Showing posts sorted by date for query r820t. Sort by relevance Show all posts
Showing posts sorted by date for query r820t. Sort by relevance Show all posts

Calibrating low cost Software Defined Radios like the r820t

  1. Local LTE carriers are carefully frequency corrected.  You will see a quiet spot in the energy right in the center.  Example: 737,000,000 Hz
  2. TV Carriers have a ATSC pilot that is very distinct and easy to tune to.  Examples: 470,309,441 Hz and 174,306,000 Hz

R820T with HDSDR

I went to Radio Club and a few people were interested in the use of the R820T with HDSDR so this post is for them.
  1. Visit and click the download link at the bottom of the page.  Download and install.  
  2. Play around with it using pre recorded I/Q base-band files to decide if this is for you.   
  3. Order:  I have purchased a few of these, the best quality and fastest delivered unit came from I used the ebay store to get free shipping, total cost $17.95.  I also purchased from China seller on ebay same chips, larger package, $8.75 delivered.  Frequency was off by more in the China version but both need to be adjusted in software anyway so it did not make much difference in the end.  While both of the units come with an antenna, you will likely want to attach your own, so you will need MCX Male adapter or connectors.  My favorite wide band RX only antenna is the amplified TV antenna that is already plumbed in every room of the house. For that I purchased 6in F female jack to MCX right angle male Jumper pigtail RG316 cable
  4. Once the unit arrives, do not install the software that comes with it.  Follow these instructions to get it going.

Other links you might like:
  2. My other posts on R820T
  7. SDR# Demo by Clayton Smith VE3IRR
  14. ModeSDeco2

Rafael Micro R820T tuner as USB SDR source for hold music in asterisk PBX

So you want to play a local radio station, HAM repeater or other radio source 24MHz-1700MHz as hold music in asterisk. $8-$18 buys you the USB radio, antenna and all depending on source. Here is how you do it.

# Install git and libusb
$ sudo apt-get install git-core libusb-1.0-0-dev

# Change to your build directory
$ cd /usr/src/

# Download the source
$ git clone git://

# Build with autotools
$ cd rtl-sdr/
$ autoreconf -i
$ ./configure
$ make
$ sudo make install
$ sudo ldconfig

# In order to be able to use the dongle as a non-root user, you may install the appropriate udev rules file by calling
$ sudo make install-udev-rules

# Plug in the USB radio, and check if it is detected
$ lsusb
Bus 001 Device 008: ID 0bda:2838 Realtek Semiconductor Corp.

#Test by playing FM 91.1MHz to local speaker
$ rtl_fm -f 91.1M -W -r 32k - | aplay -r 32k -f S16_LE

# Update your Asterisk Music On Hold config
$ vi /etc/asterisk/musiconhold.conf

application=/usr/local/bin/rtl_fm -f 91.1M -W -r 8k -

# Restart
/etc/init.d/asterisk restart

Software Defined Radio

I am getting a $18 RX only Software Defined Radio but expect to be able to do many of the same things as in this b200 video with the cool GNURadio software.
4 Jan 2014 $8.75  rtl_fm -f 96.3e6 -W -s 200000 -r 48000 - | aplay -r 48k -f S16_LE