FRStack - Flex Radio SmartSDR Companion Utility

FRStack version 3 was designed to be used with SmartSDR / Flex 6K version 2.5 or later and 3.0.24 or later, Flex PGXL, SPE 1.3, 1.5 and 2 Amplifiers and SteppIR Antennas. Many of the features in FRStack come from FRS Community, Radio Owners and Staff input. Thank you for making FRStack better.

FRStack displays a list of Active Slices, Most Recently Used (MRU) Frequencies, a list of Memories, a list of Favorite Memories, a list of Scan Banks, Mode Memories, the Transmit Profiles, Mic Profiles, Global Profiles and the Radio Memory List.

FRStack can display Spots on the radio's panadapter by monitoring up to 4 Telenet Spot Clusters.

SmartSDR V3 supports multiple clients, you must bind FRStack to specific client in order to target the client you wish to Tune, MOX or set TX Band Settings. You can specify which client to bind to from command line with /client=_StationName_. You can also view all client's slices by using the Radio, View / Sync Client Slices menu. If you want to only use the View / Sync Client Slices feature launch FRStack with the /clients command line argument. If you want to bind to multiple clients at the same time launch another copy of FRStack.

Select a Slice window to designate the target slice for commands. The context menus are accessed by right clicking UI objects.

FRStack monitors the radio's slice frequency, when the frequency is in use for 15+ seconds it is recorded as a MRU band entry. If the frequency shifts less than 1K in either direction the current MRU is updated. When the MRU list reaches its limit the oldest MRU entry is removed. When a MRU button is selected the active Slice is set to the buttons information.

Memory buttons can be created from the context menu of a Slice, MRU tab background, MRU Band label and MRU button. A Memory can be linked to one of your TX Profiles and or MIC Profiles, this is optional. When a Memory button is selected the active Slice is set to the buttons information and the TX Profile / MIC Profile is also selected. When a Memory Band count reaches its limit a warning is displayed, you must delete a current memory to add new one. You can also increase the memory limit in the options.

The Scan Bank feature allows you to create up to 10 frequency lists called Banks. Scan Bank frequencies are created in a similar fashion as Memories using the context menus of MRU or Memory frequencies. A Scan Bank scan operation is started by using the Slice's context menu to select the Scan Bank of your choosing. The Scanning menu item lets you set the Scan Dwell time, Mode and Scan Mute settings.

Mode memories are just like regular memories except they do not set the Frequency. This way you can create your favorite SSB, CW or Digtial mode settings then apply them to any frequency.

SSB Meter Level Mute feature will mute the active slice when the current meter level is below a user selected level setting. This is a poor man’s squelch for SSB.

PGXL amplifiers can be set to Operate or Standby mode.

SPE amplifiers can be controlled from a SPE tab or the Amplifier menu item.

Tune detection will optionally set your PGXL or SPE amplifier to Standby to allow your Frequency detecting auto tuners (like the HF-AUTO) the opportunity to tune at a low power setting. Once tuning is complete the AMP is optionally set to Operate. Tune menu item in FRStack does not require any additional TX Delay however detection of Tune initiated from SmartSDR/W, SmartSDR/M requires up to a 150ms TX delay to prevent amplified tune RF from being emitted.

Full Duplex protection provides an automatic method to disable FDX when your 2 receiver radio slices change antennas. Usage scenario is two slices on different bands using different antennas. The radio's band pass filters protect the receivers from RF on other bands. When either slice is changed to the same band or remove filters (WIDE mode) you now are transmitting with no band pass protection on second receiver. This feature turns off FDX when these conditions exist to prevent RF from entering active receiver. You can control which antenna inputs are protected.

UDP Radio information feature will send data to 1 - 4 configured IP + Port combinations. Use this feature to drive accessory / companion applications like HF-AUTO Antenna Tuning software.

