N6NU SDR Bridges · Operator guide

QMAP Multi-Instance Guide

Run two IQ RX Bridges and two QMAPs side by side on one computer. The worked example is a FlexRadio 6600 receiving both polarizations at once, one transverter for H and one for V.

The picture

Each polarization gets its own complete receive chain: one panadapter, one bridge, one QMAP. The two chains never share a port or a settings file. They only meet at WSJT-X, which takes clicks from whichever QMAP you point it at.

Every number that differs between the two chains goes up by exactly one. That single rule is the whole trick, and it is what you repeat for a third band or receiver.
What this is, and isn't

This gives you two independent decoders, one per polarization. A station heard on both shows up in both QMAPs. It is not MAP65-style cross-polarization: each bridge sends a single channel, so nothing combines the two signals and there is no polarization-angle readout.

Port plan

Fill this in before touching any settings. The H column is simply what a single-instance install already uses, so your existing setup becomes the H chain unchanged.

SettingHVA third one
Flex
DAX IQ channelDAX IQ 1DAX IQ 2DAX IQ 3
IQ RX Bridge
Shortcut addsnothing--instance V--instance + a new name
Settings fileIQ RX Bridge.iniIQ RX Bridge - V.inicreated for you
Hardware labelFlex 6600 HFlex 6600 Vanything you can tell apart
Linrad TCP port498124981349814
Linrad UDP port500045000550006
QMAP
Shortcut addsnothing--rig-name=V--rig-name= + a new name
Settings fileqmap.iniqmap-V.inicreated for you
Port500045000550006
TCP port498124981349814
Instance ID123  (4 is the last)
NameHVshown in the title bar
WSJT-X
QMAP/MAP65 source123

Bridge settings live in %APPDATA%\n6nu\. QMAP settings live in %LOCALAPPDATA%\QMAP\, which QMAP opens for you from File › Open QMAP data directory.

Setup, step by step

Before you start
  • You need the QMAP that ships with WSJT-X Improved. The stock K1JT QMAP cannot keep separate settings for a second copy.
  • If IQ RX Bridge v2.1.1 opens a blank window and closes within a couple of seconds, install the Microsoft Visual C++ Redistributable (x64) first. Newer installers carry it themselves.

  1. Give each polarization its own IQ stream

    In SmartSDR, open one panadapter per transverter: one on the H transverter, one on V. IQ streams belong to a panadapter, so assign each panadapter its own DAX IQ channel, DAX IQ 1 for H and DAX IQ 2 for V, and set both to 192 kHz.

    Use DAX IQ, not the DAX audio channels. The audio channels are only a few kilohertz wide, which is why a QMAP fed from one shows a thin sliver instead of the band.

  2. Set up the H bridge

    Start IQ RX Bridge from its normal desktop shortcut and open Settings. These are the values that matter for this setup.

    Sound card
    Input device
    The DAX IQ 1 devicePick it from the list; the names come from Windows.
    Sample rate
    192 000 HzMatch what the Flex is sending.
    Swap I/Q
    OffTurn it on only if signals look mirrored around the center of QMAP's window.
    Input gain
    1.00×DAX IQ already arrives at a sensible level. Raising this clips; it adds no sensitivity.
    Hardware label
    Flex 6600 HShown on the bridge's status panel, so you can tell the two bridge windows apart at a glance.
    Follow WSJT-X dial
    OffThe bridge cannot tune the Flex. You enter the frequency below instead.
    Demodulate IQ → audio
    Off, if WSJT-X takes its receive audio from a Flex DAX audio channelBoth bridges would otherwise push audio to the same virtual cable. If WSJT-X listens to the bridge instead, leave this on for the H bridge only.
    Bridge settings
    Manual SDR frequency
    On
    Manual SDR freq
    The panadapter's center frequency, e.g. 432.100000 MHzQMAP labels every decode from this number, so it must match where the panadapter is actually centered.
    Transverter offset
    0 MHzOnly change this if SmartSDR shows the transverter IF rather than the on-air frequency.
    Auto EME subband
    OffIt snaps the frequency label to a band's EME center, and the Flex would not follow.
    Linrad output gain
    0 dBCheck this one. The dialog can show 20 dB on a new install and saves whatever it shows.
    Linrad bandwidth
    192 kHz
    Linrad TCP port
    49812
    Linrad UDP port
    50004
    Linrad UDP target
    127.0.0.1This computer.

    Press OK, then close and restart the bridge. The Linrad ports take effect on the next launch.

