Using a USB device 50 to 100 feet from PC?

Factual Questions
1

How might I be able to use a USB device - a little GPS receiver, sometimes called a “GPS mouse” because it looks like a computer mouse - outdoors where it can see the sky, and still have it connected to my PC, which is in my basement office?

I think USB cables per se can only be about 15’ long. Is there some kind of USB repeater? Can I chain together USB hubs every 15’? I have a CAT5E hardwired network throughout my house, and plenty of cable too - is there a device that acts like a remote USB port for my PC and plugs into the network? I have a USB print server, which kinda looks like this last idea, but I don’t know if it can only service USB printers or if it can service any USB device I want.

If I could do something to reach even 30’, it would be somewhat useful. If I could have any length I wanted, about 70 feet or so might be ideal anyway.

Does the answer depend in any way on the USB device I want to use? That is, do their abilities to be reached vary?

Also, the PC I want to do this with used to have USB 2.0 ports, but since an OS reinstall they all look like USB 1.x ports. I haven’t fixed it because that has handled everything I have wanted to do OK so far, and because a half hour of fiddling with it didn’t turn anything up. Any reason this extension project might require fixing the 2.0 issue?

Thanks!

2

This gets you 150 feet: http://www.smartvm.com/USB-EXTENDER-VIA-CAT-5-EXTENDS-1-USB-DEVICE-INCLUDING-KEYBOARD-OR-MOUSE-P7243.htm

3

I have a need for something similar, both USB and RS-232 serial. I’m looking into wireless solutions, but have just started – sorry I don’t have better information at this point, but I thought I’d throw it out there as an idea as it sounds like you’re only considering cables.

If I get the chance to do the research and come across something (I expect to be busy the next couple days), I’ll certainly post what I find out.

4

RS-232 will go hundreds of feet without an extender.
I have done some design using wireless RS-232 solutions (Aerocomm) and they don’t work in all applications, because the radios introduce significant latency.

5

Why does it have to see the sky?
GPS devices work by receiving radio signals, which often penetrate into buildings. Many GPS devices work fine inside buildings.

I’d test it out before spending money on a USP extender.

6

>Why does it have to see the sky? GPS devices work by receiving radio signals…

I know there can be some signal inside buildings but it is never as good as the roof. In fact, my roof isn’t as good as I wish, because of surrounding trees, and I sometimes mount receivers on masts to reduce this problem.

I’m doing surveying with postprocessing of code phase, carrier phase, and Doppler frequency shift. This can get positions down to several inches, but performance depends very strongly on seeing lots of satellites with minimal interruptions. I am mounting a unit on my house to use as a base or reference station.

7

Let’s put it this way - my exceptionally sensitive Holoux GPSlim240 didn’t work worth beans in Venice - probably the city with the worst “Urban Canyons”.

8

I used this device (pair of devices, actually) to extend a USB connection into a bird box in my garden - for a nest box cam.

http://www.smartvm.com/USB-EXTENDER-VIA-CAT-5-EXTENDS-1-USB-DEVICE-INCLUDING-KEYBOARD-OR-MOUSE-P7243.htm

It works just fine - and gives you up to about 150 feet over Cat5

9

I’m glad I’m in good company.

10

Oops… Saw your link but didn’t click it - and didn’t notice that my product search came up with the same one. Anyway, I was chiming in from the personal anecdote angle, yeah, that’s what it was.

11

I understand the general question, but I’m wondering why you need regular updates from a non-moving GPS? Couldn’t you just use a sneakernet here? (In other words, walk outside with the GPS, take the reading, walk back to your computer, enter the lat/long. Repeat whenever your house moves more than 10 feet).

12

I’m afraid I spent a few minutes thinking about USB technology before coming up with this answer. :smack: (Incidentally, the only new thing I could think of was Wireless USB, but it apparently doesn’t really work the way I thought it might, and in any case is even more distance limited than the wired version, so scratch that.)

13

>I understand the general question, but I’m wondering why you need regular updates from a non-moving GPS? Couldn’t you just use a sneakernet here? (In other words, walk outside with the GPS, take the reading, walk back to your computer, enter the lat/long. Repeat whenever your house moves more than 10 feet).

That’s not the information that is being recorded. There is a binary data stream coming from the GPS. It includes the phase angle of the arriving carrier wave and the estimated distance between the receiver and the satellite, for each satellite. There is also ephemeris data being periodically downloaded from the satellites with estimates of their orbital elements, and WAAS correction information. This GPS device looks like a computer mouse without the buttons or sensors. It doesn’t have a display. The desktop computer is running a special program that came from the GPS manufacturer, to control the receiver and to log all these data into a RINEX file.

