Analog cable TV USB is detaching; related with power/antenna

mv · Watchman Joined: 20 Apr 2005 Posts: 6747

This is a real hardware-only question for electro-engineers:

I have an analog (over cable) TV USB stick (sundtek) attached to a USB3 port.

Now my problem is that whenever something in the house needs some power (microwave, vacuum cleaner, freezer, ..., even if this device is far aways and runs over a different fuse), the stick gets detached, i.e. the kernel reacts as if it has been drawn; sometimes it is "reattached" for a few seconds (or sometimes less), but esentially it works only again if the power device is switched off.

The strange thing is that no other USB device is affected, and moreover, this does not happen if the antenna cable is removed.

So it appears that I need some sort of isolation of the antenna "power" (the antenna is fed by some cable provider).

Does such an "isolation device" exist or can be built?

Dominique_71 · Posted: Tue Oct 28, 2014 6:14 pm Post subject:

Such "isolation" devices are high frequency transformers. The radio amateurs call then baluns.

Your issue is very strange. I think more for a problem with the ground. An antenna installation must be grounded at the earth potential. Maybe just to put a wire between the ground of your antenna and a water pipe can solve your issue. Otherwise, for such a balun transformer, I would talk with some radio amateurs about it, because they are the only I know using such devices, and they know how to calculate and make them.

EDIT: Be aware a water pipe is not a regular electrical earth. In most countries, it is even completely forbidden to use them for that.
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mv · Watchman Joined: 20 Apr 2005 Posts: 6747

Thanks a lot. I do not understand much about "ground" and why it is necesary, but I was also somehow suspecting that perhaps the "ground" of the cable and of the computer "differ". Perhaps I should try to connect them...

NeddySeagoon · Posted: Tue Oct 28, 2014 7:58 pm Post subject:

mv,

Tell us more. I assume the cable TV comes into your home and is terminated in a powered box of some kind?
Then you have an "antenna" cable from this box to your system.

Is your system a laptop or desktop?
Does this happen if its battery powered - with the power brick disconnected?

Beware plastic waterpipes if you are trying to use them for a ground :)

Incidentally, too many grounds are as bad or worse than incorrect grounding. Then you get ground loops, which cause noise due to the induced currents caused by the AC in the power distribuion system in your home.

Ideally, you need the grounds connected to a single 'star point', so there can be no loops but safety considerations associated with operating each piece of mains powered equipment independantly usually make that impossible.
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Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

mv · Watchman Joined: 20 Apr 2005 Posts: 6747

NeddySeagoon · Posted: Tue Oct 28, 2014 9:29 pm Post subject:

mv,

The cable company will bring in one cable to a distribution amplifer, which will feed all the flats.
Its like a signal booster but with more outputs. It will be powered but its outside your control/influence.

Is your USB dongle USB2 or USB3?
A USB3 port can provide more power than a USB2 port so it should not be a power issue.

Can you put the output of lsusb -vvv onto a pastebin so we can check out your USB device tree.
Do you have other USB ports you can test with?
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NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

mv · Watchman Joined: 20 Apr 2005 Posts: 6747

John R. Graham · Posted: Wed Oct 29, 2014 7:28 pm Post subject:

@mv, what's the external connection to this device? RG-59 coax?

- John
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mv · Watchman Joined: 20 Apr 2005 Posts: 6747

NeddySeagoon · Posted: Wed Oct 29, 2014 8:23 pm Post subject:

mv,

You have four USB Busses (root hubs). The controllers are

mv · Watchman Joined: 20 Apr 2005 Posts: 6747

NeddySeagoon · Posted: Wed Oct 29, 2014 9:20 pm Post subject:

mv,

This is a long shot ...

Some motherboards have an option to pawer some/all USB sockets from the +5v STBY.
Its a bad idea in that it is a poorly regulated low power supply but its always on, so a connected USB device can wake up the box.

Do you have such an option?
How is it set.?

Tell us your motherboard ... dmidecode will save you looking inside.
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Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

mv · Watchman Joined: 20 Apr 2005 Posts: 6747

NeddySeagoon · Posted: Wed Oct 29, 2014 10:29 pm Post subject:

mv,

Its usually a jumper, or several jubpers on the motherboard.
I was looking for

John R. Graham · Posted: Thu Oct 30, 2014 1:18 pm Post subject:

John R. Graham · Posted: Thu Oct 30, 2014 1:30 pm Post subject:

mv · Watchman Joined: 20 Apr 2005 Posts: 6747

The motherboard is MSI B85M-P33, and I also found a motherboard handbook to download (8 MB PDF, zipped). However, I could not find much useful concerning USB in it.

I guess I should find some cable for grounding. Is it correct to assume that the "outer" part of the cable adapter will be the ground one?

Antenna cables here in Germany look different: They are all like on this picture (male and female, respectively).

NeddySeagoon · Posted: Thu Oct 30, 2014 3:19 pm Post subject:

It can also be a damaged connection between the PC and the building distrbution amplifer, so that there is no ground provided domn the antemma cable.
The antenna ground wends its way through the mains grounding system back to the distrbution amplifer instead. This gives you a huge loop to pick up switching spikes.
The problem need not even be in your equipment nor in your flat.

If you have a multimeter, its easy to test by measuring the resistance from your unplugged antenna cable outer contact to mains ground. It should be very low.
Be careful not to hold the mutimeter probes while you make the measurment. It you get the right answer, it would have been safe. If you get the wrong answer and some other equipment in the building has a earth fault at the time you make the measuremet, there could be mains voltage across your two contact points. The multimeter is expendable ... you might not survive.

Do you have access to other antenna points?
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Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

mv · Watchman Joined: 20 Apr 2005 Posts: 6747

NeddySeagoon · Posted: Thu Oct 30, 2014 3:38 pm Post subject:

mv,

Your motherboard (page 11) has two jumpers JUSB_PW1 between the VGA connector and the CPU an JUSB_PW2 between the PCIe 1 lane slot and the edge of the board.
Page 13 lists them as 2x USB power jumpers.

Page 24 explains hom in set the jumpers.

The default settings are what you need. The USB ports then do not support wakeup and are powered from the real +5v, not 5v STBY.

References are to the English vesion of the manual.
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Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

mv · Watchman Joined: 20 Apr 2005 Posts: 6747

John R. Graham · Posted: Fri Oct 31, 2014 2:38 pm Post subject:

mv · Watchman Joined: 20 Apr 2005 Posts: 6747

Thanks to your link, I found the German names for these devices: The english term "ground-loop isolator" is used as well (or sometimes "Masse-Trennfilter").
There exist even some directly for antenna. I guess I will get one (in some days when I have more time).