Roundup of Software Defined Radios

New software defined radio (SDR) products are popping up every few months these days so we thought we’d compile a big list of available SDRs.

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Cheap AIS Ship Tracking

Large ships and passenger boats are required to broadcast an identification signal containing position, course, speed, destination, and vessel dimension information to help prevent sea collisions. This system is known as the “Automatic Identification System” or AIS for short. AIS can be decoded with an RTL-SDR dongle and right software.

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RTL-SDR for Budget Radio Astronomy

With the right additional hardware, the RTL-SDR software defined radio can be used as a super cheap radio telescope for radio astronomy experiments such as observing the Hydrogen Line and meteor detection.

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Measuring filter characteristics and antenna VSWR with an RTL-SDR and noise source

By using an RTL-SDR dongle together with a low cost noise source it is possible to measure the response of an RF filter. Also, with an additional piece of hardware called a directional coupler the standing wave ratio (SWR) of antennas can also be measured.

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Receiving NOAA Weather Satellite Images

Everyday multiple NOAA weather satellites pass above you. Each NOAA weather satellite broadcasts an Automatic Picture Transmission (APT) signal, which contains a live weather image of your area. The RTL-SDR dongle combined with a good antenna, SDRSharp and a decoding program can be used to download and display these live images several times a day.

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Review: Airspy vs. SDRplay RSP vs. HackRF

When people consider upgrading from the RTL-SDR, there are three mid priced software defined radios that come to most peoples minds: The Airspy, the SDRplay RSP and the HackRF.  These three are all in the price range of $150 to $300 USD. In this post we will review the three units and compare them against each other on various tests.

 

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List of SDRSharp Plugins

There are a number of SDRSharp plugins that extend its functionality. Here is a collection of all the plugins and download links that we know of.

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JAERO: A RTL-SDR compatible decoder for Inmarsat AERO signals

AERO is a system that provides a L-Band satellite based version of VHF ACARS (Aircraft Communications Addressing and Reporting System). ACARS is typically used by ground control and pilots to send short messages and is also sometimes used for telemetry. With JAERO and an RTL-SDR these signals can be decoded.

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RTL-SDR Direct Sampling Mode

The RTL-SDR software defined radio can be told to run in a mode called “direct sampling mode”, which with a small hardware mod allows the dongle to tune to the HF frequencies where ham radio and many other interesting signals are found. This means that no upconverter circuit is required.

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Decoding Digital Voice (P25, DMR, NXDN, D-STAR) with DSD+

Learn how to decode digital voice communications like APCO P25, DMR MotoTRBO, NXDN and D-STAR with DSD+ and an RTL-SDR dongle.

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Review of the TCXO Modified RTL-SDR Dongle

A few days ago we had a post about a modified RTL-SDR dongle for sale which has the low quality 28.8 MHz oscillator replaced with a high quality 28.8 MHz temperature controlled oscillator.

Nobu Saitou, the creator of these dongles has sent us a sample to review. On the inside of the dongle the 28.8 MHz crystal has been removed, and replaced with a 28.8 MHz temperature controlled oscillator. The desoldering of the old oscillator and soldering of the new TCXO appears to be neatly and professionally done.

TCXO Photo
TCXO RTL-SDR Dongle Photo

After plugging in the dongle and firing up SDR#, we tuned to a known trunking control channel at 152.850 MHz and measured the frequency offset. It turns out that with the TCXO no frequency correction was required at all. I believe that from Nobu’s blog post, this oscillator can have a max deviation of +-2 PPM, which is incredibly small.

TCXO Dongle with Zero PPM correction required
TCXO Dongle with Zero PPM correction required

We compared this result to a standard dongle with the original oscillator and found the frequency offset required to be 44 PPM.

Standard Dongle Frequency Offset
Standard Dongle Frequency Offset

As the dongle heats up from use, the oscillator will experience thermal drift, causing the frequency offset to change. The TCXO should be immune to this problem due to it’s temperature compensation circuitry. To test the temperature compensation, we cooled both a TCXO dongle and a standard dongle down in a refrigerator first to simulate cool climate conditions. We then measured the change in PPM offset after 30 minutes of dongle operation. As expected, the TCXO had almost zero drift after 30 minutes (<<1 PPM), whereas the standard dongle had a drift of about 6-7 PPM (approx. 1 KHz drift).

TCXO Oscillator: Frequency drift after 30 minutes
TCXO Oscillator: Frequency drift after 30 minutes
Standard Oscillator: Frequency drift after 30 minutes
Standard Oscillator: Frequency drift after 30 minutes

The results of this simple test show that the TCXO used in these modified dongles is an accurate and stable frequency source as was expected. If you want one of these dongles they are for sale at the creators Amazon Store (direct link to TCXO product here). Currently it seems that Saitou’s products cannot be sent abroad outside of Japan, but he recommends this agent service for ordering internationally.

Edit: The TCXO can now be bought internationally from 1090mhz.com

10 comments

  1. Pingback: RTL-SDR with Forced Air Cooling - rtl-sdr.com
  2. Brent Harvey

    I’m following a trunked system as well, and believe that its just too much for the original nooElec dongle, when switching from freq. to freq. there seems to be a sudden drift when it shifts, also the stability is intermitting…I run two dongles one for control chan. and the other for voice(dsd) and get about 70% decode rate.. tried to boost the signal and played with RF dB level, but I believe its just the dongle not feeding a clear signal.

  3. soooooil

    Is there a possibility of buying the tcxo chip only?
    I don’t see why the modified dongle should cost $60 while unmodified one costs about $10-15 and the typical tcxo is about $5.

  4. sensei

    Direct link to TCXO product is a broken Google Translate form amazon.jp. Any posibility of buying it from Europe? Could you contact Nobu Saitou about this or provide me his email address?

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