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If I might add a few comments to this post.
It does beg for a better understanding from a rookie question.

What do you need to connect the sound card and the radio?
TX wire
PTT wire
GND
RX wire but the radios often have TWO separate pins for receive audio: 1200 baud and 9600 baud.
Squelch option (that’s pin 6 on the MINI DIN) - I don’t use this one.

The first amateur radio non-voice "data" mode (other than CW and RTTY) was AX.25 packet radio. It originated in the late 1970s/early 1980s. This was decades before personal computers with sound cards became ubiquitous, especially in ham shacks, Data? send/receive was done from a Teletype machine or "dumb terminal" connected to a radio via a hardware device known as a TNC ("terminal node controller").
??? The TNC was basically an advanced modem designed for two-way radios. It was loosely based on the Bell 202-standard? 1200-baud landline modem, and often used the same then-current modem chip as the land-line counterpart.? TAPR (the Tucson Amateur Packet Radio Assn) developed a standard reference design known as the "TNC-2" that was based on a Z-80 8-bit CPU and originally 128K of RAM in the early 1980s. Thousands of TNC2 clones and variants were made by at least half a dozen companies including PacCom, Heathkit, AEA, MFJ and others in the 1980s and 90s.?

The land-line version of a '202 modem could send and receive at the same time. The radio version had to deal with the fact that normal two-way radio is one-way-at-a-time. Part of the added complexity of the TNC was circuitry that could monitor the radio receiver's hardware squelch line. This prevented the TNC from transmitting while someone else was using the radio channel. This is the? origin of the "squelch/COR ("carrier-operated-relay)" on the DIN port.??

In the beginning, packet TNCs were connected to the radio's mic and speaker jacks since the 1200 baud Bell 202 standard had been designed to work over voice-grade phone lines (300-3000 Hz response) using Audio Frequency Shift Keying between 1200 and 2200 Hz tones.?

In the push for higher data rates, the 9600-baud G3RUH modem introduced direct FSK of the radio's carrier (rather than audio tones). It requires direct DC connection to the radio's FM discriminator on receive and direct DC connection to the radio's modulator.on transmit.?
??? While it was successful with technically-knowledgeable packet network builders, it never gained wide acceptance with casual appliance-operating end-users because it required (horrors!) cutting into the radio's interior to connect.?? Further, "9600" is much more intolerant of incorrectly-set modulation levels,? noise, weak signals, multi-path propagation, etc.?? Today, it is used mainly for "trunk" links between major digipeater sites, BBS systems, etc, while end-users continue (4 decades later!) to use the much-more hassle-free 1200 baud AFSK mode. ?

When the miniDIN-6 "data" port started appearing on radios in the early 1990s, it was a way to make connecting to the RX discriminator and TX modulator easier , eliminating the need to hack the radio for 9600 mode.? You could now plug a TNC in G3RUH 9600 baud mode directly into the rear panel of the radio.
??? These days, with the hardware TNC function long since replaced by "smoke, mirrors and software" inside the PC using a soundcard, the same DIN port now serves as the connection point for "sound card interfaces.

?

so the sound card ought to have at least FIVE wires to connect to the radio . Right?

Not really...?? Until VARA burst upon the amateur radio scene a couple of years ago and started pushing the limits of data transmission over FM radio, there was virtually no call for the wide-band direct-discriminator "9600" connection by end users .? All the other digi modes that have proliferated over the last 30 years or so (SSTV, PSK31, JT-65, FT-8, MFSK, MT-2000, Olivia, Contestia, etc work just fine through the "1200 baud" speaker-like connection.?

Especially on HF, where all data modes are used on some variant of SSB. (The discriminator "9600" connection is uniquely an FM thing. It doesn't exist on AM / SSB / CW modes of a receiver.)

The SignaLink has the RJ45 (8 pins) socket to a radio. Lots of options, and lots of S-Link to radio cables to choose from.
No problem hooking up a SignaLink to all six wires of a MINI DIN port.
The DRA with the 6 pin MINI DIN socket has all six wires - direct to the radio’s 6 pin MINI DIN.
The DRA -SR RJ45 has the same radio connector as the SignaLink - no problem.
Other DRA sound cards have a switch or jumper to select EITHER 1200 or 9600 baud for RECEIVE audio.


