Category: Airspy

RTL-SDR vs. Airspy on ADS-B Reception

With the recent release of ADSBSpy, an ADS-B decoder for the Airspy software defined radio, many people have been wondering how much better the Airspy is compared to the low cost RTL-SDR dongle at ADS-B reception. Over on his blog, Anthony Stirk has performed a test comparing an E4000 RTL-SDR with the Airspy.

In his test Anthony uses an A3 ADS-B antenna from Jetvision.de, and a HABAMP which is an LNA plus 1090 MHZ SAW filter. To create a fair test he used an antenna splitter and measured the reception of both dongles at the same time. He ran one instance of ADSB# for the E4000 RTL-SDR, and one instance of ADSBSpy for the Airspy over 24 hours and recorded the results.

Airspy vs E4000 RTL-SDR
Airspy vs E4000 RTL-SDR

The results showed that the Airspy had approximately 50 km more range compared to the E4000 in some areas. More interestingly the stats showed that the Airspy received approximately 7 million more ADS-B messages compared to the RTL-SDR.

While there is no doubt the Airspy will perform better, one thing to note about this test is that it used an E4000 RTL-SDR which is widely considered to have inferior performance at the 1090 MHz ADS-B frequency when compared to the R820T/2 dongles.

Airspy vs. E4000 RTL-SDR
Airspy vs. E4000 RTL-SDR

New ADS-B Decoder for the Airspy Released

Youssef, the main programmer of SDR# and creator of the Airspy software defined radio has just released a beta version of an ADS-B decoder for the Airspy. The software is called “ADSB Spy” and is similar in operation to ADSB# which is used with the RTL-SDR dongle. The increased sensitivity and lower noise floor of the Airspy should help ADS-B enthusiasts get longer ranges and more aircraft on their screen.

The beta version of ADSB Spy can be downloaded at http://www.airspy.com/downloads/adsbspy.zip.

ADSB Spy - An ADS-B decoder for the Airspy
ADSB Spy – An ADS-B decoder for the Airspy

Spyverter Sneak Preview

The Spyverter is being developed by the creators of the Airspy software defined radio to be a high performance upconverter. It is designed for use with the Airspy, but may also be compatible with other SDR devices too.

Compared to most other upconverters which use a diode ring mixer architecture, the Spyverter uses a different, as of yet undisclosed architecture. The main claimed advantages over other upconverters will be it’s low loss and high IIP3 performance, which means that the Spyverter will not saturate in the presence of strong signals as easily as other upconverters.

Recently a photo of a Spyverter alpha board was released, indicating that the Spyverter is getting close to release.

The Spyverter Alpha
The Spyverter Alpha

Also, a few months ago W9RAN posted a YouTube video about a prototype HF upconverter for the Airspy and we believe he was using an early version of the Spyverter.

Airspy HF Converter Sneak Peek by W9RAN

New Airspy Review from Radio User Magazine

Update: Note that we also now have our own comprehensive review available here which compares the Airspy, SDRplay RSP and HackRF.

A new review of the Airspy (store) software defined radio has been published by Mike Richards in the March 2015 edition of the Radio User magazine. Although the magazine is for sale, the publishers have allowed the Airspy team to release the review for free. The review goes over the Airspy architecture, features, use of the software and presents a favourable tone towards the Airspy.

The Airspy is an software defined radio that costs $199 USD and comes with a 24 – 1800 MHz tuning range, 10 MHz of bandwidth and 12-bit ADC.

Previously Mike Richards also reviewed the SDRPlay, a competitor to the Airspy in Radio User and that review is also available for download.

Airspy diagram from the Radio User magzine review.
Airspy diagram from the Radio User magzine review.

Comparing the Ham-It-Up Upconverter with the SV1AFN Upconverter

Over on YouTube user Mile Kokotov has uploaded a video showing a comparison between the ham-it-up and SV1AFN upconverters. An upconverter allows reception of VLF to HF signals with SDR dongles such as the Airpsy and RTL-SDR.

