Raspberry PI remote VLF RF over IP Rcvr::RE-Transmitter - Local PC SDR VLF Receiver - QRQ CW example

experimental setup to QSO QRQ CW at 18Khz VLF RF over ip - using a PEER to PEER Gstreamer PIPELINE TCP/ip setup and a Raspberry PI as a REMOTE VLF RX/ RE-TRANSMITTER

a PI2B is setup to RECEIVE another OP's VLF RF over IP transmission(CW at 18Khz) using a Gstreamer rtp TCP/ip PIPELINE - using the WAVPACK CODEC...the PI2b decodes the WAVPACK 18Khz CW and sends it out its own audio jack to a 30 watt audio amp...the output of the audio amp goes to a 9/1 Balun, the output of the 9/1 balun goes to a small 40 foot wire loop antenna in the same building as the PC soundcard SDR RECEIVER

the PC soundcard SDR RECEIVER is using a FERRITE CORE LOOPSTICK antenna to pick up the pi's 18Khz CW transmission... the laptop's RECRI KEYER SDR modules take it from there, filtering, decoding, and sending it to the speaker/heaphones

the REMOTE OP is sending CW on their PC to the PI, using the RECRI KEYER CW modules, in this case, for QRQ CW, the RECRI KEYER CW KEYBOARD...it can send directly at 18Khz...and the output of the CW keyboard branches...one branch goes to the OP's own soundcard(mixed down to 700hz) for monitoring the sidetone...the other branch sends 18Khz to the input of a TCP over PI wavpack encoding gstreamer pipeline that is sent out over the internet to the PI's external IP ADDRESS

here is op's PC Transmit to PI Gstreamer VLF RF over IP Pipeline Script: ***********************************************************************************

gst-launch-1.0 -v jackaudiosrc ! audioconvert ! wavpackenc ! wavpackparse ! rtpgstpay ! rtpstreampay ! tcpclientsink host=(EXTERNAL IP ADDRESS OF THE REMOTE PI RCVR/re-transmitter) port=7373 sync=false async=false

here is the PI's RX/TX Gstreamer VLF RF Over IP PIPELINE SCRIPT: *********************************************************************

pi@raspberrypi ~ $

gst-launch-1.0 -v tcpserversrc host=192.168.1.130 port=7373 do-timestamp=true ! "application/x-rtp-stream, media=(string)application, clock-rate=(int)90000, encoding-name=(string)X-GST, caps=(string)\"YXVkaW8veC13YXZwYWNrLCBjaGFubmVscz0oaW50KTIsIHJhdGU9KGludCk0ODAwMCwgZGVwdGg9KGludCkzMiwgZnJhbWVkPShib29sZWFuKXRydWU\=\", capsversion=(string)0, payload=(int)96" ! rtpstreamdepay ! rtpjitterbuffer ! rtpgstdepay ! wavpackparse ! wavpackdec ! audioconvert ! alsasink sync=false async=false

NOTE: two RTP Gstreamer elements are being used, rtpgstpay & rtpstreampay ... the rtpgstpay has a caps=(string) line of code in it, you will have to copy from the PC TRANSMITTER script to place it on the PI RECEIVER script - using double quotes that have to be placed in the PI's script...look at the PI SCRIPT above and note the 2 double backslashes, one before and after (string)\"YXV****** AND ***WU\=\"

on the TRANSMITTER script, Gstreamer will not include those BACKSLASHes , you will have to add them to the PI's script... the first back slash goes BEFORE the quotation marK, the 2nd back slash goes just before the last quotation mark....

this PI RX/RE-TX Gstreamer script, when just using ALSA and nothing else running on the PI, runs pretty low on the PI CPU usage .... (the PI in this demo is a pi2b) the PI RX gstreamer script includes a RTP JITTER BUFFER and can be adjusted up or down according to the internet band conditions

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Comment by Chuck aa0hw on February 4, 2021 at 11:01am

Here is a 2nd video showing pictures of the HARDWARE used for QRQ CW VLF RF OPERATIONS

This video shows a Raspberry pi2b being setup to act as an... - 18Khz CW VLF RF over IP receiver - RE-transmitter -

Gstreamer scripts are used to provide the VLF RF over IP from the REMOTE OP to this REMOTE PI which is using a Behringer UCA222 USB Soundcard (ALSA audio)

NOTE: this video is a follow up from the first one here: https://youtu.be/SnB6huopgDw (and using the same basic setup for both the hardware and software)

in this video some pictures of the VLF operations hardware are included for the VLF PI transmitter & VLF sound card receiver

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