RTTY Reference: How to Receive and Send Ham Radio Text

RTTY, short for radioteletype, lets radio stations exchange typed text by switching a signal between two frequency states. A decoder converts those changes into characters on a screen, while an encoder turns outgoing text back into a radio signal. This practical reference covers the connections, starting settings, tuning checks, and operating habits that make RTTY readable.

What an RTTY Text Link Does

An RTTY station needs a radio signal, a way to decode it, and a display for the text. Modern setups commonly use a computer connected to a receiver or transceiver; some radios have decoding and text-entry features built in.

Sending text reverses the process:

Typed characters → encoded signal → transmitter → receiving radio → decoded characters

It resembles texting, but it is not a phone messaging service:

There is no cellular network required. The radio path carries the message.
A normal contact is turn-taking. One station transmits while the other receives.
Classic amateur RTTY does not automatically correct errors. Noise and fading can produce missing or incorrect characters.
The conversation is not private. Other suitably equipped listeners can decode it.

You can begin with reception alone. That lets you learn the software and recognize readable signals before adding transmitter control.

How to Set Up RTTY for Receiving and Sending

Choose the connection method your equipment supports before changing software settings.

Your Goal or Equipment	Connection Needed	Radio Mode to Use
Receive text with a receiver	Receiver audio into the decoder	A suitable sideband or data receive mode
Transmit using audio-frequency shift keying, or AFSK	Computer-generated audio into the transceiver, plus transmit control	The radio’s prescribed mode
Transmit using direct FSK keying	A compatible keying interface into the transceiver’s FSK input	The radio’s FSK/RTTY mode

Step 1: Connect the Radio and Select the Audio Input

Connect the receiver or transceiver to its antenna and establish a usable receive signal.
Install or open software that supports RTTY decoding.
Route the radio’s received audio into the computer. Use an appropriate audio interface.
Select that device as the decoder’s input. Check that the software’s input meter or waterfall responds to the radio.
Keep transmit control disabled during initial receive setup.

For an external audio connection, use an interface appropriate to the radio’s output and computer’s input. A headphone or speaker output can overload an input intended for a much weaker signal.

Raise the receive-audio level enough for a clear display without clipping. If the program is responding to your voice or computer playback instead of the radio, it has the wrong input selected.

Step 2: Set the RTTY Rate and Character Format

Match the decoder to the signal, rather than treating an RTTY preset as universal.

Select the program’s amateur RTTY profile.
Use 45.45 baud binary frequency-shift keying, or FSK, as the common initial setting. This is also the MTTY default implementation documented in a University of Tennessee engineering paper. Confirm the active rate in your software’s RTTY configuration because other profiles and signals can differ.
Select Baudot/ITA2 rather than ASCII when setting up conventional amateur RTTY.
Leave the remaining character-framing options at the software’s amateur RTTY preset unless you know the received station uses something different.

Baud is the signaling rate, not the audio pitch or the speed at which you type. Baudot uses five-bit character codes.

The modulation setting does not, by itself, choose your transmitter connection. An AFSK setup can generate the audio that an SSB transmitter converts into an over-the-air FSK signal.

Step 3: Set the Audio Tones and Frequency Shift

If the decoder requires absolute audio-tone positions, a commonly used low-tone pair is 1275 Hz low and 1445 Hz high. Confirm the selected pair in your decoder or transceiver’s RTTY tone settings; other profiles place the tones elsewhere in the audio passband.
Set the frequency shift to 170 Hz for this common amateur profile. Shift is the separation between the tones, not an additional tone. Confirm it in the decoder or transceiver’s RTTY shift setting.
Make sure the receive filter passes both tone positions.
Keep the decoder’s tone markers within the receiver’s usable audio passband.

These are audio frequencies, not frequencies to enter on the radio’s main tuning dial.

The tone positions and their separation solve different problems. A decoder can have the correct shift yet still miss the signal because its markers are positioned above or below the received tones.

Receiver tuning changes the pitches delivered to the decoder. Consequently, your received audio pitches need not be identical to the audio settings at the transmitting station.

Step 4: Tune a Signal and Get Readable Text

Find an RTTY signal using current amateur band-plan guidance and your receiver’s waterfall or tuning display.
Tune so the signal lines up with the decoder’s mark and space indicators. Depending on the software, you may adjust the receiver, click the signal on the waterfall, or use a tuning control.
Check that both tone positions remain inside the receive filter.
Watch the decoded text through a complete transmission. Look for recognizable words, repeated call signs, and consistent spacing.
If the text remains unreadable, leave transmission disabled while checking audio level, tuning, rate, shift, and polarity.

A filter that is too narrow can remove part of the signal. Heavy noise reduction or other audio processing can also make decoding worse, so begin with a straightforward receive-audio path.

A few accidental letters do not establish that the decoder is working. Consistent text over a sustained transmission is a better test.

Step 5: Configure Outgoing Text and Transmit Control

Before enabling transmission, confirm that your FCC amateur-radio privileges allow RTTY on the selected band and frequency.
Configure the transmit connection selected for your equipment. For AFSK, select the radio-facing audio output; for direct FSK, select the supported keying interface.
Configure push-to-talk control so the program can switch the radio between transmit and receive.
Check whether the program sends characters as you type or holds them until you choose Send.
Clear any old text from the transmit buffer.

With AFSK, route only the intended decoder audio to the radio. System alerts, music, and other computer sounds should not share that transmit path. Use the radio maker’s specified data-audio arrangement rather than microphone speech processing.

Use your own call sign:

CQ CQ DE YOURCALL YOURCALL K

These are operating conventions, not commands that configure the software.

