Hardware PTT Cable Only Control (no digirig) for fldigi

1

Greetings,
A buddy loaned me his FT-2900 and I was using fldigi just holding up the radio mic to my speakers to send, and holding my pc mic to the radio speaker to receive. Worked great. We were doing BPSK1000. Zero issues. We were even using other modes to send color pics. Pretty neat.

He let me borrow his digirig with all the cables, and after setting it up and thinking about it, am I wrong in saying I don’t need a digirig for my particular application? I’m not doing any sort of rig control. Looking at the pinout for the digirig Yaesu cable, it seems like fldigi is able to use the right channel to open up the PTT. I can just use a 3.5mm stereo cable out of the back of the FT-2900 into the line in or mic on my PC like I have been. Then I can get a cable from the stereo out on my PC soundcard (no digirig) and trace the left channel to the mic input on the RJ12 connector, the right channel to the PTT on the RJ12 and ground to ground. Obviously, I’d have to be careful about accidentally sending whatever is going through, or might come through my PC speakers since anything on the right channel would trip the PTT and activate the radio. I could put in a foot switch or something to have physical control over it.

Am I missing something in my understanding of how fldigi/digirig is working in a hardware controlled PPT application like this?

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i won’t go too deep, you’ve observed a send/receive without any ‘extra hardware’ so i’ll try to explain why people might choose an interface with or without rig control.

so your rig is obviously an FM radio.
FM absolutely can rx/tx soundcard mode data. you’ve done it.

the ‘thing’ is, the soundcard modes will use the same bandwidth as ‘talking’ so you cant have multiple conversations on the same frequency and there is no ‘weak signal’ advantage.

no big deal, just the difference between SSB and FM.

now, onto interfaces.
having a direct soundcard to radio connection eliminates unwanted audio from being transmitted as well as increasing the signal to noise ratio which leads to better tx/rx.

now, if you’re ‘full quieting’ with your qso partner, then there is less of an issue with s/n ratio. but that’s FM
:slight_smile:

the ptt side of things is as varied as you could imagine.

there are vox type ptt that use one channel of audio to trigger, as you stated.
there are comport rts/dtr toggle options as well as gpio (a soundcard pin togggle)

the second/third options are my favorite. they are on/off and do not rely on audio volume settings to trigger.
a PTT controlled by the software you’re using to encode/decode soundcard digi modes will result in quick turn around and positive key/unkey states and would be absolutely crucial in the ‘jt’ modes.

digirig lite, has the gpio style as well as the vox style.
digirig lite also does not include rig control serial port.

the ‘ptt on left or right channel’ is NOT a on/off ptt key.
what happens is a steady MONOTONE is output on the left or right in order to trigger a VOX keying circuit. it doesn’t pull the ptt pin of a mic connector to ground in order to tx.

do NOT send left or right audio to the ptt pin of the mic
you need a keying circuit/interface or the radio must be vox capable on its own.
(still no connection of left/right audio to the ptt pin)

so we’re on to rig control.
as you stated, your rig wouldn’t benefit from rig control that is present in the digirig mobile (but wouldn’t hurt anything of course).

i hope that helps some
:slight_smile:
good luck
kb0wlf

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