Q Codes · ITU International Radio Abbreviations · Ham Radio
All 57 ITU Q codes used in ham radio and CW operation. Every code has a question form, answer form, Morse audio, usage examples, and a searchable reference table. The complete Q code guide for beginners and licensed operators.
Q codes are three-letter abbreviations starting with Q, standardized by the ITU (International Telecommunication Union). Each code has a question form ("Are you busy?") and a statement form ("I am busy"). They began in maritime telegraphy in 1912 and remain essential in ham radio CW to this day. Search below or filter by category.
| Code | Question Form | Answer / Statement | Morse | Category | Play |
|---|---|---|---|---|---|
| QRA | What is your station name? | Name of my station is… | --.- .-. .- | Operating | |
| QRB | How far are you from my station? | Distance is… km | --.- .-. -... | Operating | |
| QRG | Tell me my exact frequency | Your frequency is… kHz | --.- .-. --. | Frequency | |
| QRH | Does my frequency vary? | Your frequency varies | --.- .-. .... | Frequency | |
| QRI | How is the tone of my transmission? | Tone is… (1=Good 2=Variable 3=Bad) | --.- .-. .. | Signal | |
| QRK | What is the readability of my signals? | Readability is… (1–5) | --.- .-. -.- | Signal | |
| QRL | Are you busy / is frequency in use? | I am busy / frequency is in use | --.- .-. .-.. | Operating | |
| QRM common | Is my transmission being interfered with? | Man-made interference (1–5) | --.- .-. -- | Signal | |
| QRN common | Are you troubled by static? | Natural static (1–5) | --.- .-. -. | Signal | |
| QRO | Shall I increase power? | Increase transmitter power | --.- .-. --- | Operating | |
| QRP common | Shall I decrease power? | Low power operation (≤5W) | --.- .-. .--. | Operating | |
| QRQ | Shall I send faster? | Send faster (… wpm) | --.- .-. --.- | Operating | |
| QRS common | Shall I send more slowly? | Send slowly (… wpm) | --.- .-. ... | Operating | |
| QRT common | Shall I stop sending? | Stop sending / going off air | --.- .-. - | Operating | |
| QRU | Have you anything for me? | Nothing for you | --.- .-. ..- | Traffic | |
| QRV common | Are you ready? | I am ready | --.- .-. ...- | Operating | |
| QRX common | When will you call again? | Will call at… hours on… kHz | --.- .-. -..- | Operating | |
| QRZ common | Who is calling me? | You are being called by… | --.- .-. --.. | Operating | |
| QSA | What is the strength of my signals? | Strength is… (1–5) | --.- ... .- | Signal | |
| QSB common | Are my signals fading? | Your signals are fading | --.- ... -... | Signal | |
| QSD | Is my keying defective? | Your keying is defective | --.- ... -.. | Signal | |
| QSK common | Can you hear between your signals? | I can hear between signals (full QSK) | --.- ... -.- | Operating | |
| QSL common | Can you acknowledge receipt? | I acknowledge receipt | --.- ... .-.. | Traffic | |
| QSO common | Can you communicate with…? | I can communicate / radio contact | --.- ... --- | Traffic | |
| QSP | Will you relay to…? | I will relay to… | --.- ... .--. | Traffic | |
| QST | General call to all stations | General bulletin follows | --.- ... - | Traffic | |
| QSY common | Shall I change to another frequency? | Change to… kHz | --.- ... -.-- | Frequency | |
| QSZ | Shall I send each word twice? | Send each word twice | --.- ... --.. | Traffic | |
| QTC | How many messages to send? | I have… messages for you | --.- - -.-. | Traffic | |
| QTH common | What is your location? | My location is… | --.- - .... | Location | |
| QTR common | What is the correct time? | The time is… | --.- - .-. | Location | |
| QRD | Where are you going and where from? | Going to… from… | --.- .-. -.. | Location | |
| QRE | What is your estimated arrival time? | ETA is… | --.- .-. . | Location | |
| QSG | Shall I send… messages at a time? | Send… messages at a time | --.- ... --. | Traffic | |
