Welcome to CATSync

V1.30 – Now with Open Web RX support

CATSync Logo

The CAT Tool for WebSDRs

CATSync allows you to synchronize public WebSDR receivers with your real rig connected via CAT control to your computer. It supports the classical WebSDR, Kiwi SDR as well as Open Web RX:

  • Control any public WebSDR server by means of your real RIG…
  • Supports a wide number of RIG’s (it uses the popular OmniRig engine)
  • Supports WebSDR, KiwiSDR and Open Web RX browser-based SDR receivers
  • Tune the VFO of your radio and see the web SDR follow in realtime !
  • Click on the WebSDR waterfall and retune your rig in realtime.
  • Synchronizes both, frequency and mode changes (CW, USB, LSB, AM, FM)
  • Listen to the same frequency as your rig via web SDR or vice-versa
  • Ideally suited e.g. for people suffering from local QRM or working in nets
  • Can track RX or TX VFO (e.g. to find that split of a DX station) if radio CAT command set of your rig supports both independently
  • Can be interfaced with popular logging software using OminRig or via VSPE port splitter.

This software can help you to bring you back into ham radio when you are suffering from local temporary or permanent high noise levels in an urban QTH location.

You can download a functional Demo from these links:

Important Note:
When installing this software you may get a warning by your Windows Security System saying that this application is from an “Unknown Publisher” and therefore recommends not to install it, as it may be a malicious program.

See my blog post in this regard:
Are my installers secure?

Download Sites:

Download CATSync Demo V1.22 Installer here (Dropbox)

Download CATSync Demo V1.22 Installer here (GoogleDrive)

NEW ! CATsync QO-100 Edition

Note: If my demo app crashes on startup, please install Microsoft Visual C++ 2013 x86 redistributable runtime files (see system requirements below)
Make sure it’s really x86 and not x64 (even on 64bit Windows systems !!!).

The demo has all the functions of the full version, with the exception that it will not retune the web SDR audio in realtime (you only see the web SDR frequency updating, but the audio remains on the former frequency). You can only retune the audio to the new frequency manually. The new Click + Tune feature is limited by 90 seconds per session.

If the demo works on your system and you like the software please consider getting the full version.  The full version is tuning both frequency and audio synchronized in realtime and now even bidirectionally!

Press the “Buy Now” button below. This will guide you to my webshop system and allows you to pay by PayPal.
The V1.30 Full version costs 9.95€.
You do not need to have a PayPal account, you can pay as a guest at PayPal:

Buy Now Button with Credit Cards

In case of difficulties please contact me directly under the e-mail address provided by PayPal in the payment receipt sent to you by e-mail. For future updates you will be automatically notified to the e-mail address you used for purchasing.


Microsoft .NET runtime libraries 4.62 or later must be installed (from the Microsoft site)
Microsoft Visual C++ 2013 (x32 version) redistributables must be installed (from the Microsoft site) up to V 1.22
OmniRig CAT software must be installed (Freeware from DX Atlas site)
Many ham shack PC’s already have those components installed, since much other third-party software make also use of them.

CATSync supports up to two switchable radios connected via two separate serial ports.
The program is very easy and intuitive to use. Try the demo and see for yourself.

This application tunes the web SDR in realtime, however, given the way how a web SDR works there may be a light latency between your real rig and the WebSDR audio due to the waterfall and audio transmission and codec decompression time required to travel from the SDR host server to your PC speakers.

Please note that not all radios support separate control of RX and TX VFO via CAT. Some radios only allow control of the currently active VFO. (e.g. my TS590 does support it, while my IC7300 doesn’t)

See demo video of CATSync V1.10 in action with my Kenwood TS590:

