July 2022 Blog Posts (20)

Full Duplex Fast QSK CW QSO over IP using a multipurpose Gstreamer Script on a Raspberry PI & laptop

the Gstreamer Script used in this video example:


gst-launch-1.0 -v alsasrc device=hw:4 ! "audio/x-raw, format=(string)S16LE, layout=(string)interleaved, rate=(int)48000, channels=(int)2, channel-mask=(bitmask)0x0000000000000003" ! tee name=t !…


Added by Chuck aa0hw on July 30, 2022 at 2:13pm — No Comments

clean up the audio output of your Morse Code Practice Oscillator with this DIY audio BandPass Filter

Near Zero Latency passthrough... using this Gstreamer Script to create a custom CW AUDIO bandpass filter: (CW PITCH of CPO = @700 hertz)

gst-launch-1.0 -v jackaudiosrc ! audiowsincband mode=band-pass lower-frequency=580 upper-frequency=820 length=384 window=3 low-latency=true ! jackaudiosink sync=false…


Added by Chuck aa0hw on July 29, 2022 at 11:16am — 1 Comment

Build your own FREE SDR Receiver APP for Morse Code QSO audio outputs on iCW: Mumble/Discord/Sonobus

SDR RECEIVER built from RECRI KEYER's SDR MODULES: https://github.com/recri/keyer

several common CW Transmit/RX issues show up on iCW

1. keyclicks/square wave on OP's signal

2. CW pitch/keying too soft on OP's…


Added by Chuck aa0hw on July 29, 2022 at 8:22am — No Comments

High Voltage protection/insulation/isolation between RIG/CW KEYER & a PC sound card input by Pyrex Glass & induction coils

testing using 2 ferrite bobbin core inductor coils inside thick pyrex glass measuring cups to provide high voltage isolation protection between a RIG/cw keyer and a PC soundcard's input

used for sending CW AUDIO over SonoBus by keying a TWIN-T oscillator

the output of the TWIN-T goes to a class D amp…


Added by Chuck aa0hw on July 28, 2022 at 10:30am — 1 Comment

Raspberry Pi 4 - Longwave soundcard SDR CW Transmitter - LIVE demo @ 153Khz, 216Khz & 279Khz

using the dummy sound card JACK set to 800Khz, a Raspberry PI 4 transmitter sends LongWave CW to a laptop receiver over ip using these Gstreamer scripts:


qrq@pi4b:~ $

gst-launch-1.0 -v jackaudiosrc ! "audio/x-raw, channels=1" ! audioconvert ! rtpL24pay ! udpsink…


Added by Chuck aa0hw on July 27, 2022 at 8:24am — No Comments

Key'D TLC555 Square Wave Oscillator to PURE SINE WAVE CW NOTE with Raised Cosine Edges by RECRI SDR

FLdigi is keying a TLC555's pin 4/POS rail to send out a square wave CW NOTE at 1850 hertz - goes to a PI4 usb sound card's LINE INPUT...goes to a HILBERT CELL, then a BANDPASS FILTER(centered at 1850hz) then to a GAIN MODULE(+3db) then to an LO-MIXER that allows you to choose ANY CW PITCH and still keep the bandpass audio filtering bandwidth…


Added by Chuck aa0hw on July 26, 2022 at 8:20am — 1 Comment

KXstudio's CARLA as a standalone APP to conduct QRQ CW over SONOBUS operations - using ALSA on a Pi4

- a Pi4 has a usb sound card with LINE INPUT/line output/headphone output

- fldigi is keying a 555 square wave oscillator(by connecting pin 4 of the 555 to its POS RAIL through an H11F1 OPTOisolator chip) using FLdigi's KEY BY SERIAL PORT RTS PIN feature and sends its audio output to the pi's usb sound card's line…


Added by Chuck aa0hw on July 25, 2022 at 9:09am — No Comments

QRQ CW 'copy by ear' PRACTICE using Mixxx with CW REGENERATION & a tracking CW audio bandpass filter

Mixxx is a VARIABLE SPEED audio player that works great to slow down or speed up a QRQ CW audio file. Mixxx also has a REVIEW/rewind function that allows you to repeat the last word sent as many times as you want(by hitting the keyboard letter 'A' ...you can also repeat while slowing it down... MIXXX will change the cw frequency however....…


Added by Chuck aa0hw on July 23, 2022 at 9:50am — No Comments

High Performance Raspberry Pi4 /midi keyed\ Morse Code Practice Oscillator with a tracking BP filter

this video demo's a RASPBERRY PI 4, SETUP as a high performance morse code practice oscillator using RECRI KEYER CW modules


TEENSY-LC usb midi board with recri midi-keys embed firmware…


Added by Chuck aa0hw on July 20, 2022 at 9:30am — 1 Comment

A Tracking CW pitch audio bandpass filter using 2 SDR modules from AD5DZ: BandPass Filter & LO-MIXER

