Web SDRs & How to use them

6. Web SDRs & How to Use Them

Web SDRs have become increasingly important in recent years, particularly among radio enthusiasts. These web-based receivers allow users to tune into radio signals from across the world and study rare or exotic radio signals in the comfort of their homes. With web SDRs, you can listen to both local and international radio stations, and you can listen to various types of radio transmissions including AM, FM, SSB, and other digital modes.

What are Web SDRs?

Web SDRs are digital radios connected to the internet to provide access to stations globally. Instead of having to physically tune a radio, with a WebSDR, listeners can simply use a web browser to tune in to radio signals from anywhere in the world, as long as they have an internet connection. This technology has opened up new avenues for radio enthusiasts and casual listeners alike to explore different frequencies and waveforms, without the need for specialized equipment or geographical limitations.

Why are Web SDRs important?

Web SDRs are a valuable resource for radio enthusiasts and they offer numerous advantages over traditional radios, making them important for various reasons. Below are some key reasons why web SDRs are important:

  • Cost-Effective Access

Using a web SDR is particularly useful for amateur radio operators who may not have access to expensive radio equipment or who may not have the time or resources to set up an antenna and receiver. With a web SDR, you can listen to a wide range of radio stations without any additional equipment.

  • A multitude of Stations

With web SDRs, listeners can access a plethora of stations worldwide, including those which may not be readily available through traditional radios in their local area. For example, if you live in a certain part of the world where there are no certain types of digital transmissions such as POCSAG, DRM, wefax, or NAVTEX, you can still listen to them and decode from across the globe with a web SDR. Listeners can tune in to local, national, and international stations in different languages, providing exposure to different cultures. This is particularly beneficial for those who are just getting started with amateur radio, as it allows them to get a feel for the various types of transmissions available. Even if you’re a veteran HAM, Web SDRs can serve as a valuable resource for exploring the propagation of your own signals in real time in various parts of the world, and can assist you in making necessary antenna or hardware adjustments

  • Convenience

One of the main advantages of web SDRs is that they are very easy to use. All you need is a computer with access to the Internet and a web browser. They offer the convenience of accessing radio stations anywhere, anytime providing the listener’s freedom to determine what they wish to listen to, regardless of their location. There are many sites where you can find a web SDR, and they are usually free to use. You simply navigate to the website, find the SDR you want to use, and tune in to the station you want to listen to.

How to use Web SDRs

In recent years, the popularity of WebSDR services has skyrocketed, with numerous websites and online platforms offering access to a wide range of radio receivers. Some of the most popular WebSDR services include Spyserver Network, SDR++ Server, KiwiSDR, WebSDR, and GlobalTuners, they are all free to use and do not require any premium subscriptions.

Let’s talk more about KiwiSDR…

KiwiSDR is one of the most popular platforms when it comes to WebSDR services. It has more than 600 SDRs worldwide as of now. Designed and developed by John Seamons (ZL/KF6VO), KiwiSDR has gained immense popularity for its unique capabilities, easy-to-use interface, and ever-growing list of useful extensions. It’s essentially a 14-bit HF SDR with 32MHz of bandwidth coupled with a BeagleBone single-board computer.

Using KiwiSDRs is simple and straightforward. To access a Kiwisdr, simply launch a web browser and open http://kiwisdr.com/public, You will be directed to the user interface, where you can find available Kiwisdr devices. Alternatively, you can click on “KiwiSDR Map” to find receivers in the desired locations.

Once you are in the user interface, select a Kiwisdr device from the available device list. Only four users can use one KiwiSDR at a time, so choose a less busy one for better performance.

The user interface is pretty much self-explanatory, you can either directly input the desired frequency in the frequency text field or select the desired band from the drop-down menu and move the “VFO” indicator to a frequency of interest. It’s possible to monitor two frequencies simultaneously and switch between them by clicking on the “VFO Switch” button. The Spectrum window can be toggled by the “Spec” button but it’s advisable to keep it off for better performance. Additional audio settings, waterfall settings, noise reduction, gain control settings, connected users, and status info toggles can be found just below the waterfall zoom control section. The signal strength of the tuned transmission can be viewed by the “S Meter” field.

Decoding WeFax using KiwiSDR

Assortment of additional extensions are available in the “Extensions” drop-down menu to decode supported digital transmissions such as WSPR, FT8, JT65, CW, WEFAX, DRM, HFDL, SSTV, and NAVTEX. Previously identified digital transmissions are saved as “Flags” above the waterfall window, and clicking on one of them will easily tune to that particular transmission. Then you can choose the corresponding extension from the extensions drop-down menu to decode it. Above is an example of decoding WEFAX signals with the “HF WEFAX Decoder” extension.


Web SDRs have made a significant impact on the amateur radio community by providing an accessible and affordable way for enthusiasts to experiment and explore the radio frequency spectrum. Additionally, they have facilitated the sharing of radio resources among amateur radio communities and provided a virtual meeting place for enthusiasts to collaborate and learn from one another. In summary, the significance of web SDRs for amateur radio cannot be overstated, as they provide an unprecedented opportunity for anyone with a passion for radio to explore the world of radio communication.

Written by Dilusha Samarasekara – Associate Member, RSSL

One thought on "Web SDRs & How to use them"

Leave a Reply

Your email address will not be published. Required fields are marked *