Mile shows that both the ham-it-up and SV1AFN upconverters use the same core component, a double balanced mixer ADE-1. However, the ham-it-up comes with the option for a noise circuit to be populated. A noise circuit is useful if you want to measure the response of a filter or antenna for example. With the ham-it-up the noise source components are sold seperately and need to be carefully soldered on.

On the other hand the SV1AFN upconverter comes with a built in selectable LNA and better filtering circuitry. The SV1AFN upconverter also uses the ADE-1 in a slightly different design compared to the ham-it-up which allows for much improved performance at VLF frequencies.

In the results Mile uses his Airspy and shows that the SV1AFN upconverter is significantly better at receiving VLF frequencies, and also better at receiving a 28.205 MHz beacon. The results are summarized in the table captured from the video shown in the image below. In the second video Mile also compares the local oscillator drift of each upconverter.

Upconverter comparison results.
Upconverter comparison results screencap.
RF Upconverters Comparison: Ham it Up vs SV1AFN - part1

Airspy Reception Tips and Tricks: Receiving Weak Signals with Strong Nearby Signals

Over on YouTube user Mile Kokotov has uploaded a video showing how he optimizes reception of weak signals in the presence of strong signals on the Airspy software defined radio. He writes:

Using Airspy SDR, I find the interesting way to improve SNR (Signal to Noise Ratio) of the receiving signal, especially in case when very weak signal, which is signal of interest, is close to strong unwanted signals making nonlinear distortion in the receiver front end.

There are two cases:

1. If the weak signal frequency is higher than strong unwanted signals, than you can place the weak signal to the left edge of spectrum window, just before the receiving signal levels goes down to the left. Then you can increase the IF-Gain, Mix-Gain and LNA-Gain so you can improve SNR of weak signal without getting nonlinear distortion from the strong signals with lower frequency.

2. If the weak signal frequency is lower than strong unwanted signals, than you can place the weak signal to the right edge of spectrum window, just before the receiving signal levels goes down to the right. Then you can increase the IF-Gain, Mix-Gain and LNA-Gain so you can improve SNR of weak signal without getting nonlinear distortion from the strong signals with higher frequency.

Of course, the best possible way to improve SNR in wide-band receivers sach is Airspy, Funcube, RTL-SDR and others, is by using narrow filter before Airspy front end, but you will loose wide-band possibilities in that way…

The Wide Dynamic range LNA at the antenna side is strongly recommended for VHF/UHF !

AIRSPY SDR - Tips & Tricks Receiving Weak signals with Strong ones near by

Airspy Direct Digital Converter (DDC) Modification

The Airspy software defined radio comes with breakout pins that connect directly to the analogue to digital converter (ADC) inputs. By connecting an antenna to these inputs together with experimental software it is possible to receive frequencies between 0 – 10 MHz. This is the same trick used in the RTL-SDR direct sampling mod. However, to get decent reception and to keep the Airspy circuitry safe, a low pass filter and isolation transformer are required.

Over on YouTube W9RAN discusses this mod in his latest YouTube video.

Airspy GNU Radio Script for Receiving LRPT Meteor-M2 Weather Satellite Images

Previously we posted about receiving LRPT weather satellite images from the Russian Meteor-M2 weather satellite using the RTL-SDR. Now on GitHub, developer otti-soft has uploaded a LRPT decoder GNU Radio script for the Airspy. The script appears to be a modified version of the GNU Radio based real time decoder for the RTL-SDR, but optimized for the Airpsy and it’s 10 MSPS or 2.5 MSPS sampling rates. Note that although this is a real time receiver, the final image still needs to be processed on a Windows PC using LRPToffLineDecoder.

Also over on Twitter otti-soft has been uploading some images that he has received with his Airspy.

Real time LRPT Receiver for the Airspt
Real time LRPT Receiver for the Airspy