Category: News

Airspy Competition Winners Announced

Last week the Airpsy team gave us the opportunity to give away some prizes, so we started a comment competition. The prizes were an Airspy R2 + SpyVerter, Airspy Mini + SpyVerter and SpyVerter. The competition closed yesterday with over 500 entries, and the winners have now been selected via Congratulations to the winners below:

Larry (Airspy R2 + SV)
If I am going to win something from this one stuff, me build internet remote receiver on hill in central Europe (CZ) for all readers and fans of website, generally for all RTL SDR enthusiasts….. :-)))
Pour Felicitér 2017
Larry (Ladislav)

kevin (Airspy Mini + SV)
been a ham a couple years now. their are so many uses for sdr’s ! it’s so cool. just looking down the list of others comments, i was like ‘oh ya’ forgot about that idea. awhile back we did a demo at our ham club with a el cheapo sdr and it sparked some interest , would like to play around with some of the newest toys, worlds of diff in capabilities. ultimate goal is to find the right one for the clubs emergency trailer. seeing the bands and whats going on, is priceless :)

Josh (SpyVerter)
I’d love to finally get into the HF band!

If you’re a winner please check your email address for the competition winner email.

The competition produced some very interesting comments that show the diversity in projects that can be performed with a SDR receiver and we strongly encourage you to read through the comments if you are looking for project ideas.

If you didn’t win, sorry! Better luck next time. But please continue to follow us on Facebook and Twitter as we will have more competitions and more prizes to give away later in 2017!

HDSDR Version 2.75 (Stable) Released

The beta 2.75 version of HDSDR was released about two months ago. Now the stable version has just been released. HDSDR is a free general purpose SDR receiver, similar in nature to other programs like SDR# and SDR-Console. HDSDR can be downloaded from

The author of HDSDR emailed us with the following release information:

this morning we released the final version 2.75. Here’s the changelog:

Version 2.75 (January 01, 2017)
– more recording options
– support for 8bit sampling format – ideal for RTLSDR, halving RF recording size
– display level / clipping for RF and AF
– additive noise generator for hiding aliases
– Highpass Filter for AM/FM deactivatable – useful for slow digimodes
– configurable gain for I/Q output – useful for digimode decoding weak signals of SDRs with >16 Bit dynamic range
– Uniform “Calibration” dialog for Frequency/S-Meter/DC Removal/Channel Skew
– “Custom color palette” to customize colors of Waterfall/Spectrum and some more
– output soundcard no longer necessary (e.g. for recording or monitoring)
– support for 8k display resolution (7680×4320)
– some new keyboard shortcuts (see )
– extended ExtIO capabilities
– experimental transmit capability through ExtIO API interface
– many fixes and improvements

Some of the new features were introduced especially for the RTLSDR Dongles:

– 8 bit support, of course

– displaying the RF (ADC) level in dBFS allow working with deactivated Tuner AGC – NOT oversteering/clipping the ADC.
This would also ease making good suitable recordings as used in

Especially for decoding this kind of signals (AM/FM) , deactivating the Highpass filter (Ctrl-H) will make the demodulated Audio clearer:
long periods of positive or negative levels will not fade towards zero.
Find attached recordings and screenshots with active and deactivated highpass filter of a garage door opener demodulated in AM.

– additive noise generator (Ctrl-N) is for hiding some alias carriers in scenarios where the ADC does not see real noise from the antenna.
The noise generators level has to be configured carefully for not hiding real signals. A level between -25 to -10 looked fine for me. But that should be measured in a lab.

Below are the mentioned attached images and .wav files.

Highpass Filter - Active
Highpass Filter – Active
Highpass Filter - Inactive
Highpass Filter – Inactive

Highpass Active .wav file (Download)

Highpass Inactive .wav file (Download)

Airspy Mini Christmas Sale – $80 USD

The Airspy Mini is a software defined radio with a tuning range of 24 MHz to 1800 MHz, 12-bit ADC and up to 6 MHz of bandwidth. It usually costs $99 USD and is the younger brother of the $149 USD Airspy R2.

