Digital Modes Beyond FT8: FT4, JS8Call, PSK31 and RTTY Compared
FT8 Won the Popularity Contest, Not the Whole Argument
If you tune around the digital segments of an HF band on a busy day, most of what you see on the waterfall is FT8. It earned its dominance honestly: it decodes signals well below the audible noise, it is easy to set up and it makes a lot of contacts with very little effort. But FT8 is designed for a specific job, which is exchanging a minimal, structured message with a station you can barely hear. If you want to type a sentence, run a contest at speed, hold a conversation or copy a signal without a computer clock synchronised to the second, other digital modes do the job better.
This article compares the modes most operators meet after FT8: FT4, JS8Call, PSK31, RTTY and the specialised weak-signal modes bundled with WSJT-X. It focuses on what each mode is for and how to choose. Specific operating frequencies are deliberately omitted, because they differ between IARU regions and countries and change over time; check the current IARU Region 1 band plans or your own national regulator’s rules, or the ARRL’s overview of digital modes if you operate in Region 2.
Two Families of Digital Modes
It helps to sort digital modes into two families before comparing them individually. The first family uses structured, time-synchronised messages: FT8, FT4 and the other WSJT-X modes transmit in fixed time slots with tightly defined message formats, and rely on forward error correction and long integration to pull signals out of noise. Both stations must have accurate computer clocks. The second family uses continuous, unsynchronised transmission of keyboard text: PSK31, RTTY and their relatives send whatever you type as you type it, with no rigid time slots, so you can have an open-ended chat without agreeing on timing.
JS8Call sits between them. It borrows the weak-signal engineering of FT8 but wraps it in a messaging layer that supports free-form text, directed messages and relaying. That is why it appeals to operators who like FT8’s sensitivity but want to say more than a signal report.
FT4: FT8’s Faster Sibling for Contests
FT4 comes from the same development team as FT8 and is distributed with the same WSJT-X program. Its transmit and receive periods are considerably shorter than those of FT8, so a contact completes in less time, and it is designed with contesting in mind. The trade-off is sensitivity: a shorter transmission gives up some of the raw weak-signal performance that makes FT8 so remarkable, so FT4 works best when signals are reasonably strong and the goal is rate, not survival at the edge of the noise.
FT4 also has dedicated contest exchange handling in WSJT-X, which is why it shows up in digital contest weekends. If you want to understand how contest thinking transfers to a digital mode, our article on where contest rate really comes from covers the run-versus-search-and-pounce tradeoffs that apply equally to a keyboard mode. Operators moving between the two programs will also find our comparison of JTDX versus WSJT-X useful, since both decoders handle the same family of modes with different priorities.
When FT4 Makes Sense
Choose FT4 when propagation is decent, the band is crowded and you want more contacts per hour. Avoid it when the band is marginal and you are chasing a rare station at the edge of readability; FT8 is the better tool for that.
JS8Call: Conversation and Relay on a Weak-Signal Engine
JS8Call is a separate program that uses a modulation derived from FT8 but adds a keyboard-to-keyboard messaging system. You can send free text, address messages to a specific callsign, request a station’s signal report or status and even relay a message through a third station that hears both ends. It offers several speed settings that trade transmission time against sensitivity, so a station can choose a faster setting when conditions are good and a slower one when they are poor.
The strengths are obvious: sensitivity close to the weak-signal family, real conversation, and the ability to operate with a very modest station. The costs are equally clear. Messages are slow to compose and send compared with a mode that handles a fixed exchange automatically, the mode is not aimed at contests and the design assumes you are sitting at the screen because a message needs a human to write it. JS8Call is particularly popular with emergency-communications enthusiasts and portable operators who want to pass short messages when infrastructure is unavailable.
PSK31: The Keyboard Mode That Still Works
PSK31 was a breakthrough when it appeared: a narrow-bandwidth phase-shift keyed mode that allowed keyboard chat with a modest transmitter and soundcard interface. It is still in use, usually with fldigi or a similar multimode program. A PSK31 signal is a narrow, steady trace on the waterfall, and the mode works well for casual conversation when conditions are decent.
Its limitations are equally well understood. It has no time-slot discipline, so any station can call at any time, which makes it a good conversational mode but a poor one for weak-signal work or heavy crowding. It is also more sensitive than an unprocessed voice signal, but not in the same league as the modern structured modes. PSK31 remains a good choice if you like keyboard chat on a quiet band, want a mode that needs no precise clock and enjoy the human rhythm of a live text conversation.
RTTY: The Contest Veteran
Radioteletype is among the oldest digital modes, and it is still one of the most competitive contest modes. It uses two-tone frequency-shift keying with a traditional baud rate and shift, and decoders in logging and multimode programs handle it well. Its appeal in contesting is speed and simplicity: exchanges are short, decoding is fast, and operators can work a big pileup at a good rate. Several major contests include RTTY sections; check the current rules for each event, because categories and scoring change.
The trade-offs are that RTTY is more fragile than modern coded modes: it needs a decent signal, the decoder can be fooled by selective fading and it takes up more bandwidth than PSK31. Operators drawn to RTTY contesting usually invest in a good decoder and a well-filtered receiver, and, as always, in a clean station that does not splatter. Our guide to choosing a contest logger explains how the major loggers integrate RTTY decoding and keying.
WSJT-X’s Specialist Modes
WSJT-X includes more than FT8 and FT4. Its family covers several purpose-built modes: WSPR, a beacon-style mode for measuring propagation with tiny power; modes for meteor-scatter and for extremely weak VHF and EME signals; and modes tuned for very low frequencies. Each is optimised for a narrow application and is worth exploring if you enjoy experimenting. Read the program’s documentation for the current mode list and details, because the set of modes and their parameters change between releases. Our walk-through of a WSJT-X and FT8 setup that works the first time covers the configuration steps that apply to all of them: correct time, correct audio levels and correct rig control.