RECRI KEYER sdr modules from AD5DZ:



a square wave from a TCL555 655 hertz oscillator is being keyed by FLdidi's serial port RTS PIN feature.... the 655hz SQUARE WAVE goes to the input of the sound…


Added by Chuck aa0hw on July 20, 2022 at 7:56am — No Comments

Raspberry pi 4 iCW(CW over IP) station setup - uses CARLA PLUGIN HOST(alsa) with multiple plugins

testing out CARLA's plugin host, using an alsa USB sound card directly, on a Raspberry PI 4...also testing CARLA's experimental feature, 'ADD JACK APPLICATION' to include MUMBLE and a RECRI KEYER CW AUDIO BANDPASS FILTER into the CARLA CONNECTION BAY

FLdigi is keying a 555 square wave oscillator and sending into the PI's…


Added by Chuck aa0hw on July 19, 2022 at 11:03am — No Comments

FLdigi QRQ CW keys an H11F1 FET which keys a 555 OSC 555, 555 output goes to an AUDIO to MIDI app which keys a software CPO

DEMO OF FLdigi QRQ CW sending at 80 wpm, using its SERIAL PORT RTS pin keying feature, keys an H11F1 fet opto isolator which keys a 555's (pin 4/pos) which sends its output square wave at @2600 hertz to the MIC INPUT of a laptop...which sends that 2600 555 square wave to the input of an AUDIO to MIDI app called TRIGGER MIDI MONO(TMM) TRIGGER…


Added by Chuck aa0hw on July 19, 2022 at 9:12am — No Comments

QRQ CW filter for FLdigi's CW AUDIO OUTPUT by Gstreamer Script converted to an LV2 plugin by 'Carla'

KXstudio's CARLA


CARLA allows you to add a Gstreamer script in its JACK APPLICATION feature...then once the script is loaded, you can export the Gstreamer script as an LV2 plugin on Carla's RACK where it shows…


Added by Chuck aa0hw on July 18, 2022 at 12:38pm — No Comments

GST-RTSP-SERVER on PI4, keying a TWIN-T CPO + W3NQN Gaussian BP Filter, send L16 RTP cwAUDIO over IP

- testing a PI4 RTSP RTP L16 encoded server from GSTREAMER

- testing a homebrew'D TWIN-T CPO for its QRQ CW keying ability

- testing a custom build W3NQN GAUSSIAN bandpass filter to clean up the TWIN-T CPO's edge noise and harmonics

NOTE:    QRQ CW has a better sound…


Added by Chuck aa0hw on July 13, 2022 at 8:40am — No Comments

QRQ CW net over SONOBUS - recorded from their LIVE STREAM on 7-12-2022 - using a CW REGEN method on all 3 OPs sending


ARCHIVED whole stream is located here: CRSnet.mp3 (Jul 12, 2022 11:44:49 UTC)


a CW…


Added by Chuck aa0hw on July 12, 2022 at 11:49am — No Comments

filtering the output of a TWIN-T CPO using a custom build GAUSSIAN audio bandpass filter from W3NQN

for more info on this special custom build for filtering QRQ CW, from W3NQN, please see previous videos and their notes in their video descriptions:



Added by Chuck aa0hw on July 12, 2022 at 11:37am — No Comments

using a Speaker Crossover network(woofer) to clean up a TWIN-T CPO's sidetone, reducing hf harmonics

USES a RADIO SHACK 3 way speaker crossover(woofer/BASS) that has added un-polarized electrolytic CAPs - to 'tune' it to peak signal at 700 hertz



Added by Chuck aa0hw on July 11, 2022 at 10:46am — No Comments

QRQ CW over SonoBus - cleaning up your TX sidetone using Sonobus FX input NOISE GATE & PARAMETRIC EQ

SETUP: a TWIN-T oscillator is being keyed by FLdigi's RTS SERIAL PORT feature...

the TWIN-T has noise and harmonics

use SONOBUS's native input FX DSP apps, NOISE GATE & PARAMETRIC EQ to STOP THE NOISE and CLEAN UP THE twin-t's SIDETONE before transmitting it to the other OPs listening on your…


Added by Chuck aa0hw on July 8, 2022 at 8:35am — 1 Comment

FLdigi CW serial port keying, SIDEtone audio output, change from 1500 hz to any hertz with the RECRI KEYER's SDR mixer

RECRI KEYER SDR MODULES from: https://github.com/recri/keyer

when using FLdigi's SERIAL PORT KEYING mode....the CW audio output form FLdigi changes from whatever it was set to, to a hard wired 1500 hertz... to change it back to any pitch you want, an SDR MIXER…


Added by Chuck aa0hw on July 6, 2022 at 8:14am — No Comments

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