I've recently learned about these additions to the WSJTx.

 You can stop reading here if you have no interest.

Short version: WSJT team is creating a version of FTx that sends any message of any length that you want.

Long version:

A problem with the WSJT message types (FT4, FT8, FST4, Q65, MSK144) are that they can't send an arbitrary message (any text message and length that you want).

RTTY and PSK can send any text that you want (with the new radios it is trivial to send/receive RTTY, the tuning is shown and the radio itself decodes the messages) but they are slow and create (compared to WSJT) large messages.

The WSJT team is creating a version of FTx that sends any message you want, it's called JRTTY.

The description below is from the Google AI

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JTTY is an upcoming digital protocol being developed by the WSJT-X development team, the same group behind FT8 and JT65. Its goal is to provide the familiar keyboard-to-keyboard chat and fast contest feel of traditional RTTY, but with vastly improved weak-signal performance and a significantly lower error rate. [1, 2, 3]
While standard RTTY is a legacy mode most often seen during organized contests like the ARRL RTTY Roundup, JTTY is aimed at bringing modern, efficient signal processing to that conversational and contesting style. [1, 2, 3]
What to Know About JTTY:
You can track the development and release of JTTY by checking the WSJT-X GitHub Repository or the WSJT-X Development Pages. [1]
Special & Enhanced Message Types
These types are reserved for non-standard callsigns, contests, and specific activities:
  • Type 6: Arbitrary Text / Telemetry. Allows for custom alphanumeric messages up to 13 characters (e.g., W1AW GIVING 73).
  • Type 7: Compound Call Signs. Encodes non-standard prefixes/suffixes (e.g., /P, /R, or DXpedition formats).
  • Type 8: DXpedition / Fox & Hounds Format. Used specifically for rare DX stations managing heavy pileups.
  • Type 9: Contest Exchanges. Sends brief report codes or serial numbers depending on the specific contest (e.g., ARRL Field Day).
  • Type 10: QSY / Message System. Used to command or request a QSY (frequency change). [1, 2, 3, 4, 5]
For a complete look at bit-field structures, check out the FT4/FT8 QEX Article or review the protocol specifications in the WSJT-X User Guide. [1]
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More details on FTx:
Standard Message Types (FT4, FT8, FST4, Q65, MSK144)
These types are used for everyday contacts: [1, 2]
  • Type 0: Standard QSO (e.g., CQ W1AW FN42). Used for directional CQs and standard callsign exchanges.
  • Type 1: Grid Locator Exchange (e.g., W1AW K1JT FN42). Used to send your Maidenhead Grid Square.
  • Type 2: Signal Report (e.g., K1JT W1AW -15). Used to exchange signal-to-noise ratios (SNR).
  • Type 3: Acknowledgment (e.g., W1AW K1JT R-15). Sending a Roger (R) along with the signal report.
  • Type 4: Roger-Roger-Roger (e.g., K1JT W1AW RR73). Indicates all previous reports have been received successfully.
  • Type 5: 73 (e.g., W1AW K1JT 73). Used to end the contact formally. [1, 2, 3, 4, 5]
If you stuck with reading this to here, thanks!
I'm particularly interested in the RTTY part, I operate RTTY contests because they are so easy with an IC-7610 and I had a teletype machine in the late 1960's & early '70s. Some other guys in my town and my age had them, we built Terminal Units (modems but not called that then) and used it on 2m AM with <10W crystal controlled radios that Civil Defense gave us for our emergency work.
73, Rich wb4ehg