| QSM | Shall I repeat the last message? | Repeat the last message | --.- ... -- | Traffic | |
| QSN | Did you hear me on… kHz? | Heard you on… kHz | --.- ... -. | Frequency | |
| QSS | What working frequency will you use? | Will use… kHz | --.- ... ... | Frequency | |
| QSU | Shall I reply on… kHz? | Reply on… kHz | --.- ... ..- | Frequency | |
| QSW | Will you send on… kHz? | Will send on… kHz | --.- ... .-- | Frequency | |
| QSX | Will you listen on… kHz? | Listening on… kHz | --.- ... -..- | Frequency | |
| QSR | Shall I repeat the call on… kHz? | Repeat call on… kHz | --.- ... .-. | Frequency | |
| QTA | Shall I cancel message number…? | Cancel message number… | --.- - .- | Traffic | |
| QTB | Do you agree with my word count? | I do not agree with your count | --.- - -... | Traffic | |
| QTS | Will you send your call for tuning? | Sending call for tuning | --.- - ... | Operating | |
| QTX | Will you keep your station open? | Keeping station open until… | --.- - -..- | Operating | |
| QUA | Have you news of…? | News of… is… | --.- ..- .- | Misc | |
| QUC | What is the number of last message received? | Number of last message is… | --.- ..- -.-. | Traffic | |
| QUD | Have you received urgency signal? | Received urgency signal | --.- ..- -.. | Misc | |
| QUE | Can you speak in… language? | I can speak in… | --.- ..- . | Misc | |
| QUF | Have you received distress signal? | Received distress signal | --.- ..- ..-. | Misc | |
| QRC | Who settles your station accounts? | Accounts settled by… | --.- .-. -.-. | Misc | |
| QRF | Are you returning to…? | Returning to… | --.- .-. ..-. | Misc | |
| QRJ | How many calls do you receive? | I receive… calls per hour | --.- .-. .--- | Signal | |
| QRW | Shall I inform… you are calling? | Please inform… you are calling | --.- .-. .-- | Operating | |
| QRY | What is my turn? | Your turn is… (number) | --.- .-. -.-- | Operating |
All 57 Q codes fall into six practical groups. Understanding which group a code belongs to tells you its purpose before you even know the specific meaning. Click any pill to hear that Q code in Morse.
Codes for describing signal strength, readability, tone, fading, interference, and keying quality. Most use the 1–5 scale (RS scale). QRM and QRN are the most frequently heard.
Codes for negotiating operating frequency — what frequency to use, whether it varies, whether to change. QSY is the most common: "let's move to another frequency."
The backbone of CW operating procedure. QRZ (who's calling), QRV (ready), QRT (stop/off air), QRP (low power), QSK (full break-in). Every CW operator uses these daily.
Message handling and contact codes. QSO is any radio contact. QSL confirms it. QTC carries messages. QST is ARRL's bulletin call. These define the structure of formal traffic nets.
QTH (location) and QTR (time) are among the most used Q codes in any contact. QRD and QRE cover destination and ETA for maritime and aviation use.
Rarely used codes for station accounts, distress acknowledgement, language capability, and general news. QUE is useful for multilingual contacts.
The 20 Q codes every CW operator needs to know. Each section is individually linkable — e.g. /morse-code-q-codes/#qcs-QTH. Click ▶ Play to hear the code in Morse.
? = What is your location?
= My location is… (city, grid square, coordinates)
QTH is one of the first Q codes every new ham learns. In CW contacts it replaces "where are you located?" In modern use operators give city, state/country, or Maidenhead grid square (e.g. FN31). On digital modes, QTH is still used universally.
? = Can you acknowledge receipt?
= I acknowledge receipt
QSL means "confirmed." In CW it confirms you received the other station's transmission. The famous QSL card — a postcard confirming a radio contact — takes its name from this code. Millions are exchanged annually by ham operators worldwide as proof of contact.
? = Can you communicate with…?
