Web SDR with RTL-SDR dongles.

[ON5HB]

Hi there,

I'm using RTL-Dongles to drive my websdr online receiver.
At the moment 2 dongles in use, for 160~80M shortwave and 2M VHF.
The plan is to install 4 or more dongles over time to cover more Ham-radio bands.

Used hardware:

2x RTL-SDR v3 dongles
1x Upconverter 125 MHz (direct sampling is possible with patched rtl_tcp drivers but too much mixing products)
1x Dual-core 1.1GHz Intel Celeron running Debian

Have fun playing with it: http://heppen.be:8091

For other SDR online receivers: http://www.sdr.org

Greetings,

Bas - ON5HB

[rtlsdrblog]

Very nice! Thanks for sharing, had a good time browsing.

[ON5HB]

I ordered 2 more dongles to add even more bands.
I wonder how long it takes before my USB 2.0 bus will overload

The direct-sampling works way good, as it doesn't have PPM problems, it's right on the freq that is tuned, no floating around.

I tried with an 125 MHz up-converter, but there is no difference, in fact it has less mixing (ghost) signals then without.

[ON5HB]

Problem solved!

I ordered attenuators and a NoElec Upconverter with TXCO.
The signal from my G5RV was overloading the dongles, so I added -10dB attenuator before the Upconverter.
Then after splitted the coax into 4 dongles, works great!

So I ordered another 2 dongles from you guys to add more bands.

These dongles are really good, direct sampling is nice and works but you can't regulate input gains, so they overload very quickly.
This is not a problem for people with a small antenna, but I'm using Ham Radio antenna's, they have a very high voltage level with big signals.
Heck if you touch the coax during static conditions (happens a lot) you will be shocked....as in electrocuted

Therefor the Upconverter is in place, it has protection and I can regulate the input-gain per dongle.
Current situation, see pictures.

4 dongles in use at the moment.

IMG_20180228_172720.jpg (741 KiB) Viewed 8998 times

Upconverter to protect overloading

IMG_20180228_172726.jpg (912.42 KiB) Viewed 8998 times

The hub is powered and can handle 10 devices

Lesson learned, first attenuate the signals with -10dB, then upconvert....works well.

[rtlsdrblog]

Looks good! Yes attenuation, or filtering may be required for direct sampling mode if you have a very good antenna.

But I worry about your statement that the antenna constantly shocks you with static. It sounds like your antenna is not grounded properly/safely, or doesn't have any ESD or lightning protection built in? If you have a large outdoor antenna prone to static you should be taking care of that first.

The dongles and ham-it-up do both and ESD protection, but I think with constant shocks either one could eventually wear out and fail.

[JEL]

Great pictures and setup

Which distances can you run the USB at with a powered hub?
I have run into issues when trying to go above 5 meter from the computer (Using unpowered USB extender cables, which do state they have a length-limit)
Can you get 10 or 15 meters if using powered hubs? Any downsides of using such devices?
I know they sell optical USB cables, but they cost a fortune.

About the 'shocking' antenna connection, here in Denmark the standard TV wall-outlet-connection will also shock you if you touch it. Enough so you learn to avoid repeating touching it once you've been hit a few times
DO take care!

[ON5HB]

I use a cable of about 1.5m in length.
But I use Belkin cables, those are very good and very thick wires, never had problems with those.
And the hub is Logilink 10 ports 2.0 with 3.5A 5V powersupply.

There is no shocking anymore, probably because I replaced the motherboard, it stopped doing so after.
Everything is grounded here to HF and heating earth.

Or it could be because I added 2 extra dongles, it's running 6 dongles at the moment.
Maybe in a few weeks again few more until the hub is filled

[Username]

Position?
Sadly here all my Ports are close so I cant access your SDR.

[n4but]

How did you get multiple dongles to get recognized in websdr? I need to use 3 dongles.
im currently using this line for one dongle:
device !rtlsdr 127.0.0.1:1234

while using rtl_tcp.

Is there a better way?

73
Nick N4BUT