  • Slice S-Meter feature
  • Swap Slice settings with another slice
  • Mute all other Slices other
  • Tracks most recently used (MRU) Slice settings for easy recall and storage to memory
  • Save Slice and MRU settings to a Band Memory or Radio Memory
  • Apply labels to memory buttons
  • Favorites tab and ability to mark Memory as a Favorite
  • TX Profile tab and ability to link Memory to a TX Profile
  • MIC Profile tab and ability to link Memory to a MIC Profile
  • Global Profile tab with Program Launch feature
  • Radio Memory tab allows you to Apply or Delete Memory from list
  • Options to change button Font Size and Color and default behavior
  • Remember window position and state
  • Mini Memory Window option to view all Band Memories in less screen real estate
  • CWX Window allows access to CWX Radio features
  • Hotkeys for common radio and slice functions MOX, TUNE, ATU, VOX MUTE (Lineout mute) VOLUP, VOLDOWN (Lineout volume) SMUTE (Slice mute) NB, NR, ANF (Slice DSP) and many more
  • Band Edge Beep Feature - band edges are configured in the BandEdges.cfg file. Currently the file contains US settings.
  • Band Label Feature - band mode and license requirements are configured in the BandLabels.cfg file. Currently the file contains US settings.
  • MOX control from COM Port - Use a hand or foot switch on a Remote PC
  • Sync Client Slices feature will keep clients' slices in sync with each other. The purpose is to allow the use of Maestro as a control surface for SmartSDR when co-located. You must not bind to a client for this feature to work.

Version History


Version   Download
Enhance Radio Filter Sharpness API
Add radio memory double click action
UDP Network Info - Adds RadioMox and ActiveRadioMox
MOX state added to UDP Network and Web Socket information

Add Radio Filter Sharpness API
Updated StreamDeck RestCall Action which makes it easier to switch URL Domain for all buttons

Bug fixes
Auto Shrink User Interface feature

Rest API bugfix

Rest FRStack/MODESETSDAX API - DAX enabled / disable by TX Slice's Mode

Options MOX tab now DAX / MOX tab - New feature: DAX enabled by TX Slice's Mode
Custom Functions Add-in DLL Feature - allows you to extend Menu, Hotkey and Rest API

SteppIR control adds AUTOTRACK, Retry logic, Multi-client bugfix S-Meter data returned in UDP Meter data and Web Socket formats
Add Rest API Radio: TXIHIBIT
Update Rest API Slice: INFO adds INDEX property
Meter level Mute (Squelch) tooltip is dbm level
UDP Data add app node name set to FRStack


Add S-Meter data to UDP broadcast
Add Rest Slice DAX setting

Allow Rest API to be called from other clients feature fix

Add Radio Rest API for PROC and PROCLEVEL
Add Radio Hotkey for PROCUP, PROCDOWN
Fix non-US numeric formatting
Spot bugfixes

Memory Button Tooltip timeout feature
Update Spot Source feature - Add Send command & Keep alive logic

Update Spot Source feature - Expose Init command, add optional SSID
CWX Window - Add Escape key to clear CWX buffer

Add Spot Source feature, configure in View, Options, Spot tab

Add Radio Meter information UDP Broadcast feature
Add SteppIR TX Inhibit both ANT option

Add CW REST API and Hotkeys
Add SPE Amplifier V1 support
Improve SteppIR receive logic
Improve logging for diagnostics sessions

Add SPE Open AMP on Connect feature
Add Slice Save as Favorite Memory
Add Favorite Tab Context Menu; Sort by Label, Group by Mode
Add Radio Rest API for Monitor settings
Rest API bug fixes for Slice command

Add SPE Turn On/Off DTR feature
Add Hotkey and SPEAMP Rest API CLOSE command
Add Menu, Slice Rest API and HotKey to Center Panadapter
Bugfix Slice Rest XIT / RIT API

Add Slice Rest API to target specific slice A-H
Add Slice Rest API SPLIT and CLOSE commands
Update FDX Protect feature
Stream Deck profile updated with Slice specific buttons

Add SteppIR REST Radio API
Add FDX Protect feature
Add UDP Radio Info messages feature
Stream Deck profile updated with SteppIR & Panadaptor Width buttons

Add TX Filter Low / High to REST Radio API
Add Swap Slice to REST ActiveSlice API

Add ATU command to REST Radio API
Add Frequency Entry command to REST Radio API
Add Profile selection to REST Radio API

Add REST API for SPE Amps
Stream Deck Rest Plugin - add multiline Prefix and Suffix

Add Hotkeys Filter, MIC, Power levels
Add REST API for StreamDeck and other integrations

Fix deadlock when changing Global Profiles

Add Hotkeys for Slice Mode
Hotkey Editor File Load / Save feature

Improve View / Sync A & B Client Slices feature
Support for SmartSDR V2.5 and 3.1.0
Support FlexAPI V3.0.24

Improve View / Sync All Client Slices feature
Bug fixes

multiView support
TX Band Settings view / edit
Sync Client Slices feature will keep clients' slices in sync with each other. The purpose is to allow the use of Maestro as a control surface for SmartSDR when co-located. You must not bind to a client for this feature to work.