Side-by-Side Comparison
| Mode | Style | Timing | Weak-signal strength | Best for | Main drawback |
|---|---|---|---|---|---|
| FT8 | Structured, fixed message | Time-slotted, needs accurate clock | Excellent | DX and casual contacts in poor conditions | Minimal exchange, crowded segments |
| FT4 | Structured, fixed message | Time-slotted with shorter cycles | Good but below FT8 | Contests and fast contacts on decent bands | Less sensitive than FT8 |
| JS8Call | Free text and directed messages | Time-slotted with selectable speeds | Very good on slower settings | Conversation and relayed messages with weak signals | Slow and manual, not for contests |
| PSK31 | Keyboard chat | Continuous, no clock needed | Moderate | Casual chat on quiet bands | Struggles in crowded or weak conditions |
| RTTY | Keyboard text | Continuous, no clock needed | Modest | Contest rate and traditional operating | Fragile under fading, wider signal |
Choosing a Mode by Goal
You want the most contacts with the least effort. Stay with FT8, or use FT4 during a contest weekend. You want to talk. Try PSK31 for conversation on a decent band or JS8Call when signals are weak. You want to contest with a keyboard mode. RTTY is the traditional choice; FT4 is the modern alternative. You want to experiment with propagation. Explore WSPR and the specialised WSJT-X modes, and combine their results with the propagation data in our article on VOACAP and prediction tools.
Watch Out for the Practicalities
Whatever mode you pick, three things determine success. First, audio levels: overdriving the transmit audio produces a wide, dirty signal that annoys everyone on the band and reduces your own decode rate. Keep the ALC reading minimal and the power reduced, especially on modes that key the transmitter continuously. Second, time: any time-slotted mode needs your computer clock to be accurate, and a drifting clock is the most common reason for zero decodes. Third, logging: digital contacts can generate thousands of log entries, and it pays to know how your logger exchanges data with others. Our explainer on ADIF and moving your log between programs covers what happens when you export and import.
What You Need to Get Started With Any of Them
The good news is that the station requirements are almost identical across these modes. You need an SSB-capable transceiver, a computer, and an audio path between the two: either the radio’s built-in USB sound interface or an external interface. You also need rig control or a push-to-talk method so the software can key the transmitter, and a way to keep the computer clock accurate if you plan to use any time-slotted mode. If you have already configured a program for FT8, you have done most of the work; a second program such as JS8Call or fldigi mostly needs its own audio device and radio selections pointing at the same hardware. Our guide to rig control with Hamlib explains how software and radio talk to each other.
A Sensible Learning Path
Do not try to learn everything at once. Spend a week on FT4 to see how a faster exchange feels compared with FT8. Then try one keyboard mode, either PSK31 for a relaxed chat or RTTY if you have a contest in mind, and listen on the waterfall before you transmit so you learn what a healthy signal looks like. Add JS8Call only when you have a reason to send free text. Each mode teaches a different lesson about audio levels, timing and courtesy, and skills learned on one carry over to the others.
Keeping Your Signal Clean Across Modes
All of these modes pass through the same audio chain, so the same faults show up everywhere: a mic-gain setting that is too high, a compressor left on, an ALC meter that moves during transmit. Turn off speech processing, reduce drive until ALC barely moves and check your signal with a second receiver or a web-based receiver if you can. A clean signal is the cheapest performance upgrade in digital operating.
Bandwidth and Etiquette
Digital signals share segments of the band with each other, and courtesy matters. Do not transmit on top of an existing signal, keep power modest, stay within the segment your band plan reserves and remember that FT8-style modes have popular calling areas that fill up. If you use a mode that transmits continuously, check the frequency for a moment before calling, because you cannot hear a weak QSO in progress on a waterfall the way you can on voice. Band plans are recommendations in many places and rules in others, so consult the plan for your region before choosing where to operate.
Frequently Asked Questions
Is FT4 better than FT8?
Neither is better in general. FT4 completes contacts faster and is designed for contests, while FT8 is more sensitive and better for weak signals and DX in poor conditions.
Do I need an accurate clock for PSK31 and RTTY?
No. These continuous modes are not time-slotted, so precise clock synchronisation is not required, unlike FT8, FT4 and JS8Call.
What is JS8Call used for?
JS8Call combines FT8-style weak-signal performance with free-text messaging, directed messages and relaying, which makes it popular for conversation and for emergency-communications practice.
Which digital mode is best for contests?
RTTY is the traditional keyboard contest mode and FT4 is the modern structured alternative. Check the rules of each contest, because modes, categories and exchanges differ.
Which program should I use for PSK31 and RTTY?
A multimode program such as fldigi, or the built-in decoders in many contest loggers, handles both modes. Choose according to your operating style and whether you also need logging integration.
Are digital mode frequencies the same worldwide?
No. Band plans differ between IARU regions and countries, so always consult the current plan for your region and your national rules.
Do these modes work with low power?
Yes, the weak-signal modes in particular are popular with low-power and portable operators, but keep the transmit audio clean and reduce power on modes that key continuously.
The Bottom Line
FT8 is a superb tool but it is one tool. FT4 trades some sensitivity for speed, which suits contests and busy bands. JS8Call adds conversation and relaying to a weak-signal engine. PSK31 offers relaxed keyboard chat without a clock, and RTTY remains a contest-proven workhorse. Pick the mode that matches the job, keep audio clean and time accurate, and check your regional band plan before you transmit. Explore more operating guides in the LY4A blog and the tag index.