Pulse Density Modulated HF CW Transmitter/afcw mode\ {Saves Battery Power !} for portable operations

[Chuck aa0hw]

since the TRANSMITTER is not using full duration CW ELEMENTs(using AFCW MODE)(a2) Battery Drain should be less when operating portable via PDM-CW methods

ZAMGATE is the PDM-CW encoder: https://www.zamaudio.com/?p=976

GSTREAMER SCRIPT provides the PDM-CW pulse train:

gst-launch-1.0 -v audiotestsrc wave=ticks tick-interval=10000000 sine-periods-per-tick=1 freq=2000 volume=.9 ! audio/x-raw, channels=1 ! audioconvert ! audio/x-raw, channels=1 ! audioconvert ! queue ! jackaudiosink

TRIGGER-MIDI-MONO is the PDM-CW DE-coder: https://lsp-plug.in/?page=manuals&section=trigger_midi_mono

RECRI KEYER provides the SDR MODULES to FILTER the TRANSMIT PDM-CW pulses before going to the RIG, and provide the midi input CW keyer for TriggerMidiMono AUDIO input TO midi OUTPUT APP https://github.com/recri/keyer

[Chuck aa0hw]

Here is another example of Pulse Density Modulation CW MODE, for a HIGH Q  LARGE FERRITE ROD VLF TRANSMiT ANTENNA:

FERRiTE ANTENNA = TEN 7 inch Ferrite rods stacked together to fill the inside of a 2 inch diam. AiRDUX AiR WOUND COiL https://airdux.com/

coil is parallel resonated by a 1.1uF CAP/coil taps, for max signal output on the VLF band at 8Khz

NOTE: using this T/R device, this setup can be modified easily to perform full QRQ QSK operations https://www.qrpkits.com/eztrswitch.html

FOR PORTABLE OPERATIONs: using PDM-CW MODE, saves battery power, since for each CW ELEMENT, the RF AMP is only operating 1 tenth of the time compared to full duration CW ELEMENTs

PULSE DENSITY TICK STREAM by Gstreamer script: gst-launch-1.0 -v audiotestsrc wave=ticks tick-interval=10000000 sine-periods-per-tick=8 freq=8075 volume=.99 ! audio/x-raw, channels=1, rate=48000 ! audioconvert ! jackkaudiosink

SOUND CARD SDR MODULES used in this demo are from RECRI KEYER:

https://github.com/recri/keyer

[Chuck aa0hw]

another example of saving a lot of drain on the portable battery packs, by using PULSE DENSITY MODULATED CW, this time a THROUGH THE EARTH, CAVE RADIO COMMs example is DEMO'd

to save drain on the battery packs, when PDM-CW is being used for THROUGH THE EARTH, CAVE RADIO comms between CAVE and SURFACE, by using PDM-CW techniques, the VLF TRANSMITTER POWER AMP is only ON for a fraction of the time for each CW ELEMENT being transmitted, compared to FULL DURATION CW ELEMENTs where the VLF TRANSMITTER POWER AMP is on for the WHOLE LENGTH of the CW ELEMENT

this demo is using TRIGGER MIDI MONO instead of ZAMGATE, for the PDM-CW DECODER on the RECEIVER the use of the HIGH Q very narrow bandwidth CW VLF FILTER is crucial for getting the PDM-CW DECODER to work effectively

when the 1ms pulse hits the FILTER the FILTER RINGs due to its high Q setting, it elongates the 1ms pulse by a substantial amount...to the point where the CW ELEMENTS(shown in RED on the SCOPE) after going through the filter, look virtually complete

GSTREAMER PULSE TRAIN used by the ZAMGATE PDM-CW TRANSMIT encoder:

gst-launch-1.0 -v audiotestsrc wave=ticks tick-interval=40000000 sine-periods-per-tick=3 freq=3000 volume=.5 ! audio/x-raw, channels=1, rate=48000 ! audioconvert ! autoaudiosink

for more examples of PDM-CW see this playlist:

https://www.youtube.com/playlist?list=PLfFan4sDonOfd-46mK93s1v5em5B...

for more examples of THROUGH THE EARTH, diy CAVE RADIO COMMs see this playlist: https://www.youtube.com/playlist?list=PLfFan4sDonOdYNelBw7UtQPfEBcr...