Long USB-cable vs long antenna-cable?

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aurgathor
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Re: Long USB-cable vs long antenna-cable?

Post by aurgathor » Wed Jan 30, 2019 3:30 am

"I know of a max. of 40 m (~131 ft) if you cascade active USB 2.0 cables, like Delock Kabel USB 2.0 active 20 m USB cable Art.-No. 82690 price ~30 €. I used one cable with a Haupauge video grabber, but I never checked for RFI. "
That may be possible -- I just do not know for sure, and have never tried t. But as per my experience, theory and practice may be very different at times. :ugeek:

I tried some 'USB over Ethernet' adapters and if I need to describe them with one word: "suck"

"I have tried active and non-active USB extension-cables, and could not get anything working when going above 15 feet (which is not enough length for what I want)"

Obviously, with the USB 2.0 limit being around 16 ft (cables normally available up to 15 ft) the chances of a passive cable segment working above 16 ft is not very good, and with extension cables it can be less than that.

How did you hook things up?
Note well, you can't just cascade active extension cables without "injecting" some extra power.

My current long range USB cabling is as follows: PC -- 15 ft cable -- hub -- 10ft cable -- hub -- 6ft cable -- phone. And It works. Both hubs are externally powered and all cables are passive.

JEL
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Re: Long USB-cable vs long antenna-cable?

Post by JEL » Thu Jan 31, 2019 9:23 am

aurgathor wrote:
Wed Jan 30, 2019 3:30 am
I tried some 'USB over Ethernet' adapters and if I need to describe them with one word: "suck"
Thanks.
I won't waste time or money investigating that as an option then :)
aurgathor wrote:
Wed Jan 30, 2019 3:30 am
Obviously, with the USB 2.0 limit being around 16 ft (cables normally available up to 15 ft) the chances of a passive cable segment working above 16 ft is not very good, and with extension cables it can be less than that.

How did you hook things up?
Note well, you can't just cascade active extension cables without "injecting" some extra power.
I tried a few variations:

One 15' passive connected to a 15' active, for a total of 30' = no go.

One 15' passive connected to a 15' passive, for a total of 30' = no go.

They were all connected to a USB 3.1 on the PC.
And all were thick quality (according to their label and price) cables.

I will see how it goes with the long antenna-cable option when all the bits and pieces have arrived in the mail :)

hotpaw2
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Re: Long USB-cable vs long antenna-cable?

Post by hotpaw2 » Fri Feb 01, 2019 4:23 pm

Yet another possibility for connecting to a remote antenna is to plug an RTL-SDR directly into a tiny computer, such as a Raspberry Pi 3 or Zero W, and put that near the antenna. Then run rtl_tcp on the Pi, and use either a long ethernet cable or WiFi from the Pi to connect to your router or desktop/laptop computer.

This allows you to put your antenna potentially miles away (or anywhere on the planet) if you can get a network cable (fiber?), WiFi, or commercial internet to the antenna site. A pair of directional WiFi antenna's might help with the max WiFi distance. You do have to figure out how to get reliable 5V power to the Pi, perhaps via a linear regulated battery with a linear regulated solar panel to recharge the battery.

I use just this method to connect to my home antenna from my iPhone on the road (anywhere with high-speed WiFi) with my SDR iOS app. But you could use the same path with your laptop.

aurgathor
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Re: Long USB-cable vs long antenna-cable?

Post by aurgathor » Sun Feb 03, 2019 9:54 pm

"I won't waste time or money investigating that as an option then :)"

I forgot to mention that they were cheap dongles from eBay and more expensive dongles may perform significantly better, but make sure that anything expensive you try has a money back guarantee.

One issue I identified with them was excessive voltage drop over longer cables, and I planned to modify one dongle to use an external PS, but I never finished that project, and my USB extension seems to be very reliable.

"I tried a few variations:
One 15' passive connected to a 15' active, for a total of 30' = no go.
One 15' passive connected to a 15' passive, for a total of 30' = no go."

They are both DOA. Try what I mentioned in my previous post -- 10 / 15 ft long passive cables between externally powered hubs. I got 4 - 5 USB 2.0 hubs for $1 apiece from a computer recycle place a couple of a couple of years ago, but inexpensive 4 port hubs can be had for $5 - $10 new. The really important thing is external power -- that's a must.

JEL
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Re: Long USB-cable vs long antenna-cable?

