Enabling CR/LF in RTTY Software for Real Teletypes

One issue with doing RTTY on a “real” teletype, is that a majority of the RTTY contesters and senders will be using software. As such, some software, such as FLDIGI, default to only sending a single “carriage return” (CR) when you press enter, and not a “line feed” (LF) as well. (In addition, the software may let you type indefinitely, and not insert a CR/LF at the physical limit of real paper, which is often 72 characters).

Fact: Some software like FLDIGI offers an option of sending CR-CR-LF. Why two carriage returns? The first one actually tells the machine to return to the beginning of the line; the second one is just a momentary “pause” to give the actual carriage time to travel back to the start.

Both of these got their names from real teletypes or typewriters; a carriage return tells the print head to go back to the beginning of the line, and line feed tells it to feed one line of paper. With software, this stuff doesn’t matter so much, but without the line feed command, a “real” teletype will simply return to the beginning of the line, and type over top of what’s already there.

(Its even funner on our end; in addition to remember to manually push both RETURN and LINE FEED, we also have to manually press LETTERS or FIGURES depending if we’re typing letters or numbers/punctuation.

This page is intended to be a quick guide on how to enable CR/LF in your RTTY software, so that if you happen to talk to real Teletypes; things will look fine on our end. Leaving these settings set doesn’t hurt anything in normal use either.

FLDIGI as of 4.1.23 (Dec 2022)

  1. Configure > Config Dialog
  2. Expand MODEM
  3. Expand TTY
  4. Expand Tx
  5. Ensure “AutoCRLF” is on, and set to 72 characters
  6. Ensure CR-CR-LF is checked
  7. 2 LTRS? Maybe a new setting? At the bottom it has “LTRS at start”, and mine is set to 2.

Typically this is done to ensure the Teletype/receiver is set to “Letters” mode, as the first one can get lost with a bad signal. Better to send the command twice than to lose the entire subsequent message because the recipient is still in “Figures” (numbers and punctuation) mode.)

Click Save at the bottom, then Close.

(Image updated to Fldigi 4.1.23 control panel in Dec 2022)

MMTTY

It looks like MMTTY enables it by default, but check under the options menu, and ensure you have “Auto Send CR/LF with TX button” enabled

Lastly, check out www.rttycontesting.com for much more information, links to various RTTY programs, and contest information and rules.