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Pricing and specifications subject to change without notice.

LP-Bridge Software for K3
(for other rigs, visit the LPB2 page)

Warning: LP-Bridge is not compatible with newer versions of HRD because HRD now uses Unicode (32-bit) character encoding for text fields. AFAIK, this problem only exists with HRD, and only with newer versions. We plan to support the newer version when we can get to it, but other things currently have a higher priority.


LP-Bridge provides several main functions... to link the SDR software to the K3 for interactive control, to allow multiple applications to talk to the K3 at the same time and the ability to provide frequency data to external hardware. Throughout this page, the term "SDR software" refers to the NaP3 program written by Pete, F5VNB, PowerSDR/IF v1.19.3.5 by WU2X,  or TRX-Pan for LP-Bridge, written by F6DEX with modifications by N8LP. The first two programs are built upon the open source FlexRadio Systems PowerSDRTM software and are supported by their respective authors, not FlexRadio Systems.

SDR Linking... The following functions are currently linked between the K3 and the SDR software: VFO A, VFO B, Mode, IF Offset, Filter Width, Preamp/Attenuator settings and TX/RX status.
The links are bidirectional, meaning that any change made on the SDR software will be reflected at the K3, and vice versa. LP-Bridge connects to the K3 using the Rig Control section of the program. The SDR App (NaP3 or PowerSDR/IF) is connected to LP-Bridge in the SDR App section.

Rig Sharing... LP-Bridge is unique in this regard, going far beyond what any other com port sharing application does. LP-Bridge actually creates a mirror K3 in memory, with constantly updated data about the current state of the hardware. Multiple programs can query the mirror about status for most, but not all commands, and receive an instant response just as though they were talking to a real K3. Commands sent other than queries, are passed on to the K3. Most of the traffic from an application is polling quer
ies, so the mirror removes the burden of responding to those from the K3. The mirror also emiminates the possibility of multiple polling commands colliding with each other trying to communicate with the K3, since they are intercepted by the mirror. The normal polling for K3 status is handled mostly by LP-Bridge. Data requiring constant updating is polled for rapidly, and lesser used functions broadcast their status from the K3 to LP-Bridge. Some commands are intenionally blocked altogether, and LP-Bridge does not allow changing the meta commands so that one app can't make changes that would be detrimental to other connected apps. For these reasons, the K3 Utility should not be used with LP-Bridge.

Hardware Output Ports... Hardware which needs frequency information, like SteppIR beams or amplifiers connect to LP-Bridge using the Output Com Port sections. In general, hardware port connections need to be connected using the Connect buttons. This process can be automated by checking the Auto Connect boxes.

Auto Launch...
Allowd you to provide paths to your SDR app and loggers so that LP-Bridge can launch all your apps when it starts. This is recommended once you have a properly configured and functional system, because it not only launches the apps, but provides proper sequencing of the port connections and app launching.


Note: The latest version of LP-Bridge should be compatible with Windows 8, and we have some users running it.

LP-Bridge is beta software. You should understand this when you use it. There may be bugs, and some things that are not finished yet, but it is solid in my testing. Report any bugs or feature requests to my email. It is also wise to monitor the LP-PAN User's Group for up to date feedback.

Before installing, make sure you are logged in as Administrator, or that your user account has admin privileges. This will save headaches, especially with Vista. Normally, if you are the main or only user, your default account will be Administrator or have these privileges. Click on one of the links below to either open and run the installation program, or save to your downloads folder, where you can open and run it. Install both the "full" version and the most recent release update the first time you install LP-Bridge. Install just the "update" version if you are just updating the program, and have already installed the full version at some point. If you ever uninstall LP-Bridge, you will have to install the "full" version again, plus the latest update.

Approved beta for
NaP3 & PowerSDR/IF  This update version is required to update version 1.09 to the  latest version. Save this file and unzip, then run the setup.exe file. It installs the executable but maintains existing settings and drivers. If it doesn't overwrite the existing v1.09 program, try running the setup.exe file as Administrator. If you have an older version than 1.09, you should do a fresh install with the file below.  This is the latest full version and should be used for fresh installs. Save this file and unzip, then run the setup.exe file. It installs the program and virtual port drivers, and registers the drivers as well.


Approved beta for
TRX-Pan 2.0.x by F6DEX (with modifications by N8LP).  Install this before installing latest Update below. 
This is the latest beta full version with all supporting files. Use this version if you do not have LP-Bridge installed on your PC. It installs the program, plus all the additional files needed to run it.  This version has been tested with K3 firmware up through v4.25 and P3 firmware 1.00.  Install this after doing above full installation to obtain latest features.
Latest beta update version. Use this to update an existing LP-Bridge installation. It will only update the executable file. This version has been tested with K3 firmware up through v4.25 and P3 firmware 1.00, and the latest versions of N1MM, HRD and TRX-Manager as of 15 February 2010.

NOTE: The instructions on this page refer to older versions in large part. Check the LP-PAN User Group for configuration information on this beta version for now.