Post by JEL » Tue Feb 05, 2019 9:03 pm

I haven't seriously considered the Raspberry Pi, but maybe at a later stage I will look into that (if all else fails totally)
Thanks for the suggestion :)

I just got a few parts in the mail, so in the next few days I will test the long antenna-cable option.
I am hoping that will go well, but we will see :)
If I get fair results with that, I might settle and not try to push this setup any further (it is, after all, still just an indoor-placed antenna, so that probably is the main limit I will face anyway)
I will post back my results when I have done some testing and evaluation.

Thanks all :)

Username
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Re: Long USB-cable vs long antenna-cable?

Post by Username » Wed Feb 06, 2019 1:07 pm

In my case the Pi them self produce A LOT OF uggly Noise! Its was impossible to use the SDR with the Pi!
I play arround with that: https://www.icronshop.com/fibre-usb-ext ... raven-3124
With one SDR the work. The major problem is if the Temp get colder <10c the lost contact with each other. :evil:
Even the support dont know what happened. I guessed some cold solder joint.

JEL
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Re: Long USB-cable vs long antenna-cable?

Post by JEL » Fri Feb 08, 2019 5:05 pm

Yes, I am worried about that too (adding an extra computer, since in my experience they are some of the worst noise-offenders, along with television-sets. At least those 2 device-types are those that make most of the noise I find here in my setup)

I am currently testing a 45' (15 m) antenna-cable, and the results are good.

I accidentally discovered how noisy a USB-extension cable really is (or can be, at least), since my initial routing had the antenna-cable laid out along a USB-extension (an extension used for other purposes)

Whenever the computer was using the USB-device, it would create huge spikes all over the spectrum.

I solved this by making sure the 2 cables are not near each other.

But it was a clear example of just how much noise USB creates (or broadcasts)

The main potential issue I feared I would have with the long antenna-cable was a loss of signal (lower SNR), but I don't observe that with the current length.

I did actually try an amplifier at the antenna side, but it did not improve the SNR (in fact it reduced it) even though the overall signal strength was boosted.

So it seems that this antenna-cable length is not long enough to cause any real problems.
How much noise it picks up is of course difficult to measure, since I can't make a comparison-test without physically moving the computer closer to the antenna (which is more involved than I want at this point)

But I assume (always dangerous to do though :) ) that it would likely be worse to have a long USB-cable than a long antenna-cable, since a long USB-cable would, by default, take the computer-noise closer to the antenna (as per the accidental discovery mentioned above)

At the moment only the antenna-cable is 'linking' the computer and the SDR, which means computer and USB-cables are not in the same room as the antenna.

Had I used a USB-cable extension all the way I would obviously have the SDR and all the USB-noise in the same room as the antenna, and my assumption is that that would probably have made things worse (now that I have seen how much noise USB really broadcasts)

So I dare conclude: longer antenna-cable is better than longer USB-cable :)

Thank you all for your input :)
jacob.

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ab1jx
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Re: Long USB-cable vs long antenna-cable?

Post by ab1jx » Thu Feb 28, 2019 10:45 pm

You can spend big bucks on fancy coax with N connectors and all that. The only real advantage over an rtl_tcp setup is that the coax tolerates temperature extremes better, like in a attic or outdoors. RG-6 isn't bad and its usage in TV has brought the price way down. Don't worry about the 75 vs 50 ohm difference. Probably a mixture is the answer, run coax to where the temperatures are reasonable, stick a Raspberry Pi there to run rtl_tcp on, then network wire to where you're going to run it from. You'll need to reboot the Pi from time to time anyway so you don't want it on the roof. Hdsdr (for one) can work fine over a TCP connection with the antenna/Pi up to 100 meters away. And network wire is cheaper than coax.

JEL
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Re: Long USB-cable vs long antenna-cable?

Post by JEL » Sat Mar 09, 2019 6:08 am

Thank you ab1jx :)

I'm still testing the current antenna-cable setup and so far the results are as good as I believe I can get here, so I think it's going to end up being a permanent setup.

I can't get the antenna outside, so reception options are probably very limited whatever setup I use.

aurgathor
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Re: Long USB-cable vs long antenna-cable?

Post by aurgathor » Sat Nov 09, 2019 5:13 am

I just verified that the RTL-SDR v3 will work fine over a chain consisting of 5 USB hubs and 6 USB cables. With 15ft long cables between the various devices that could cover up to 90ft, although the total amount of cabling in mine is slightly less than 40ft at the moment.

I should have at least 2 - 3 more hubs somewhere, but I need to find them first.

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