= I can communicate / a two-way contact
A QSO is any completed two-way contact between stations. Operators log QSOs in their station log with date, time, frequency, mode, and signal reports. "I had a great QSO with Japan last night" means a successful contact was made.
? = Who is calling me?
= You are being called by…
QRZ is sent when a station hears a call but cannot identify the caller — usually due to QRM or weak signal. It means "repeat your callsign, I didn't copy it." QRZ.com, the world's largest ham radio callsign database, takes its name from this code.
? = Is my transmission being interfered with?
= Man-made interference level (1=nil 2=slight 3=moderate 4=severe 5=extreme)
QRM covers interference from other radio stations, electrical equipment, or digital noise. The number suffix (QRM 3) rates severity. QRM differs from QRN: QRM is man-made, QRN is natural. "QRM from a nearby station" is extremely common in CW operation.
? = Are you troubled by static?
= Natural static level (1–5)
QRN covers atmospheric noise — lightning crashes, precipitation static, auroral noise. Summer thunderstorm seasons drive QRN levels high on low bands. The distinction from QRM matters: QRN is weather-dependent and affects low frequencies more than high.
? = Shall I decrease transmitter power?
= Decrease power / operating with low power (≤5W)
QRP has become shorthand for the entire low-power operating movement. QRP operators run 5 watts or less, often making contacts across continents. The QRP community is one of the most active in amateur radio, with clubs, contests, and dedicated frequencies worldwide.
? = Are you ready?
= I am ready
QRV confirms the station is on frequency, tuned up, and ready to copy. It answers the implicit question before a contact begins. A station calling "QRV?" is asking if the other end is listening and prepared to proceed.
? = Shall I stop sending?
= Stop sending / going off air
QRT means the station is closing down. "Going QRT" means going off air for the session. Unlike SK (which ends a contact), QRT ends the entire operating session. Often paired with the time: "QRT 1800Z."
? = When will you call again?
= I will call you again at… hours on… kHz
QRX tells the other station to wait — the operator will return at a specified time or frequency. Similar to the prosign AS but more specific: QRX 10 means "stand by 10 minutes." Commonly used when a station needs to attend to something briefly.
? = Are my signals fading?
= Your signals are fading
QSB describes the rise and fall of signal strength caused by ionospheric propagation changes. Deep QSB can make a strong signal disappear entirely for seconds. Common on HF bands, especially during changing band conditions at dawn and dusk.
? = Can you hear me between your signals?
= I can hear between my own signals (full QSK)
QSK (full break-in) means the transmitter switches to receive between every dit and dah, allowing the other operator to interrupt at any moment. It is the most conversational CW style. The opposite is semi-break-in (QSK off) where the station listens only between words.
? = Shall I change to another frequency?
= Change to… kHz
QSY is the standard way to move a contact off a busy calling frequency to a working frequency. "QSY 14.025" means move to 14.025 MHz. After contact, QSY keeps calling frequencies clear for others.
? = Are you busy / is this frequency in use?
= I am busy / this frequency is in use
Before transmitting on any CW frequency, good operating practice requires sending "QRL?" to check if the frequency is in use. If someone replies "QRL" (yes, busy) you must move on. Skipping this check is a major operating error that causes interference.
? = Shall I send more slowly?
= Send more slowly (… wpm)
QRS is one of the most beginner-friendly codes — it politely asks the other operator to slow down. No CW operator should feel embarrassed sending QRS. Experienced operators always honour QRS requests graciously.
? = Shall I increase transmitter power?
= Increase transmitter power / high power station
QRO is the opposite of QRP — it describes high-power operation (typically above 100W, often up to the legal limit of 1500W in the US). "QRO station" implies a well-equipped station with amplifier. Sometimes used informally to contrast with the QRP movement.
? = How many messages do you have to send?
= I have … messages for you
QTC is the core of formal traffic net operation. "QTC 3" means "I have 3 messages to pass to you." Traffic nets move formal written messages (radiograms) between operators and ultimately to recipients, often serving as an emergency communications backbone.
? = What is the correct time?