In addition, there are postings to the LP-PAN User Group occasionally about other beta versions. You can read about the various versions by clicking on
Software Version History. The directory for the beta versions is The files have the format, where xxxx is the version number you want. Note: When updating from a very old version, you might have to re-select ports and data such as polling rate and CW Pitch, because the save file format changed at about version 0.982. If you install the full version and a newer update at the same time, this is not necessary.

Once unzipped, click on the program folder, then click on setup.exe to start installation. Accept the default installation directory. The virtual port drivers in LP-Bridge are different for each operating system. During installation, LP-Bridge Installation will detect your OS and install and register the correct versions. LP-Bridge will run on Windows 2000, XP, XP64, Vista, Vista64, Windows 7, Windows 7 64-bit and Windows 8. You will see a command console open up during installation to run the registration programs, and you will see messages that the registration was successful for the two drivers. Click OK on the two registration messages when they appear. Click Finish to finish installation. You will see a message asking you if you want to reboot. Click yes, console will close and your PC will reboot.

If asked at any time about replacing newer files on your system with older ones from the LP-Bridge installation, always keep your newer existing files. After the reboot, you can start LP-Bridge from the Start menu, or create a shortcut for your desktop. If you are running Vista, the shortcut should be set for administrator privileges (by right clicking on it and choosing the Run As selection).

Setup & Operation:

When LP-Bridge first starts, it will be in Normal mode. Below is a screen capture with the Normal mode running after it has been set up with a typical configuration. Initially, most of the boxes and selections are blank or set to defaults. The Rig Status window along the left side shows data from the rig when it is connected and communicating properly. This window is useful in checking for smooth response.

Refer to the above picture for the following section setup information...

K3 Com Port...

Com Port selector: Use this to select the com port that the K3 is connected to.

Connect/Disconnect: Click this button to connect to the K3. When it connects, the button changes to a Disconnect button. The K3 must be set for 38400 baud. The K3 must be connected before any of the virtual ports can be created.

Auto Connect: Once everything is working well, the rig connection can be automated to connect when LP-Bridge starts.

Always In Top: Check the box to force LP-Bridge to cover all other apps on your desktop.

Start Minimized:
Check the box to force LP-Bridge to start minimized to the taskbar to reduce desktop clutter.

Click Offset:
Used with TRX-Pan to cause the VFO frequency sent to the program to be offset to center digital modes midway between mark and space in the passband.

Mark Shift:
Used with TRX-Pan to allow the program to properly display the passband overlay in digital modes.

Poll Rate:
Sets the rate of polling the K3. SHould not be set less than 200ms unless you have a real serial port. Polling in the SDR app should be set approx. 100ms slower than this setting for best results.

SDR Com Port...

Com Port selector: Select an unused port number to create a virtual port for the SDR app (NaP3 or PowerSDR/IF) to connect to.

Auto Launch: Once everything is working well, launching of the SDR app can be automated when LP-Bridge starts. The SDR app path is entered in the expanded setup page, described later.

Connect/Disconnect: Click this button to create the port.

Auto Connect: Once everything is working well, the SDR connection can be automated to connect when LP-Bridge starts.
The K3 must be connected before any of the virtual ports can be created.

OutPut Com Ports...

Com Port selector: Select the port that your external hardware is connected to (SteppIR controller, amplifier, autotuner, etc.)

Baud Rate: Currently fixed at 4800 baud, not adjustable.

Connect/Disconnect: Click this button to connect to the hardware.

Auto Connect: Once everything is working well, the hardware connection can be automated to connect when LP-Bridge starts.
The K3 must be connected before the output ports can be conected.

To connect an Output port to SteppIR controller, y
ou need to connect the selected PC port to your SteppIR box Data In port. The cable to the SteppIR controller should be a DB9 female to DB9 female crossover cable. This means that pin 2 from one end should be wired to pin 3 three of the other end and vice versa. The connector on the SteppIR box uses non-standard wiring, so only wire the needed pins. Pin 2 on the SteppIR end goes to pin 3 on the computer end... pin 5 (gnd) is the same at both ends. Also, it is necessary to add a "loopback" jumper from pin 7 to pin 9 at the SteppIR end of the cable. Here is a crude diagram...


Virtual Com Ports...

Com Port selector: Select an unused port number to create a virtual port for any application (logger, CW SKimmer, PSK app, etc.) The app is set up to connect to a K3 on this port. Any baud rate is acceptable since this port adjusts automatically.

Connect/Disconnect: Click this button to create the port.

Auto Connect: Once everything is working well, the app port can be automatically created when LP-Bridge starts.The K3 must be connected before any of the virtual ports can be created.

AI1 , AI2: Forces the port to emulate Auto Information modes used by some rigs and required for some apps which don't poll for data.

Auto Launch: Once everything is working well, the app associated with the virtual port can be automatically launched when LP-Bridge starts. The program file path is entered in the expanded setup page, described later.

Pgm: Scratch pad used to enter the name of the app to help the user keep things straight

Expanded Setup Screen...

Additional setup and diagnostic tools are revealed by clicking on the Setup menu and selecting "Show" as shown below. The terminal windows along the bottom are useful for discovering comm errors with the SDR app and various apps connected to virtual ports.

