew, in the sense that once they started killing people, the frequency just increased, because they realized how convenient it was, like positive feedback. Kind of like they decided to just lower the bar for killing people after a while, for smaller amounts of money or more petty stuff. Then it kind of just turned into a addiction/business for them, and if you looked at what was going on, it was much different then how the rest of the mafia did business in new york.I think the same might be happening in russia, based on what I have been reading since probably 2008, but maybe its because of the prolonged ukraine conflict and instability in syria thats making them go batty. War makes them all bleed through more. Anyway fuck that bs.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 03, 2018, 02:39:52 pm
content: Does anyone here use an USB -> Fiberglas thing?