Step 6: Test the Transmitter and Finish in Receive

With the transmitter unkeyed, connect a correctly rated dummy load for a local transmit test.
Keep transmit power and duty cycle within the RTTY or digital-mode limits for the transceiver and any amplifier. RTTY is a sustained transmitting mode; a voice-mode power rating is not a substitute.
Send a brief test message. Confirm that the radio keys correctly and that ending the message returns it to receive.
For AFSK, adjust the level of the radio-facing computer audio while keeping microphone speech processing out of the transmit path. More computer volume is not automatically a better signal.
If an independent receiver or decoder is available, use it to check the transmitted text. Reading the program’s own transmit window does not verify the radio signal.
Unkey the transmitter before reconnecting the antenna. Recheck the radio’s mode and frequency, listen for existing activity, and then make your call.
End your transmission, return to receive, and wait for a reply.

If the software does not release transmit control, stop the test and correct the keying arrangement before operating on the antenna. Finish by clearing queued text and leaving the station in receive.

RTTY Chats, HF Tuning, and Contests

Casual Text Conversations

For a conversational contact, send manageable passages rather than a long prepared essay. Introduce yourself, give the information you want to exchange, and clearly hand the conversation back.

Keep the character set simple. Conventional amateur RTTY is suited to uppercase text, numbers, and supported punctuation, not emoji or modern rich-text formatting.

Once a character has gone over the air, editing your local text cannot reliably erase it from another station’s screen. Send a correction plainly. If you miss something important, ask for that particular item again rather than guessing from partial text.

HF Frequency Readouts

Do not assume that another operator’s displayed frequency is directly comparable to yours. Depending on the radio, mode, and reporting convention, a frequency may refer to a suppressed-carrier dial setting or to the transmitted mark frequency.

When arranging a contact, agree on the band, mode, and frequency convention. Then use the received signal and decoder display to finish tuning, rather than relying on matching dial numbers alone.

Contest Exchanges

RTTY contests commonly use prepared messages, or macros, to send repeatable exchanges quickly. The required exchange comes from that event’s rules; there is no universal contest message.

Before using a macro, inspect its contents and confirm that any automatically inserted information is correct. A wrong call sign or exchange sent perfectly is still wrong.

Do not mistake a busy contest frequency for an invitation to a long conversation. Follow the exchange format in use, and request a repeat when necessary.

Why RTTY Text Is Garbled

Use the symptom to narrow the problem before changing several settings.

Symptom	Likely Cause	First Check or Fix
Radio audio is audible, but the decoder display is blank	Wrong input device or broken audio route	Select the radio’s audio input and verify that its meter responds
Both tone positions are visible, but almost nothing reads correctly	Tuning, rate, shift, or polarity mismatch	Center the signal, verify the profile, then test reverse polarity
Text becomes worse as input volume increases	Audio clipping	Lower the input until clipping stops and check a complete transmission
Characters disappear when a narrow filter is selected	Part of the signal is being filtered out	Widen the passband enough to include both tone positions
Readable words abruptly become numbers or punctuation	A letters/figures shift character was lost	Allow a subsequent shift to restore the character set, then request missing information
Text breaks up during fades or interference	Insufficient signal quality	Retune carefully, reduce local interference, and ask for the affected text again

Reversed Mark and Space

Lower-frequency mark represents “1,” and higher-frequency space represents “0.” That audio ordering is not universal across configurations; sideband selection and interface settings can reverse what reaches the decoder.

When the tones are centered and the other settings match, check the decoder’s polarity setting. The exact label varies by program.

Keep the new setting only if it produces sustained readable text. If it does not, restore the previous setting before testing another cause.

A receive-polarity correction also does not prove your transmit polarity is correct. Verify outgoing text independently before assuming the other station will decode it.

Lost Letters/Figures Shift

Baudot uses five-bit character codes. If noise corrupts a shift character, the decoder can temporarily display the wrong set.

This differs from a rate mismatch: text may read correctly, become a run of implausible symbols, and then recover when another shift arrives.

Keep receiving long enough to see whether the text recovers. Some decoders offer an Unshift on Space option that can help with this behavior, though its usefulness depends on the sending station’s conventions.

How to Check and Save a Working RTTY Setup

A working setup should pass more than a “some letters appeared” test. Before saving the configuration, check that:

Received words and repeated call signs decode consistently.
Both tone positions fit inside the receive passband.
The input level remains below clipping.
A transmit test keys and releases the radio correctly.
An independent reception check produces readable outgoing text.
No unrelated computer audio enters an AFSK transmission.
The program finishes in receive with no unintended text queued.

Save a named software profile and record the radio mode, audio devices, rate, shift, tone placement, receive polarity, and transmit-control method. If you use both AFSK and direct FSK, keep their configurations distinct.

For the next session, start by receiving a recognizable signal and confirming the audio route. Once reception is stable, verify the transmit path before beginning a contact.

Frequently Asked Questions

Can a Technician-Class Operator Use RTTY?

Whether you may transmit depends on the rules that apply to your operation. A Technician-class operator must keep RTTY transmissions within that license’s band and mode privileges under the FCC’s amateur-radio rules. A radio or software menu offering “RTTY” does not establish permission to transmit.

Is RTTY Hard to Learn?

Separate receiving, decoding, and transmitting into individual tasks. Getting readable text first removes much of the uncertainty before you add transmit audio or keying. You do not need to memorize the character codes, but understanding tuning, shift, and polarity makes troubleshooting much easier.

Can an Ordinary Shortwave Radio Decode RTTY?

A shortwave receiver can provide audio to an external RTTY decoder if it has a suitable sideband reception mode and a usable audio output. Built-in text decoding is convenient, but it is not essential.

Can RTTY Carry Weather Information?

Yes. RTTY is among the digital modes used for maritime weather-information exchange, according to the National Weather Service. Identify the service and match its signal parameters before expecting readable text.