Version History

NOTE:  Users of V1.2x versions continue to receive free critical bugfix versions when they become available.
Upgrades from V 1.2x to V1.3 are not covered by free upgrades anymore and need to purchase a new license
01 JAN 2023 V1.30
– New feature: Now supporting Open Web RX web SDR servers (next to WebSDR and KiwiSDR systems)
   Limitation: Open Web RX requires the listener to select the right SDR “band” manually
   (this is a limitation within the Open Web RX system – not CATsync)
– Update to the newest Chromium web browser engine
– Visual C++ 2015-2022 x86 runtime files are now required and supplied/installed by the CATsync installer package
– Favorites editor now saves renamed entries correctly
– Support for “non-standard” 1Hz display resolution (used by some US websdr servers running modified websdr code)
– Updated K3 CAT emulator, now also allows mode control in addition to frequency control.
04 JAN 2020 V1.22
– New feature to support also keyboard tuning (a feature that is built-in on most WebSDR, but not on KiwiSDR)
– Top menu bar is now collapsible. You can make it disappear by dragging the divider line up and down
– New feature to allow offset tuning by a few +/- 5 kHz to synchronize your radio with the remote web RX
– Favorites window now allows renaming, deleting and sorting the order
– The CAT Radio Emulator for external software had some bugfixes for hamlib polling (supports only frequency setting).
– Fixed a problem that CATsync would unmute (mute on TX feature) while Windows was already muted before
20 JAN 2019 V1.21
– Fixed the broken JavaScript injection preventing KiwiSDR with newest firmware to react on “Click&Tune” – works now OK.
– Fixed flickering database labels while retuning.
– Introduced Browser Zoom with CTRL + and CTRL – hotkeys (same as normal browsers use)
– Saving of audio recordings may not be working properly due to limited access rights to Windows default application install path.   Now a “Save as” file dialog is shown with your Windows documents folders shown before saving, which should give       you full flexibility
19 JAN 2019 V1.20
– Fixed one major bug breaking the link to the SDR website after loading a second site
– New Feature: CAT Radio Emulator. This allows CATsync to behave like an external radio. Elecraft K3 is being emulated.
(e.g. this way you can connect e.g. external programs like WSJT-X or FLDIGI or others to the emulated K3 radio in CATsync)
This new feature may still be buggy with some untested programs and CAT emulator supports only frequency but not mode setting (yet).  To use this feature you need to install a third-party virtual serial port driver.
– Browser cookies are now supported, allowing memorizing e.g. last frequency, mode, memories, etc.
– Mouse wheel tuning in WebSDR is now also syncing CAT
(KiwiSDR does not support mousewheel tuning as it uses it for zooming)
– Audio recording function in WebSDR and Kiwi now working. Audio file is saved into CATsync application path.
– RX / TX switching of your local radio can be now also controlled via CATsync GUI button.
– Introduced unmute delay (200ms for WebSDR and 1500ms for Kiwi) for “Mute on TX” function
in order to reduce hearing your own echo at end of TX.
– Various smaller bugfixes (based on user reports)
24 SEP 2018 V1.12
– New fixed rendering support for Windows 10 High-DPI (4K) displays with enabled screen zoom
– Fixed KiwiSDR mode change (was broken after KiwiSDR firmware update of 7th July 2018)
– New support for clicking on Kiwi SDR station database labels (it will switch frequency and mode)
Important: This new feature requires a KiwiSDR with firmware v1.231 or later
– Update radio via CAT when manually entering a frequency and hit enter (on WebSDR and KiwiSDR).
06 MAY 2018 V1.11
– Fixes a decimal frequency conversion issue depending on different country settings of your Windows system
(was affecting the new “Click + Tune” feature)
05 MAY 2018 V1.10
– Revolutionary new ” Click + Tune” panadapter-like feature for bidirectional control Rig – WebSDR – Rig
– Future updates (after 1.1) will automatically remember all user settings and bookmarks from previous versions
– minor code cleanup
09 APR 2018 V1.04
– Minor code optimizations
– Better user error handling for a more robust Favorites feature
– Favorite names are now stored correctly if the user changes the name
– Added explanatory tooltips to some controls when moving the mouse over them
– Added feature to turn CAT synchronization on / off while CATSync is running
– Improved again the internal Kiwi SDR detection algorithm
(some Kiwi’s were not be reliably detected, if they run a modified server software)
4 APR 2018 V1.03
– Minor bugfixes
– Moved from using config.cfg file to internal .NET app settings XML file
– Added a Favorites feature to store your own Web SDR links (including private non-public ones)
– Removed the two WebSDR and Kiwi SDR list shortcut buttons
(the two links are provided now as pre-programmed favorites)
27 MAR 2018 V1.02
– Minor bugfixes
– “Mute audio on TX” does no longer block Windows mute if Rig sends continous RX/TX status bytes via CAT
– Update frequency / mode on newly loaded web sdr website
– Improved algorithm to detect type of websdr for better responsiveness
– Added “type of WebSDR” status message below Load button
25 MAR 2018 V1.01
– Few minor bug fixes (“Buy Full Version” button in Demo now uses an external browser)
– New “Mute audio on TX” function  (if CAT of your radio supports RX / TX status)
– Remembers last Window size and position
17 MAR 2018  V1.0
– First release version