Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: RTL DVB-T dongle faulty?  (Read 10998 times)
G7MRV
Member

Posts: 481


WWW

Ignore
« on: February 27, 2014, 07:43:04 AM »

Ive just taken delivery of an RTL DVB-T dongle, which I suspect is faulty, im wondering if others with more experience of these could help confirm this?

I am using it with SDRsharp, and have tried it on two different PCs - my desktop and my toshiba laptop. On neither will it pick up anything other than the very strongest signals.

It is a little off frequency but thats not a big concern at present. The noise level on the SDR# waterfall shows as -50dB all the time, although it does vary a little with different antennas. This is the same even with the antenna disconnected.

I have SDR# set up just 'as it comes' with the RTL device RF gain at 0. Ive tried varying the RF gain, selecting/deselecting the various AGC controls, but although the noise level then changes, theres no improvement in reception

Have  I a bad unit, or something wrong in my setup of the software? What figures do others using these R820T based dongles get?

Logged

KA4POL
Member

Posts: 2094




Ignore
« Reply #1 on: February 27, 2014, 10:27:50 AM »


The noise level on the SDR# waterfall shows as -50dB all the time, although it does vary a little with different antennas. This is the same even with the antenna disconnected.


If there is not much variation between antenna and no antenna, are you sure, the antenna connection is good?
Logged
G7MRV
Member

Posts: 481


WWW

Ignore
« Reply #2 on: February 27, 2014, 02:25:48 PM »

It looks like it might just be due to local noise. Moving the device away from the computer makes quite a difference.

The results with the laptop might have been skewed by a) it being a rubbish laptop with an almost failed battery, and b) the proximity of the several hundreds of kW of UHF we broadcast!

Further experimenting has resulted in much better results, still not perfect, but I think im learning better how to drive this thing

Comparing with screenshots online, it seems most show a rather high base noise level, I guess a quirk of the device.

I will hopefully soon get it connected to my discone, but at present dont have a suitable adaptor to hand
Logged

KD7RDZI2
Member

Posts: 73




Ignore
« Reply #3 on: February 28, 2014, 11:34:23 AM »

I have seen two cases of faulty RTL dongles. The first one was at the USB side as it could not be detected by any computer, and this is not your case. The other case was transmitting on HF while trying to listen the RTL on VHF. T That happened because that RTL had no band pass filter and more likely no RF protection at all. So I would advice never transmit on any band while listening to the RTL unless you are pretty sure you took all RF precautions.

Transmitters nearby may desense the RTL. Bandpass filters or RF notch filters may help a lot in reducing unwanted signals.

It's normal to see on SDRSharp about -50/60db. Don't be fooled, they are db, not dbm! As it happens that the RTL has a dynamic range similar to these values you do not need to see a noise floor of -130db!
Logged
CHRISTOFERO
Member

Posts: 24




Ignore
« Reply #4 on: March 01, 2014, 09:14:33 PM »

I know a lot about the little dongles and I can assure you that almost everybody has that problem at the beginning because they usually don't consider the heavy duty RF noise around their computers. What you need is a USB extension, some ferrite split beads, and a decent antenna.

Use an adapter to allow you to use RG6, CATV coax instead of the unspeakably low quality wire that comes with the antennas to lower costs.

Over on the Reddit forum there is lot of discussion of antennas, etc. Generally a discone is a good choice. Try to feed it with the best quality coax you can find to preserve its high frequency performance.

If you have any questions, on them, PM me.
Logged
G7MRV
Member

Posts: 481


WWW

Ignore
« Reply #5 on: March 02, 2014, 01:50:37 AM »

I know a lot about the little dongles and I can assure you that almost everybody has that problem at the beginning because they usually don't consider the heavy duty RF noise around their computers.

Exactly right!  Its easy to forget to consider that this is a very low cost device, and as capable as it is in many ways, it must be remembered that its in an unshielded plastic box, with a front end wider than a Zeppelin hanger door!

I have a 3m USB extension on order, and I use my loft mounted discone (fed with Time Fibre TF-10). The dongle now has been modified with a TNC connector and RG-178 for the antenna connection. It will be going in a small die cast aluminium box shortly

As Ive found out, a few simple precautions, a decent antenna, and this thing might not be a world class radio, but it sure as hell is fun!
Logged

K4LJA
Member

Posts: 21




Ignore
« Reply #6 on: March 03, 2014, 07:14:07 AM »

If you have any questions, on them, PM me.

I would like some help in getting SDR-Radio up and running with my RTL Dongle, but I can't find your PM address on this site.

I have it working with SDR# and HDSDR --- but always strike out with SDR-Radio.  I use an HP all-in-one Omni 100 ... and with SDR-Radio I do not know whether to use 32 or 64 bit mode for loading the three required dll's.

Any help would be appreciated.  Thanks very much in advance ---

Randy  K4LJA
Logged
N0IU
Member

Posts: 1350


WWW

Ignore
« Reply #7 on: March 03, 2014, 07:10:53 PM »

You might want to join the SDR-Radio Yahoo group: https://groups.yahoo.com/neo/groups/sdr-radio-com/info
Logged
K4LJA
Member

Posts: 21




Ignore
« Reply #8 on: March 04, 2014, 07:11:33 AM »

I did.  Thanks.

Randy  K4LJA
Logged
WB8VLC
Member

Posts: 125




Ignore
« Reply #9 on: March 13, 2014, 11:25:12 AM »

I have tried several RTL dongles also and every one of them had the same problem, they are basically junk and the software interfaces are all a cobbled up mess.

It's almost like the same software company that did "Health Care . Gov" did the software for these USB dongles, that's how frustratingly poor they are.

I tried Win XP, Win 7 and 2 versions of Win 8 and even though the proper DLL's are in the correct directories for 64 and 32 bit OS's,  the crappy Zadig program or whatever this piece of junk is called for USB control pukes every time it is run.

This is after weekends of installing and uninstalling the software on 3 different PC's.

 Save yourself the frustration and don't waste your time on these crappy USB dongles, get a real SDR made for HF or do as I did after which I connected my good old reliable Kenwood TS690 and got on the air.

It's refreshing not to have to worry about a crappy PC and crappy software interface crashing in the middle of a QSO.
Logged
N0IU
Member

Posts: 1350


WWW

Ignore
« Reply #10 on: March 14, 2014, 04:25:21 AM »

I have tried several RTL dongles also and every one of them had the same problem, they are basically junk and the software interfaces are all a cobbled up mess.

The only thing I can think of is that you must be incredibly unlucky when it comes to picking out RTL dongles. I bought the cheapest one I could find ($9.97 - including shipping from China). I read and followed the directions for installing SDR# exactly as written and I have never had one single problem with the hardware or software.

As far as the software, its free. It is "cobbled" together because some of the plugins are not written by the author of the base program.

No, it won't compete with a "real" purpose-designed SDR system, but for less than $10, it is what it is and I think it works great!
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!