N6NU SDR Bridges

What's new in V3

These bridges were built first and foremost to feed WS-MAP with a full 256 kHz of bandwidth. (They also work for narrower digital modes, but the 256 kHz wideband feed is the whole point.) The bridges also deliver 3 kHz-wide SSB/USB either via VAC or TCI. V3 is a sizeable step up from the v2 series: one SDR now feeds two WS instances, there is a second receiver you can listen on, there is a sun noise meter, and the band / transverter handling was rebuilt around microwave work.

Two slices — two WS instances from one SDR

Slice 0 is the band master and the only thing that moves the SDR's LO. Slice 1 is a roamer: its own TCI server on your TCI port + 1 (40002 by default), its own dial, and it returns to the frequency it was last on. A second WS can work a different part of the same capture while the first one stays put, and slice 1 can no longer drag the LO — or the mode — out from under slice 0.

• Off by default. Turn it on with Enable 2nd slice in Settings. A single-slice setup behaves as it did in v2.
• On the Pluto RX+TX and HackRF RX+TX bridges slice 1 can transmit too. TX is first-come, first-served and non-interrupt: whoever keys first owns the transmitter until they let go.
• View → Slices opens a status window listing each slice with its frequency, mode and TCI client count, and the panadapter marks them S0 / S1.
• In every bridge except the IC-705.

A second receiver you can listen to

View → Receiver opens an independent receiver inside the capture you are already taking, with its own demodulator — USB, LSB, CW, AM, NFM — its own volume, and its own output device, so it can go to a different speaker from everything else. Tune it by absolute frequency in MHz. It costs no slice and no extra hardware: it is simply another channel inside the same IQ. Useful for listening to a beacon, or to the SSB calling frequency, while WS keeps decoding. In the SDRplay, HackRF RX+TX and Pluto RX+TX bridges. The RX bridges also gained a plain monitor audio output with a volume slider.

Sun noise meter

An analog-needle noise meter for antenna and system work: point at cold sky, press zero, point at the sun, and read the Y-factor off the gap. Selectable scale in dB per division, max- and min-hold, and an AGC checkbox that is there to be unticked — with AGC on, Y collapses toward 0 dB and the figure means nothing. On every bridge.

Microwave and transverter work

• Transverter offset per band, filled in from the SDR's IF, so the readout and the wideband window are in the band you are actually on rather than at the IF.
• New bands in the table: 9 cm (3400 / 3456), 13 cm including the Japanese 2400 segment, 2320, 5760 and 10368 MHz.
• Park modes decide where the LO sits relative to your dial: on the dial, Band center, Below band, Block, or locked to the band, each with its own per-band capture width, LO and wideband window.
• The WS-MAP / EME window center is yours, per band — it is no longer a fixed constant, which matters when the activity on your band is not where the sub-band math puts it.
• The readout shows what goes out, not where the LO happens to be parked, and the waterfall marks the 256 kHz WIDE window actually being sent.

Feeding two programs at once

A second program port sends the same wideband IQ to a second program on the same PC, with its own bandwidth — so EME65 can have 96 kHz while WS-MAP takes the full 256 kHz, from one bridge and one SDR. Linrad bandwidth is also settable per band.

Elsewhere

• Keep RX running during TX: a full-duplex toggle for stations whose receive path stays connected on transmit — it removes the gap, and the long black bar, from the WS-MAP waterfall.
• Lock replaces the old Manual override: typing a frequency always works, and Lock is what stops WS or CAT from moving you off it.
• Gain and front-end controls apply live, with no Apply click.
• TCI no longer leaves a stuck transmitter if the client disappears, and the client count covers every slice.
• Window and popout positions are remembered properly, there is a band picker on the band badge, and the whole family has new icons.
• Every V3 installer bundles the Microsoft Visual C++ runtime, which is what made the old v2.1.1 builds fail to start on a clean Windows machine.

New radios

Flex Bridge — a new bridge for FlexRadio over the SmartSDR API, taking DAX IQ for the wideband feed and the radio's own DAX audio for WS, with TX and PTT. It runs alongside SmartSDR rather than instead of it, picks the radio when several are on the LAN, and on a two-SCU radio it takes two captures from one bridge — each with its own TCI and its own band — with TX arbitrated against MultiFlex peers. It also carries an Antenna Genius row and a radio panel (power, tune, antenna, meters, PG-XL / TG-XL). It is in the list above, with its own quick-start guide.

An IC-905 bridge exists as well, but is not listed yet — it is still being tested here. If you have one and want to try it, email me.

Also in the v2 series

If you are coming from v1: every bridge speaks TCI, so WS drives it as a TCI transceiver over the LAN — frequency, mode, PTT and the demodulated RX audio on one WebSocket, with no virtual audio cabling, and TX audio too on the TX-capable bridges. The bridge and the SDR can live at the dish on a Raspberry Pi. v2 also added the IC-705 (WiFi) and HackRF One (RX+TX) bridges, the auto EME sub-band with dial snapping, manual entry with Lock MHz, headless start without the SDR plugged in, and the 96 / 128 / 192 / 256 kHz Linrad bandwidth selector with hot restart.

Raspberry Pi and Linux

The bridges build and run on the Pi and on Debian / Ubuntu / Mint. RTL-SDR .deb packages for amd64 and arm64 are served from this site; for the others, email me.

A big thank-you to everyone who has tested the bridges, sent feedback, reported a bug, or asked for a feature — a great deal of what's in V3 came straight from those notes, and it's genuinely appreciated. Please keep it coming.

— 73, Andreas, N6NU