Currently the manufacturer iTead is running a Christmas sale on the Airspy Mini. The sale price is $80 USD, which is a 19% saving. To get the sale price you need to click on the “Get coupon code here” link and then share the promotion to your Facebook, Twitter or LinkedIn account.

Update: They have given us a special blog coupon code “AS-RTLSDR-BLOG“. Just use this code at the checkout and it will apply the discount without the need to share. Edit: The blog coupon appears to have stopped working, an alternative one that is still working is “as3“.

The sale lasts from December 20, 2016 – January 3, 2017.

If you want to see more about the Airspy Mini then see our review here. Our other previous review comparing the Airspy R2 against the SDRplay RSP and HackRF may also be of interest as the Mini’s performance is very similar to the R2.

The Airspy Mini iTead Christmas Sale
The Airspy Mini iTead Christmas Sale

New Linux RTL-SDR Driver with Fully Exposed Controls

A new Linux based driver for the RTL-SDR has been released by Milen Rangelov (aka gat3way) which exposes all the adjustable settings on the R820T/2 tuner chips. This exposes adjustable sliders for settings like preselection, IF and notch filters and the multiple gain stages on the R820T/2. In the standard drivers the filters and gain settings are mostly set automatically, but manually adjusting them could yield better results. The filters are not very strong, but they could be used to help block out an interfering signal, increasing the dynamic range of the RTL-SDR.

Over on his post at r/rtlsdr Milen wrote the following about his driver:

The idea in brief is to modify the librtlsdr code so that an unix domain socket server receives i2c register set/get commands and executes them. It only works for r820t tuners. This modified rtlsdr library is then dynamically preloaded by means of LD_PRELOAD and used by the SDR software. This is actually what happens when you call r820tweak <program>. This way, no modifications to both gr-osmosdr source and the SDR program are required, instead of waiting for them to implement those controls, we kind of have a separate program that tweaks them.

The GUI program is a simple wxpython client, it currently exposes the following settings:

LNA, Mixer, VGA gain stages – the 3 variable gain stages

LPF/HPF filter cutoff – these control the “width” of the r820t2 lowpass/highpass filters, those filters are relatively sharp and this in turn is very useful to increase the dynamic range by fitlering out strong signals “close” to the weak signal you are hunting. Those are among the nicest features to play with, together with the gain stages.

LPNF cutoff – apparently there is also a low pass notch filter, however this doesn’t work as I expected. Anyway, still useful as a kind of variable attenuator.

Filter bandwidth – there is a bandpass filter which isn’t quite “sharp” at all, centered at the center frequency. Kind of additional filter, easier to manipulate than the rest of them, but not that powerful. May provide some extra dynamic range. Behaves kind of weird when gqrx decimation is used.

As far as the gain stages are concerned – the LNA gain is the first stage and thus the most important – it determines the SNR. Mixer gain is less important (unless the signal is too weak). The VGA gain should be almost always set to zero as it doesn’t contribute to the SNR at all while keeping the dongle warmer and so more thermal noise.

In the R820T2 i2c register specs there are some other interesting features, currently unexposed. One of them is the band selection filter (lo/med/high) which apparently is even used in the librtlsdr driver. I found changing that has absolutely no effect for me unfortunately. It might have provided opportunities for better reception around the “verge” where the librtlsdr driver switches them (approx. at 310MHz and 588MHz). But switching them has absolutely no effect.

The new fully adjustable driver by gat3way.
The new fully adjustable driver by gat3way running in GQRX. V3 Stock Availability and Holiday Shipping Times

This is just an update post for those wishing to purchase or are waiting on delivery for items from our store at

Amazon USA

The V3 has proven to be more popular than we anticipated and Amazon ran out of stock a few weeks ago. New stock should be arriving at the Amazon warehouses early next week, but we don’t know how long Amazon will take to process the stock and put it back on the shelves. It should hopefully be ready in under a week.