Release   Download
Version warning for V2.5+ fix

Version warning for V2.5+

Add hotkey for RX & TX EQ Enable

Swap Slice A with D bugfix
FRStack Spot menu removed by other Spot apps fix

Slice Menu - Frequency Edit
Reduce size of Slice S-Meter
Spot Menu Enable now enables required Hotkeys menu bugfix

Mouse wheel on Slice changes frequency by step
Mouse wheel click increases step
Slice new menu items for Mode, BW and Step
MRU memory stack - sort by Freq or Time
New hotkey and spot menu for Add Memory
Add 2200 and 630 bands
Help window adds Ctrl + / - Zoom
Add to radio memory feature bugfix

FRStack menus via Spots for SSDR 2.3.7
New menus and hotkeys for Panadapter Band and Segment Zoom
Add Hotkeys for Active Slice Lock, Radio FDX
New SPE Amp window, SPE hotkeys and larger bold Power, V, A and SWR font
Fix Scan Memory Skip function
Update to how windows positions are restored

Add +RX menu with RXADD & RXDEL Hotkey
Add SPLIT menu item on Slice with SPLIT Hotkey

Fix SmartLink Auth0 issue

Live mode for CWX Window
Program Launch now has optional RUN menu on Main Menu
Add USB Relay control feature added; accessed from Program Launch context menu

New SPE Amplifier Tab and Menu Items
Memory option to set Panadapter Bandwidth

Active Slice Frequency Up / Down hotkeys
Radio / Maestro Tune disables RCA TX (external AMP)
Meter window hides PGXL meters when AMP not detected
Fix initial tab selection

FM Reverse menu item and active slice hotkey
Slice specific MUTE Toggle Hotkeys
Installer creates Firewall rule for both Public and Private Profiles

Tune in FRStack RCA TX Disable feature
Memory Add DAX option of 'Not Set'

Flex-6400 / 6600 support
SmartLink Support
Adds Mode Memory Tab
Adds CWX Window + Hotkeys
AGC Mode + Threshold
Diversity Menu + Hotkeys
RF Gain Menu + Hotkeys
RX TX ANT Menus + Hotkeys
PGXL Menu + Hotkey, Meters
Tune in FRStack sets PGXL to Standby
--serial=[radio sn] Command line support


Version   Download
Swap Slice fix: Mute & TX states stay with each slice by default

Swap A & B-H Slices Hot keys
Bug fix for loading RX EQ settings

Slice Panadapter Bandwidth Menu Items & Hot keys
Bug fix for Profile load slice cycling (relay clicking)

Slice S-Meter peak hold indicator
Meter window context menu additions:
   Meter bar show / hide
   Display meters horizontally
   Select which meters to display

Meter window add graphical bar
Meter window Power & SWR uses 20 sample peak hold
Memory now records radio RX EQ, optional apply

Bugfix for Meter scaling
Add Hotkeys for SCAN BANK ADD, STEP size
Add keyboard delete on MRU, Memory and Scan Tabs
SmartSDR / Flex SDK V1.11 Support

Slice S-Meter feature
Meter Window Temp in Fahrenheit option
Squelch now works for all Modes
Support meter scale changes for V & A

Version   Download
Bugfix - Change slice command order
1st time CW Color changed to Orange
Add Reboot Radio menu item - Restarts radio
Add Mode Color feature, Options dialog allows you to adjust button color based upon mode
SmartSDR / Flex SDK V1.9 Support

Version   Download
Add Scan Memory quick capture feature - Double click on Slice
Add Disconnect GUI Client - Radio Menu item + HotKey (GUIOFF)
Enhance Global Profile Program Launch Editor
SmartSDR / Flex SDK V1.8 Support