To tell you the truth, I am not even sure whether latitude and longitude and altitude are part of the information yet. They should be calculable from all the pseudoranges, and they will also depend on information coming from another base station if I am still in the phase of this project that works out where my station is located (I have to do that first before I can treat it as a reference location for other measurements).

14

I’m still not sure what this is for.
Again, if you only need to do this once, to get your location, the easiest thing might be just running a regular (power) extension cord outside, and carrying the computer outside for an hour (or borrowing someone’s laptop).
If this is something you want to do every day, I’m honestly curious as to what it’s for. Sounds almost like what people used to have to do to get better precision when the data was encoded, but I’d be interested to find out what it’s used for now.

15

>Again, if you only need to do this once, to get your location, the easiest thing might be…
>If this is something you want to do every day, I’m honestly curious…

Oh. I want to accurately measure this location, and then use it as a base station when recording other nearby locations.

To accurately measure this location, I will postprocess the data I collect with CORS (constant observation reference station) data that somebody measures simultaneously and posts to the web as a public service. This has the effect of very accurately measuring the vector from the CORS to my location. Since there are CORS locations available every 10 or 20 miles or so around here, during the postprocessing I can estimate that vector to something like a millionth of its length (if I remember the number correctly), and the CORS location is very accurate.

Then, to survey other nearby locations, I can use my existing location as a new reference station. Since it can be closer to some of the places I want to go out and measure, I can get better accuracy on them. So when I am doing those other locations, I want to fire this system up too.

The postprocessing is always done with datasets collected simultaneously so the temporary errors can be taken out. Therefore I need my home station collecting when I am out in the field.

Actually, any dataset I collect in my home station can be postprocessed with CORS data to improve my estimate of the home station position. Therefore I can use home datasets two ways - as reference datasets for field work, and also to improve my existing home location estimate. I can reanalyze datasets whenever I want, so the more field work I do, the more accurate even my first field observations get.
>Sounds almost like what people used to have to do to get better precision when the data was encoded…

It’s still encoded. You can’t make any sense of it listening to it. Though some of us have listened to Omega navigation system broadcasts directly, without downconversion of frequency. They are (were?) around 10 kHz, so many people can hear them. Or used to be able to. You only need a wire antenna, an amplifier, and headphones. You don’t need a “radio”. But the signal isn’t very interesting, just a repeating pattern of beeeeeps.

You referring to Selective Availability? That’s not code, it’s deliberately added timing errors.

There are still several different codes, C/A and P or something like that. Civilians can only access one of them. And there are L1 and L2 frequencies, and most of us can only afford L1 frequency receivers.

I’m poor. My most expensive receivers in this system are $139 each.

16

OK, I bought a USB-1730 extender from Amazon (it was well reviewed but doesn’t have a manufacturer’s name on the product). It is supposed to work on up to 150 feet of Cat5e cable. It works on 10 feet of cable, and “sort of” works on 50 feet.

By “sort of”, I mean the GPS receiver I have serves two functions. One is to receive GPS signals. The other is to act as a dongle for the GPS post processing software. So, on 50’ of cable, the dongle function works (I can run the software), but the software dies when I try to use GPS data.

If I use 10’ of cable both functions work. Unfortunately, in the physical location I can reach with the 10’ cable, I can only see a few satellites and the data aren’t useable.

Any ideas? I wondered if perhaps the DC power to drive the receiver has lost too much voltage on the way and whether I could add some kind of booster at the far end.

17

I would try to power the far end locally…

18

>I would try to power the far end locally…

How? Can I cut the USB cable open and select two wires out of the four and wire them to a DC source? Do you know which wires?

The GPS device, by the way, doesn’t accept power except through the USB connection. There’s no separate power jack.

Can you buy a USB adapter of some kind that lets you add your own power?

19

You could try making a USB breakout connector - use a USB extender cable (Male to Female) and then cut the power line in the middle. Here is some information that might help: WEBSITE.WS - Your Internet Address For Life™

20

That looks doable. Do you happen to know if I could add a USB Hub out there at the business end, if I find a Hub that has a separate power input? I’m not sure if I can find another hub or doctor a cable and find a power supply sooner.

Thanks for the help, beowulff!