PowerSDR-IF Aux CAT Port...

Com Port selector: Select an unused port number to create a virtual port to add support for a automatic preamp and split linking. This is optional, and ,ost users consider it too complicated and not worth the effort to set up. It was added to address some requests by a number of users.

Connect/Disconnect: Click this button to create the port.

Auto Connect: Once everything is working well, this Aux  SDR connection can be automated to connect when LP-Bridge starts.
The K3 must be connected before any of the virtual ports can be created.

Virtual Port Application Paths...

Use this section to provide paths to all the apps which you want to auto launch, including the SDR app.

Proper Sequencing of Operations:

Whether doing it manually or through Auto Launch / Auto Connect, the following sequencing is required...

Turn all hardware on first.
Start LP-Bridge
Connect to K3*
Create SDR port and Virtual Ports*
Connect Output Ports* (if used)
Launch SDR app*
Launch logger apps*

* These steps can be fully automated using
Auto Create / Auto Connect / Auto Launch.

Shutting down should be done in reverse order. Once the SDR app and logger apps are closed, however, you can just close LP-Bridge and all remaining steps will be done automatically.

Larry N8LP

Software Version History: Note: The name "PowerSDR-IF" below refers to the
FlexRadio Systems PowerSDRTM software modified and supported by WU2X.

Release Date
1.10 update
Bug fix for OM command on NaP3 port
1.10 full
Bug fix for OM command on NaP3 port
1.09 full
Updated Eltima drivers to latest ones.
1.08 update
Added support for NaP3 v2.15
1.07 full
Added support for Windows 8
Added changes for NaP3 v1.20
Fixed frequency reporting bug
Added support for NaP3 v1.1.0
Fixed "IF;" bug with DX Labs
Made some slight changes to the GUI, added LN command and fixed a bug.
Added support for NaP3 v1.04
Added support for NaP3 beta 3
Added support for SMH command
Added support for NaP3
Updated bargraph command support for K3 to keep in step with FW v4.39 changes
Added DDE interface for TRX-Pan mousewheel tuning and faster passband indicator response
Added a check for K3 Diversity mode
Improved polling for VFO B
Add improved Data sub-mode support for K3 / TRX-Pan.
Add support for additional TRX-Pan functions (Sub, CW pitch, dualPB, sync AM)
Add support for TRX-Pan
Add VFO updating of Output Ports when Split is invoked
Pulled due to rig control bug.
0.9981 update
Adds support for K3 Memory Editor
Bug fix for Win 7 config.ini path in installer
0.9980 update
Adds support for PowerSDR-IF v1.19.35
full & update
Fixed problem with IF command that prevented proper reporting of K3 Data Sub-Modes
Extensive changes to add all known K3 commands, and change behavior of SET command pass-throughs
Improved AI1 operation
Improved AI2 operation
Fixed bugs with AI1 and AI2
New version for PowerSDR-IF v1.19.02
Bug Fixes for PowerSDR-IQ v1.12.20 - Last version for PowerSDR-IQ
Adds support for PowerSDR-IQ v1.12.20
Enabled virtual ports 4 & 5
Added AutoLaunch path entry field for PowerSDR
Added AutoLaunch option for 2nd instance of PowerSDR

3-1-09 Autostart enabled for all real and virtual ports.
Autolaunch added for virtual port connected apps
Autolaunch added for PowerSDR
LP-Bridge "start minimized" option added
Added support for some special modes for N1MM
Fixed DXBase not working on VPorts 2 & 3
Fixed timing problems with DXBase
Fixed truncated frequencies above 99,999.999 MHz.
Fixed frequency reporting on the Output ports in Split mode.

Adds support for K3 firmware release 2.46
Adds support for HRD 4.1 Build 1989
Adds IF; and FB; outputs for the two Output Ports to support microHam band decoder

Fixed bug in Split mode for two Output Ports
Fixed bug that caused Output Port 2 to recall the com port number for Output port 1.
1. Fixed a bug where the position lines in config.ini were not being saved under certain conditions.
2. Changed the way ports are saved to eliminate the possibility of the wrong port being recalled
3. Fixed RX command problem.
Added output ports for SteppIR and other hardware.
Made a change to correct for an apparent intermittent K3 bug causing errors when polling a VPort for commands which use the K3 extended command set.
1. Changed polling in TX mode to reduce load on K3 which was causing problems with ALC algorithm in K3.
2. Added AI2 option for VPorts 2 & 3
3. Added error trapping and message for K3 port connection.
4. Fixed a couple minor bugs.
1. Fixed a problem with microHam Router and the way it and at least one other USB to serial adapter handled AI2 generated responses from the K3.
2. Re-enabled blocking of AI commands from V Ports
1. Fixed a problem with buffer overrun on microHam Router and other USB to serial adapters when polling for all the data to initially populate the virtual K3 parameters in LP-Bridge.
2. Fixed bug where polling was being unibtentionally be repeated twice each polling interval.
Initial alpha release of LP-Bridge