Version   Download
Bugfix - Windows 7 Edit Memory crash

Increase Scan Banks count to 20
Bugfix Program Launch Show Normal option

Program Launch upon Global Profile Selection
Mute All Slices Menu Item And Hotkey

Bugfix - SSB / AM Squelch function failed when there was no Slice A

Stack Memory - add support for APF Enable / Level Settings
Meter Window - Context menu Transparent option

SmartSDR / Flex SDK V1.6 Support
Adds Slice WNB Control
Adds MIC Profile Tab
Add Meter Window - Voltage, PA Temp, TX Power Out / Reflected and SWR
Squelch (Meter Level Mute) - Slice Mute enable option
Squelch (Meter Level Mute) - DAX assignment follows Mute option; A=1,B=2,etc.
Squelch (Meter Level Mute) & Scanning now work together
Main window Tab selection Option
Mini Window selectable Always-On-Top feature
Remote MOX Switch now supports CTS & DSR with Pin level; Added debounce logic
Scan Tab - Band Label now a Start Scan button
Scan Tab - Memory button click stops scanning then sets scan slice to memory
Scan Tab - added Skip Memory option

Version   Download
Fix DIGL/U Offsets

Memory editor
Support for new Demod modes
Meter Level Mute now works with SSB, AM and FDV
Meter Level Mute now for each Slice
SmartSDR / Flex SDK V1.5 Support
Support for RTTY and DIGL/U Offsets

Version   Download
Numeric conversion culture bugfix
Band Label Feature - Shows mode and license using color and letters
Band Edge Beep Feature
Scan Bank Feature - Create and scan up to 10 groups of frequencies
SSB Meter Level Mute - Poor man's Squelch for SSB
MOX control from COM Port's DSR - Use hand or foot switch on Remote PC
SmartSDR / Flex SDK 1.4 Support

New global hotkeys - APF, APFUP, APFDOWN

Enhanced Radio menu items
Enhanced global hotkey list
Supports FlexRadio SmartSDR / FlexLib 1.4.11

Add global hotkeys to toggle VOX and SMUTE (slice mute).
Radio menu has new Slice features
  On slice set enable TX (renamed)"
  On slice set mutes other slices (renamed)
  Active radio slice enable TX (NEW)
  Active radio slice _Mutes inactive slices (renamed)
Bug fixes

Supports FlexRadio SmartSDR / FlexLib 1.4.3
Create global hotkeys to invoke MOX, TUNE, ATU, MUTE, Volume, NB, NR, ANF.

Radio menu has new Slice features
  Enable Hotkeys
  Hotkey Editor
  Enable TX on slice set
  Slice set always enables TX
  Follow radio active slice
  Slice set mutes other slices
  Radio slice active mutes inactive slices
New Slice panel background context menu
  Lineout Mute
  Headphone Mute
  Binaural RX
  Monitor TX
New Memory button context menu items
  TX Enabled
  Mute Enabled

Supports FlexRadio SmartSDR / FlexLib 1.4
Radio Memory List - Create, Apply and Delete Radio Memories
Memory Mini Window - reduced screen footprint

V is fifth public Beta release of utility.
Favorites Tab and ability to mark Memory as a Favorite
TX Profile Tab and ability to link Memory to a TX Profile
Option to change button Font Size and Color
Import File now merges with existing memories
Replace horizontal button scrolling with wrapping

V is fourth public Beta release of utility.
Fix MRU button promotion issue
Fix Slice info / tooltip refresh issue

V is third public Beta release of utility.
Remember window position and state
Add slice and button tooltips
Support for bands above 100 MHz
Update bands labels

V is second public Beta release of utility.
Support for frequency outside US Bands

V is the first public Beta release of the utility.
Swap Slice settings with another slice.
Tracks most recently used (MRU) Slice settings for easy recall and storage to memory.
Save Slice settings to a Band Memory.

Looking for portable versions of FRStack Web APIs

This version of FRStack provides REST APIs for RADIO, SLICE, UDP, PGXL AMP, SPE AMP, SteppIR Control
See how Node-Red users are leveraging FRStackWebApis by visiting nodered-hamradio on

Click to view README

Raspberry PI Version

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