HAM RADIO - Remote Rig Audio over IP - activating the rig's VOX PTT circuit with a SUB-TONE
with the RIG in VOX auto-transmit mode, the rig's VOX CIRCUIT on most RIG's will always cut off the very first section of any voice audio syllable or consonant when the VOX first activates, and again each time the VOX CIRCUIT is activated during the QSO....it takes a tiny bit of time for the VOX to measure the input audio power and turn on the PTT SWITCH of the RIG going into TRANSMIT MODE....
this time can be significant, since you can loose the very beginning of a word, syllable or consonant or even miss the first DIT or section of a DAH if you are operating in AFCW MODE...if you just use VOX the usual way...
However, by ADDing a LINEAR AUDIO DELAY line when using VOX to trigger the PTT to "ON" - ie for TRANSMITTING AUDIO on SSB...this experimental setup shown on the video will demo a technique to keep the first part of any voice syllable or consonant or the very first part of a CW ELEMENT from being CHOPPED OFF, or completely missed...
SETUP: picture shown here: https://imgur.com/MPECLt8
a software APP audio gate is first setup up to inject a SUB TONE(20hz) into the RIG's LINE INPUT JACK ahead of the 800 hz CW TONE....the SUB-TONE is used just to activate the PTT CIRCUIT...the volume of the 20 hertz tone is set as low as possible, but still strong enough to keep the PTT / VOX circuit working until the SUB-TONE is stopped...this takes on my K3S about -22 db of audio power at 20 hertz to get the VOX CIRCUIT to turn the PTT CIRCUIT - "ON"...then the other GATE settings are adjusted so that the GATE THRESHOLD VOLUME is above the level of the 20 hertz tone...say @18db...so...at -18db THRESHOLD SETTING, this will keep the 20 hertz tone from passing through the GATE to the rig... until the GATE on channel 1 is triggered by the actual VOICE audio or CW AFCW audio to be transmitted, from a MIC or AFCW tones....the voice or afcw tone is connected to the LEFT CHANNEL of the gate, and does not go to the transmitter...it is used only to trigger channel 2 of the gate, where the 20 hertz SUB-TONE is waiting to go through the gate to the RIG's LINE INPUT and activate the VOX CIRCUIT....once the GATE is triggered, you also adjust the gate RELEASE control to keep the gate open according to your preference..1/2 second, more or less etc...
the VOICE or CW AUDIO TONE is used to trigger the left channel of the gate to open and allow through, the RT CHANNEL SUB TONE already running on the input of gate channel 2...the SUB-TONE is low enough in pitch that it gets rejected by the RIG's transmit circuits...but the 20 hertz tone is still useful since the VOX circuit responds to it; to trigger the RIG'S VOX CIRCUIT...to activate the PTT circuit and then transmitting any audio arriving at the RIG's LINE INPUT or MIC INPUT...at the same time the VOICE or CW AUDIO TONE also goes to another SOFTWARE APP - a LINEAR AUDIO DELAY LINE plugin...which slows down the arrival to the RIG ...just enough for the PTT CIRCUIT to be fully opened and ready for transmit by the time the actual audio that will be transmitted arrives...(voice OR afcw tones)
the problem with typical VOX TRANSMITTING, is, that, it takes a tiny amount of time for the VOICE or CW audio to trigger the RIG's INTERNAL VOX CIRCUIT which will activate the PTT circuit...thus you loose the first part of any VOICE or CW ELEMENT... ADDing a LINEAR AUDIO DELAY LINE to the voice path or cw audio path to the RIG, will delay the audio just enough to allow the PTT to fully activate before the audio arrives to the RIG's line input or MIC INPUT for getting transmitted... etc...
this video also demo's using a REMOTE RIG SETUP....which depends on AUDIO OVER IP(LANorWAN)....to get the audio to & from the RIG...thus you also have to deal with packet jitter and delay..and the video will demo how much JITTER BUFFER you need to adjust for JITTER DELAY...to ensure that all packets of audio over ip arrive to the RIG ..AFTER...the PTT TRANSMIT SWITCH is all the way closed and the RIG is ready to transmit... all this depends on the quality of the home network or internet band conditions etc...
the audio you hear on this video is from a separate receiver, an R1 DC receiver...the RIG Xmitting is an ELECRAFT K3S...
FLdigi is used to send a very short DIT and DAH at 200 wpm to help discover and find the right values for the linear delay AP and SUB TONE GENERATOR...
https://launchpad.net/invada-studio/
http://plugin.org.uk/ladspa-swh/docs/...
https://calf-studio-gear.org/
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