For international orders from our Chinese warehouse, please be aware that international shipping is quite slow at the moment, due to the peak season parcel rush. The international mail system struggles to cope with mail at this time of the year due to a vast increase in Christmas parcel volume. Delivery times are still typically under 4 weeks but for some parcels, and to some countries we can expect shipping times of up to 6 weeks or longer. 

Some people have noted that parcels ordered after a previous order have arrived earlier. We use the same postal system as everyone else (there’s only really one international air mail system!), but what can happen is that on some days the parcels may get a direct flight, and on other days they may get an indirect flight. Those indirect ones can end up taking much longer. Also planes can break down, parcels can miss a connecting flight or security can hold a container of many parcels for days just because they saw one suspicious parcel inside. Thus international parcel delivery times have a very large scattering, ranging from less than a week to six weeks or more. We thank you for your patience if your parcel happens to end up on the slower end of the scale. But if your parcel does end up taking over 6 weeks please let us know as we may be able to open a lost parcel investigation. If your parcel is lost it will be resent or refunded on your preference.

If you are tracking a parcel we recommend, and Try all three as sometimes one has more up to date tracking than another. Please note that we’ve found that around this time postal workers will often not bother to scan the tracking label on parcels, since they are rushing so much. This can cause a lack of tracking updates for a while. Also if there are queues for customs checks in your local country the parcel can wait around in the container without a scan for a long time, until customs gets to it.

We have several shipping methods available. China Post/Swiss Post/HK Post are about the same speed once they leave. But generally Swiss/HK post are faster to leave China. China Post parcels can sometimes take a few extra days to pass through security. Some countries which support it, will automatically be upgraded to EMS ePacket priority mail. We also have some new special methods for some countries which are still air mail, but use a faster more direct flight to the destination. Of course the more expensive express mail services like DHL/UPS/Aramex are also available, but even they have about a 1 week shipping delay at the moment.

However, despite these shipping time uncertainties, the majority of parcels still seem to be making it through the postal system in a timely manner. Thanks to everyone for supporting the blog!

R820T2 Register Description Data Sheet Now Available

Recently Luigi Tarenga wanted to do some work on developing RTL-SDR drivers, so he emailed Rafael Micro requesting some additional documentation about the chip. Usually previous requests to Rafael Micro for such information seem to have gone unanswered, but this time it seems they have decided to publicly released the Register description document for the R820T2 chip.

Previously the R820T datasheet was leaked/released to the public, but the information in the datasheet did not help much with driver development. This register description document describes the function and configuration bits for the registers on the chip, and may be useful for people wanting to develop better drivers for the RTL-SDR.

We have uploaded a copy on our server here.

Description of some of the registers in the R820T2 chip.
Description of some of the registers in the R820T2 chip.

The 2016 /r/rtlsdr Reddit Giveaway

The mods of the /r/RTL-SDR community on the Reddit discussion platform are currently hosting an RTL-SDR themed giveaway. The prizes up for grabs include units which have been donated from ThumbNet ( and us at The prizes also include several donated home brew projects including filters and downconverters. See the table at the end of this post for the full prize list.

To enter all you need to do is write a comment on the competition thread at and mention what you like about SDR and what you hope to do with a prize if you win. While you’re at it we strongly suggest subscribing to /r/rtlsdr if you haven’t already as that is one of the the largest and most active communities of rtlsdr users on the web.

The competition closes on December 3rd and only one entry per household is allowed.

