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November 17, 2014, 4:14 am
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soundchip. The netbook I write this on has a Realtek sound chip. With their
engineering experience they now market a RF A/D, the RTL2832U with a sample
rate beyond 2 MSps. That gives a spectral display greater than 1 MHz. It is
combined with a Rafael Micro R820T silicon radio with a frequency bandwidth
from 24 MHz to 1.766 GHz. Below 24 MHz signal goes to zero. Above 1.766 GHz
signal is noise only. The system has autogain with steps from 0 to 49.6 for
an effective six bits. There is setable gain which seems to be set at 4000.
The A/D converter produces a stream of eight bit samples, so with the
autogain the device is effectively a RF 14 bit A/D.
The dongle is sold as a DVB-T + DAB + FM device. The manual on the install
CD is in Spanish and is directed at an audience in Peru. DVB-T is a digital
TV standard not used in North America and DAB is obsolete. This device costs
less than a head of broccoli on eBay and because is so neat expectations are
that $20 billion worth will be sold by 2020.
There device is worthless on Windows. Linux is supposed to be so
sophisticated but Linux software for this device is next to useless.
Good software for this device can be had on Google Store for a song. I have
connected my SDR dongle to my Android dongle using the OTG USB port. My
Android "PC on a stick" cost $60. If you don't understand a $60 Android
dongle, you would be better off with a $500 Android tablet. But eventually I
will get around to writing up the proper set up of an Android dongle.
I have three inexpensive Android programs for my SDR dongle. ADSB is an
RTL-SDR program for monitory airtraffic control radio. My SDR dongle come
with a tinker toy antenna so only random noise is detected. Also I am miles
from a flight path or an airport. I would need a good antenna.
I have ordered an SMA plug/F-connector adapter so next I will connect my SDR
dongle to my $20 Israeli UHF log-periodic Yagi antenna. A wideband fractal
antenna for this device is described in the ham literature.
SDR Touch and Wavelink Plus are two programs that work. SDR touch shows a 1
MHz wide RF spectrum and waterfall display. Wavelink Plus outputs a lot of
numbers. Because of my observations I have submitted a complaint about the
FM transmissions of a local broadcaster and they have corrected their
I have used SDR Touch to confirm the input and output frequencies of my
Baofeng UV-5R handheld VHF/UHF transceiver. However, VHF repeaters are
generally set with an offset frequency of 600 kHz and the 1 MHz spectral
bandwidth is barely adequate for a meaningful analysis. In UHF ham repeaters
use an offset of 5 MHz and so this device cannot do analysis.
Youtube is full of tutorial where this device is used for download of APT
satellite weather images with an appropriate antenna.
My next project will be to build a $20 right hand circularly polarized VHF
antenna for download of APT weather images from NOAA and Russian satellites
and mount them on my webpage at the local astronomy club. My long term goal
is to build a GHz radio front end for deep space radio telemetry. My ham
club thinks I am a crazy person and I have been shunned.
The RTL2832U+R820T SDR dongle is a great and inexpensive device and so is
the MK802 IIIs dongle, if you know what you are doing.