Here is the issue - the DigiRig has a FOUR-pin plug/socket (TRRS) to connect the sound card to the radios with 6 pin MINI DIN.
But we know we want FIVE wires for the option of TWO receive paths, 1 transmit path, 1 PTT and a ground.

1)? There is no such thing as a 3.5mm 5-contact "TRRRS" connector. The designer would be forced to use a larger connector, such as a mini-DIN or round 8-pin MIC-type jack.

2)? Again, until VARA burst upon the world, there was really no call for the discriminator connection by end-users.?

?

It would have been possible to design the DigiRig to also have some kind of jumper or switch to select the RX audio but alas, it’s input from the RADIO is a simple FOUR pin TRRS socket and plug.
So the DigiRig can only have FOUR wires, not FIVE, due to the limitations of a TRRS socket.
Thus, the RECEIVE audio path is now determined by the physical wiring of the CABLE itself.

It’s annoying if you want to change back/forth from 1200 to 9600 but that’s life with only four wires.

So which would you prefer, especially in the field??? Swap an external cable or have to open up the box and shift (or solder) nasty little jumpers?

On FM rigs that I’ve used (Icom 2720, 2820, 746Pro) that have that 6 pin MINI DIN port I am fairly sure that the RECEIVE audio is always available on both pin 4 (9600 baud) and on pin 5 (1200 baud) without any MENU item to select.
The same is true on a Knwd D700 and Knwd V71A - all use the same 6 pin MINI DIN port.
It is the TRANSMIT audio that comes into the radio from the sound card on pin 1 that gets routed inside the radio for a 1200 baud path (pre-enhanced, filtered) or via a 9600 baud path (more direct to modulator).

On virtually all FM radios, the RX discriminator output (a.k.a. "9600 baud") is always live regardless of any menu selections.? On multi-mode radios, again, it will only function in FM-based modes; no signal will be present here? on AM-CW-SSB modes.

Normally, it's only the function of the single radio? INPUT pin (TX) that gets shifted by menus.

I have a modified SignaLink with a small toggle switch on the chassis that allows me to select EITHER pin 4 or 5 for RX audio.
So on the fly, I can switch between pin 4 direct or pin 5 (de-emphasized and filtered RX audio).

This is EXACTLY what I do with all my home-brew interfaces.? Here are a couple:
:

The small one is intended to be Velcroed to the back of an iPad mini. The 4-conductor TRRS plug goes directly into the combined headphone-mic-headset jack of the iPad.? Both interfaces have 6-pin mini-DIN jacks - you use a standard min-DIN6-to-miniDIN-6 cable to connect to the radio.

These interfaces are completely self-powered by the tones generated by the sound card app on transmit. No serial port, no USB, no batteries and no 12 VDC power required!? Just record and play audio connections to/from the computer, phone or tablet.

I did this only for testing purposes - looking at audio coming from a FM analog repeater, when used for VARA FM.

I bought a couple of “break-out” terminals that I intend to connect to my DigiRig Mobile V1.9 and Mini DIN 6 port; thus, I can change from RX on pin 4 to pin 5 without changing the actual cable.

I have made up a?? miniDIN-6 male? - to - miniDIN-6 female cable about a foot long with a? "goiter" in the middle with a SPDT mini toggle switch for this purpose.? To route either RX audio or discriminator audio from the radio to the interface.

I have also "de-filed" a Yaesu SCU-17 interface by drilling a hole in it, and placing a mini toggle switch on it's right side for the same reason.?

Most of us would have likely prefereed to have the Digirig device itself with more INTERNAL options, like pin select, or more importantly a RX pot and a TX pot to adjust levels with a knob. That would have increased the size and the cost of the Digirig.

Does that help explain why some DigiRig owners are struggling to get the proper cable?
One cable (four pins) can NOT do both 1200 and 9600 baud.

Again,? until VARA hit the world,? there was really no reason to? use anything but the "1200 baud" RX audio for everything. (Unless you were doing 9600 baud AX.25 packet.)

?

---

Stephen H. Smith??? wa8lmf (at) aol.com
Skype:??????? WA8LMF
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