FTRX: FT8 Free-Text Reference Extension

Rules
1

Per SOTA rules, an S2S QSO requires exchanging summit references during the contact—and that’s not something standard FT8 supports in a clean, structured way. So here’s my latest endeavor to address/solve this with a simple convention, and I’m going to do it.

FTRX: FT8 Free-Text Reference Extension (v0.4)

FTRX is a lightweight convention to carry a short “reference” (e.g., SOTA/POTA/etc.) using FT8 Free Text, while staying compatible with existing WSJT-X workflows.

This is an application-layer convention only (no FT8 protocol changes).

1. Message Format

Let the transmitted FT8 Free Text be T with length L.

FTRX is defined as:

  • Tail (mandatory): the last 4 characters of T are [DX2][MY2]
  • Reference: everything before the last 4 characters is REF

So:

T = REF + DX2 + MY2

Constraints:

  • L is 5..13
  • REF length is 1..9
  • REF may contain spaces
  • REF may use any character from the FT8 free-text (A-Z 0-9 / + - . ?)
  • DX2 and MY2 are 2-character tags derived from callsigns (see §2)

Parsing note: Because receivers validate based on the last 4 characters, allowing spaces inside REF does not create ambiguity.

2. Callsign Tag Derivation (DX2 / MY2)

To derive the 2-character tag from a callsign:

  1. If the callsign contains /, take the left token as the base call
    • Example: AG6AQ/KH6 → base AG6AQ
  2. DXpedition formatting note: write KH7Z/KH1 (not KH1/KH7Z) so the left-token rule selects the operator call; otherwise the derived tag may be incorrect.
  3. Remove all digits 0–9 from the base call
  4. Take the last 2 characters of what remains
    • If fewer than 2 characters remain, the tag is invalid

3. Validation (Receiver)

A received Free Text T is accepted as valid FTRX only if:

  1. L is 5..13
  2. Extract:
    • DX2 = T[L-4 .. L-3]
    • MY2 = T[L-2 .. L-1]
    • REF = T[0 .. L-5] (length 1..9)
  3. Compute:
    • DX2_expected from the other station’s callsign
    • MY2_expected from my callsign
  4. Require exact match:
    • DX2 == DX2_expected and
    • MY2 == MY2_expected

If any check fails, treat it as ordinary Free Text.

4. Semantics

FTRX is only used as a sign-off equivalent.

  • FTRX may replace whichever sign-off message is appropriate for my station at that step:
    • RR73 or
    • 73

Conceptually:

FTRX = (RR73 or 73, whichever I should send now) + reference REF

Only one reference should be sent per QSO per station.

5. Mini-FT8 Sequence Adaptation

Mini-FT8 integrates FTRX with two user settings for backward compatibility with WSJT-X.

5.1 Settings

  • Ref (string)
    • length 1..9 (empty disables)
    • spaces allowed
  • Send_Ref (enum): 0 | 1 | 2
    • 0: do not send FTRX
    • 1: replace one sign-off (RR73 or 73) with FTRX
    • 2: replace up to two sign-offs with FTRX

5.2 Rule

When Mini-FT8 is about to transmit a sign-off (RR73 or 73):

  • If Send_Ref > 0, Ref is set, and ref_tx_count < Send_Ref:
    • transmit T = Ref + DX2 + MY2 (FTRX)
    • increment ref_tx_count
  • Else:
    • transmit the normal sign-off message (RR73 / 73) per standard FT8 sequencing

5.3 Fallback

After 1–2 FTRX attempts (per Send_Ref), if the other station does not converge cleanly, Mini-FT8 falls back to normal sign-off messages to complete the QSO in standard WSJT-X style.

6. Examples (AG6AQ at W6/CC-052, N6HAN at W6/CC-072)

Tags (digits removed, last 2 chars):

  • AG6AQ → AQ
  • N6HAN → AN

Example A: AG6AQ sends FTRX as final sign-off

  • N6HAN → AG6AQ N6HAN -10
  • AG6AQ → N6HAN AG6AQ R-12
  • N6HAN → AG6AQ N6HAN RR73
  • AG6AQ → W6/CC-052ANAQ (FTRX replaces AG6AQ’s sign-off here)

Example B: N6HAN sends FTRX as sign-off (replacing RR73)

  • N6HAN → AG6AQ N6HAN -10
  • AG6AQ → N6HAN AG6AQ R-12
  • N6HAN → W6/CC-072AQAN (FTRX replaces N6HAN’s RR73)
  • AG6AQ → W6/CC-052ANAQ (or N6HAN AG6AQ 73)

Example C: Allowing spaces in REF

  • … report exchange …
  • N6HAN → W6/CC072 AQAN (REF contains a space; tail is still AQAN)
  • AG6AQ → W6/CC052 ANAQ (or normal 73)
  • done

Notes / Non-goals

  • FTRX does not attempt to standardize reference namespaces (SOTA vs POTA, etc.) beyond “up to 9 characters”.
  • FTRX is designed to be robust and backward compatible: stations that do not implement it will simply see Free Text.
1 Like
2

I don’t think so. Can you find the rule that says that? I can’t find any rules about Summit to Summit contacts.

3

You’re right. I just re-visited SOTA rules, it’s “strongly recommended”, but not mandatory:

… QSOs must comprise an exchange of callsigns and signal reports; it is strongly recommended that the summit identifier be given during each contact. Where the summit identifier is not given in each contact (for example in slow CW QSOs) it should be repeated frequently every few QSOs. Note: Summits are commonly mis-identified by chasers when
‘spotting’ on the SOTA Reflector…