Nothern Utah WebSDR Logo - A skep with a Yagi Northern Utah WebSDR
Receiving equipment and software

What is here

This page discusses both hardware and software used at the Northern Utah WebSDR as well as SDR-related topics.

In the first section we talk about the hardware - and some of the software - used at the Northern Utah WebSDR with topics ranging from the receive hardware itself, RF filtering, limitations of different types of hardware, and how to make hardware with limited capability (e.g. the RTL-SDR) work as well as it possibly can at HF.

In the second section we discuss other means of getting signals into the PA3FWM WebSDR software that provide high performance and wider bandwidth than would otherwise be possible.  Specifically, the use of the SDRPlay receivers and how we can process signals and input them to the WebSDR.  Additionally, we touch on alternate (open-source) drivers that can be used with the SDRPlay hardware as well as how one can leverage other software (e.g. "csdr") to cover more than one amateur band with a single SDRPlay receiver.

In the third section we discuss the ka9q-radio package.  This extremely powerful package - almost unknown to the amateur computer at the time of this writing - allows the creation of many (hundreds!) of virtual receivers across a very wide bandwidth (an entire VHF or UHF band - or even the entire HF spectrum) with modest hardware - no GPU required.  We expect that the principles used in ka9q-radio will, in the future, find wider adoption once its utility is discovered and understood - these both being reasons why these pages exist.

Hardware and software at the Northern Utah WebSDR

A number of different types of receive gear is and has been used at the Northern Utah WebSDR and the job of this equipment is to take off-the-air RF signals and present them to the WebSDR servers in an appropriate format.  Because of the wide signal dynamics present when receive signals off the air, consideration must be given to these varying conditions in terms of filtering, signal level adjustment, and the choice of the gear itself - all while being aware of the limitations of this gear and accommodating it as much as is practical.

The articles below reflect the use of different types of gear over the years that the Northern Utah WebSDR is in operation.  Some of the gear described below has been depracated/replaced with something more modern or capable - usually to acheive greater frequency coverage with a single receiver - but the discussions of the designs and techniques are still relevant.

Higher sample rates on the WebSDR's 16 bit Signal path:

Recently (as of November, 2021) we have switched many of our receivers to higher-bandwidth 16 bit receivers, allowing us to cover most of the HF bands (160-12 meters) with a single receiver instance, rather than having to split an amateur band according to the 192 kHz limit of typical sound cards (e.g. 3 receivers for 80, 2 each for 40 and 20, etc.)  This takes advantage of the fact the the PA3FWM WebSDR server can, in fact, be used at 384 and 768 kHz to cover more spectrum on a single "band".

We are doing this with patched drivers and custom code to allow the interfacing of the SDRPlay RSP1a receiver into the Linux ALSA sound system, but this could, in theory, be used with any hardware that is capable of producing a 384 or 768 kHz raw I/Q stream.

We are in the process of documenting this "upgrade" and the following article(s) are available:

Pages about KA9Q-Radio

KA9Q-Radio a software suite that is capable of processing large amounts of raw reciever data efficiently in a manner quite different from your typical "SDR" program.  This is Linux (only) software with no GUI, intended primarly to be the "front end" of a system that is capable of handling 10s of MHz of bandwidth simultaneously (with no GPUs!) and hundreds of individual receive channels.


For more information, see:

Notes about installing the PA3FWM WebSDR software on Ubuntu 22.04

The page, "Installing a WebSDR on Ubuntu 22.04 (notes)" (link)contains information about setting up a WebSDR on Ubuntu 22.04.  While some of this information is specific to the custom configuration at the Northern Utah WebSDR, it may be of use for "out of the box" and simple configurations.  It may be particularly helpful with respect to the installation of dependencies of the WebSDR binary that have since been deprecated.

Additional information:
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