  3. Create the V bridge

    Copy the IQ RX Bridge desktop shortcut and rename the copy IQ RX Bridge V. Open its Properties and add this to the end of Target, after the closing quote mark:

     --instance V

    Start the bridge from this shortcut. The window title now ends in V, and the bridge keeps its own settings file, so nothing you change here touches the H bridge. Open Settings and enter everything as for H, except these:

    Differences from H
    Input device
    The DAX IQ 2 device
    Hardware label
    Flex 6600 V
    Demodulate IQ → audio
    OffOnly one program should feed WSJT-X its audio.
    Linrad TCP port
    49813
    Linrad UDP port
    50005

    Press OK, close the V bridge, and start it again from the V shortcut. If you prefer, the ports can go straight onto the shortcut instead; the bridge remembers them after the first launch:

     --instance V --linrad-tcp-port 49813 --linrad-udp-port 50005

  4. Check the H QMAP

    Start QMAP from its normal shortcut and open File › Settings .... Your existing QMAP becomes the H instance, so this is mostly a check.

    Input from Linrad or SDR Console
    Port
    50004
    IQ sample rate
    Auto (detect from bridge)QMAP asks the bridge on the TCP port below when it starts.
    Linrad host
    127.0.0.1
    TCP port
    49812
    Multi-Instance Identity
    Instance ID
    1
    Name
    HShown in the window title.

    Restart QMAP after changing any of these.

  5. Create the V QMAP

    Copy the QMAP shortcut, rename the copy QMAP V, and add this to the end of its Target:

     --rig-name=V

    Start QMAP from the new shortcut. It creates its own settings file, qmap-V.ini, and starts from defaults, so enter My Call and My Grid again. Then open File › Settings ...:

    Input from Linrad or SDR Console
    Port
    50005
    IQ sample rate
    Auto (detect from bridge)
    Linrad host
    127.0.0.1
    TCP port
    49813
    Multi-Instance Identity
    Instance ID
    2Two QMAPs on the same ID share click-to-work and work files, and step on each other.
    Name
    V

    Restart QMAP V so the new port and ID take effect.

  6. Point WSJT-X at the QMAP you are working

    One WSJT-X window serves both. Click-to-work needs Q65 mode and Enable VHF and submode features turned on in WSJT-X Settings.

    • In the Decode menu, turn on Accept QMAP/MAP65 click events.
    • Under Decode › QMAP/MAP65 source, choose 1 to work from the H QMAP and 2 to work from V. The switch takes effect immediately, no restart.
    • Leave Claim QMAP off. It only matters when two WSJT-X windows watch the same QMAP.
Start order

Start both bridges first, then both QMAPs, then WSJT-X. QMAP asks its bridge for the sample rate as it starts, so a QMAP started before its bridge falls back to the wrong rate.

Check it works

  • Two bridge windows are open, and the second one's title ends in V.
  • Two QMAP windows are open, titled H and V, and both waterfalls are moving.
  • Tune a strong signal onto only the V transverter. It appears in QMAP V and not in QMAP H.
  • A frequency QMAP shows matches what SmartSDR shows for the same signal.
  • With source 2 selected, a double-click on a V decode sets up the QSO in WSJT-X.

Troubleshooting

What you seeWhy, and the fix
The second bridge shows H's settings, or changing one changes the otherIt was started without --instance V. Start it from the V shortcut.
QMAP V's waterfall stays emptyIts Port does not match the V bridge's Linrad UDP port. Both must be 50005. Only one QMAP can listen on a port.
QMAP reports it cannot reach the bridge at 127.0.0.1:49813The V bridge is not running, or the TCP ports differ. Start the bridge first, then check both show 49813.
Decodes appear on the right band but at the wrong frequencyManual SDR freq does not match the panadapter's center, or Auto EME subband is on. Fix it on that chain's bridge.
Signals look mirrored around the centerTurn on Swap I/Q on that bridge.
The waterfall is yellow or redSet Input gain to 1.00× and Linrad output gain to 0 dB. Then set the colors in QMAP's waterfall window with Auto Zero, bring Zero down until the noise sits dark blue, and use Gain for contrast. The colors are display only.
A bridge warns "WSJT-X UDP listener failed"Follow WSJT-X dial is on while another program already listens on port 2237. Turn it off; the manual frequency replaces it.
Clicks in one QMAP do nothing in WSJT-XWSJT-X is watching the other source. Change Decode › QMAP/MAP65 source, and check both QMAPs do not share an Instance ID.
The bridge window flashes open and closesIQ RX Bridge v2.1.1 needs the Microsoft Visual C++ Redistributable (x64). Install it and start again.

A third instance, or a second band

Nothing about this is specific to polarization. Two bands, two receivers, or a 96 kHz reference QMAP beside a wide one all work the same way: a new instance name, every port one higher, and the next Instance ID. The last column of the port plan shows the third set. QMAP instance IDs stop at 4.

Moving the H and V pair to 144 or 1296 MHz is the same recipe again. Only the panadapter frequencies and each bridge's Manual SDR freq change.