Place Prizes Description
1st-2nd 2 ThumbNet – N3 SDR RECEIVER
3rd-5th 3 RTL-SDR Blog V3 Dongle + Antenna Kit
6th-7th 2 $25 ThumbNet – Gift Certificate
8th-11th 4 Blog V3 Dongle Only
12th 1 PA0RDT Mini-Whip Antenna
13th-14th 2 Blog Broadcast FM Filter
15th-16th 2 Up to ~4.5GHz Microwave Downconverter
17th 1 70cm HamSat / 433 Combline BPF
18th-20th 3 Choice of Custom Made 5 Pole HF BPF/LPF/HPF

New Low Power RTL-SDR’s for Stratux ADS-B Receivers

Stratux is an RTL-SDR based project that gives small plane pilots access to ADS-B data, without having to purchase an expensive commercial ADS-B installation. It consists of software that runs on a Raspberry Pi, and two RTL-SDR dongles to receive both 1090 MHZ ADS-B, and 978 MHz UAT. The decoded data is then streamed via WiFi to a tablet running navigation aide software with charts for pilots.

Typically Stratux kits come with two standard ‘Nano’ styled RTL-SDR dongles. However, users of the Stratux system have been reporting problems with overheating, and with the Pi struggling with the high current demands of a typical setup which includes two RTL-SDR dongles, active WiFi broadcasting, a GPS unit and an optional cooling fan. A typical RTL-SDR dongle draws 280 mA, so two dongles are already pulling 560 mA.

Chris, creator of the Stratux software and seller of Stratux kits has just released a new low power RTL-SDR dongle (kit with antennas). The cost is $35 USD for two dongles (one for 1090 MHz and one for 978 MHz). The dongle obtains its low power feature by using a switching regulator instead of a linear regulator as the main 3.3V power regulator on the PCB. Normally you would not want to use switching regulator for the main regulator in an RF device because they are very noisy in terms of RF interference generated. However switching regulators are much more efficient compared to linear regulators, and thus save a lot of current wastage. Other dongle manufacturers like ThumbNet have actually gone the other way, removing the secondary 1.2V switching regulator from the standard dongle design, and using a linear regulator instead. The ThumbNets end up with lower noise, but draw 400 mA of current. 

With the switching regulator the new Stratux dongles only draw about 185 mA, a saving of almost 100 mA. They also generate 0.5W less heat. Users of the Stratux system have so far been impressed with them and have not noticed any appreciable difference in ADS-B performance. We think that these low power dongles might also be of interest to people using them on mobile phones or battery/solar powered remote installations.

The new Stratux low power RTL-SDR dongles.
The new Stratux low power RTL-SDR dongles.

During testing, Chris found that there was no significant noise floor increase visible on the 978 MHz  & 1090 MHz frequencies. Most of the switching noise increase appears to be on the lower frequencies, but those frequencies are not relevant for the Stratux use case anyway.

Chris was kind enough to send us some samples of the new low power dongles. First we ran a noise floor scan with rtl_power to determine the effect of the switching regulator. The results show that the spurs and noise floor readings have definitely increased by a significant amount, with an especially large noise floor rise below 400 MHz. In SDR# wandering switching noise spurs are also visible throughout the spectrum, but they tend to weaken in strength once an antenna is connected.

Stratux vs Standard Dongle vs V3 Dongle Noise Floor Scan
Stratux vs Standard Dongle vs V3 Dongle Noise Floor Scan

Fortunately, ADS-B is very tolerant to spurs and is generally not affected by this type of noise. We’ve only given the Stratux a quick test on ADS-B so far, but when compared against another ‘nano’ styled dongle the Stratux performed nearly identically (in fact even a little better) in terms of messages received. The two dongles were connected to the same antenna via a splitter and we logged the number of messages received in 10 minutes.

Quick ADS-B Reception Test
Quick ADS-B Reception Test

In conclusion the Stratux RTL-SDR set out to solve the mobile power issues suffered by people using the Stratux system. It has achieved that with an over 100mA saving in current use. The new Stratux dongle is much noisier, but the noise does not appear to significantly affect ADS-B reception as seen by our results and from the reports from Stratux users who beta tested this dongle.

Chris has also created a post on Reddit /r/stratux which talks a bit more about the new dongle.