[NLRS] First tests with DVB-T dongle

[S. Earl Jarosh]

Check out

http://wiki.spench.net/wiki/RTL2832

For some source code 

BTW where can I get a couple to play with?


S. Earl Jarosh, N0HZ
Cell:  612.868.1313
Off:   763.545.3275
Home:  763.546.7897
Fax:   763.546.7897
earl at moneycenters.com

 
-----Original Message-----
From: nlrs-bounces at mailman.qth.net [mailto:nlrs-bounces at mailman.qth.net] On
Behalf Of Doug Reed
Sent: Sunday, July 15, 2012 7:14 AM
To: Northern Lights remailer
Subject: [NLRS] First tests with DVB-T dongle



A friend dropped off a couple RTL2832/E4000 DVB-T dongles today. The dongles
are kind of generic. One is white, standard USB size, the other is a black
square mini-dongle. No distinguishing features except they are both RTL2832
based.

The dongles are interesting because raw IQ data samples from the receiver
chip can be routed to the USB port and captured by the computer for further
processing. So with the proper software it becomes an SDR receiver that is
good over the full range of the E4000 receiver chip. It will cover all the
ham bands from 2M to 1.3GHz including most of the range from FM broadcast to
GPS. This is well beyond the published range for the chip and seems to
depend on actual component values in the dongle.

A lot of active development work is being done on the Ultra-Cheap-SDR Yahoo
group. Based on my reading, there is a lot of different software packages
that will work. But the easiest to get working (currently) seems to be the
SDR# (SDR-Sharp) program using USB drivers from the ZADIG project. That is
what I chose to do and it installed easily on two different laptops.

As expected from the install directions, the 1.4GHz Atom N270 CPU in the
Mini-9 netbook is too slow to run cleanly, the audio skips because it can't
keep up, but it did try to receive FM from 102.1MHz with the spectrum
display and waterfall working. Both dongles worked. I didn't look closely at
either one to know if one or the other was performing "better" for receive
sensitivity.

I then installed on a HP Compaq 6710b laptop with a 2GHz Centrino Core-Duo
CPU. Again, both dongles worked fine, this time including FM stereo audio
with no drops or stutters while displaying the spectrum and waterfall. The
waterfall makes it easy to see intermittent or weak signals. In the FM band,
that isn't a real problem. I preferred to turn off the waterfall and get a
larger spectrum display.

What I'd really like would be a "poor man's spectrum analyzer" type program
for the dongle. Adding peak hold to the current spectrum display would go a
long way toward what I want. Adding some secondary processing to act as a
modulation analyzer would make this a wonderful tool for repeater owners and
anyone else wanting cheap "test equipment."
The dynamic range is limited by the 8-bit ADC so there are some things it
can't do but still one heck of a lot it could do....

OK, so now I have a $20 dongle that turns a 8 pound laptop into a $10
transistor radio..... If it could replace a $1000 spectrum analyzer and
provide some modulation analyzer functions, that would be a much better
exchange ratio....

For simple signal reception, the SDR# (SDR-Sharp) program seems to do a good
job on WFM anyway. It supports Fun Cube, RTL2832, and SoftRock hardware
devices and multiple modes with WBFM, NBFM, AM, SSB, CW as standard options.
I haven't tried to find any narrow band FM or aircraft signals yet, but
supposedly others have done that. It can NOT decode ATSC digital TV so don't
even ask.

I do wish the SDR# software had some "save setup" features and a way to
extract and display more data about the dongle and what it is doing. And I'd
need a way to take a partially decoded data stream and pass it out to a
second program to finish the decode.... There is still too much I don't know
about the software and hardware, but what can you expect for 30
minutes........

73, Doug Reed, N0NAS.


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