= The time is … (UTC)
QTR exchanges UTC (Coordinated Universal Time). Ham radio uses UTC universally to avoid time zone confusion in international contacts. WWV and WWVH broadcast accurate time signals specifically for this purpose. QTR is still used in formal nets and message handling.
= General call to all stations — bulletin follows
= All stations: a general message is about to be sent
QST precedes a general bulletin meant for all stations on frequency. The ARRL (American Radio Relay League) publishes its flagship magazine named QST, taken from this code. On air, "QST DE W1AW" means the ARRL station is about to transmit a bulletin for all hams.
? = Will you tell me my exact frequency?
= Your exact frequency is … kHz
QRG is used to verify an operating frequency, especially when a station may be slightly off frequency. In contest operation, knowing your exact frequency helps avoid inadvertent interference. Spectrum analysers have reduced QRG use but it remains standard in formal nets.
? = What is the name of your station?
= The name of my station is…
QRA asks for the formal station name or callsign identifier. Used in formal traffic and maritime communication where the full station designation is required, not just a callsign. In modern ham radio, the callsign itself serves this purpose.
? = How far are you from my station?
= The distance is approximately… km
QRB asks for the distance between stations — useful in maritime navigation, direction finding, and emergency communication. In ham radio, operators often share QRB when making unusual or long-distance contacts. The distance is given in kilometres.
? = By whom are your accounts settled?
= My accounts are settled by…
QRC is a legacy commercial telegraphy code used to identify the party responsible for billing. It originated when stations charged per-message fees in maritime and commercial communication. Rarely used in modern amateur radio but retained in the ITU standard.
? = Where are you bound and where are you from?
= I am bound for… and coming from…
QRD is primarily a maritime and aeronautical code for voyage information. It gives both the destination and point of departure. Used by coast guard and vessel traffic services to track ship movements. In emergency communications it can convey movement plans.
? = What is your estimated time of arrival?
= My ETA is… at…
QRE provides an estimated time of arrival at a specified point. Used in maritime, aeronautical, and emergency communications to coordinate rendezvous and resource planning. Time is always given in UTC. In emergency nets, QRE helps coordinate rescue asset deployment.
? = Are you returning to…?
= I am returning to…
QRF indicates a vessel or aircraft is returning to a previously held course or position. Used in maritime and aeronautical control to confirm a course correction or return to base. Rarely heard in amateur radio operation today.
? = Does my frequency vary?
= Your frequency varies
QRH is sent when a station's transmit frequency is drifting or unstable — caused by an oscillator warming up, power supply issues, or poor temperature compensation. On vintage equipment QRH was common during warm-up periods. Modern synthesized radios rarely suffer from QRH.
? = How is the tone of my transmission?
= The tone is… (1=Good 2=Variable 3=Bad)
QRI rates the audio quality of a CW signal on a three-point scale. A QRI 1 (good) tone is clear and stable. QRI 2 (variable) may have modulation or ripple. QRI 3 (bad) is rough, buzzy, or chirpy. Poor tone often indicates power supply issues, key clicks, or chirp in older transmitters.
? = How many calls are you receiving?
= I am receiving… calls per hour
QRJ was used in commercial telegraphy to report traffic volume. It helped supervisors allocate operators during peak periods. In modern amateur operation it is rarely used, though contest operators informally note rate (contacts per hour) which serves the same purpose.
? = What is the readability of my signals?
= Readability is… (1=Unreadable 5=Perfectly readable)
QRK is the readability component of the RST signal report. In CW, readability (R) is rated 1–5 on how well copy can be made. QRK 5 means every character is copied. QRK 1 means signals are present but no copy is possible. Combined with QSA (strength), it gives a complete signal picture.
? = Shall I send faster?
= Send faster (… words per minute)
QRQ is the opposite of QRS — it asks the other station to increase sending speed. Used when an operator is comfortable copying at higher speed and the other station is sending unnecessarily slowly. High-speed CW operators sometimes use QRQ to invite faster exchange during contests.
? = Have you anything for me?
= I have nothing for you
QRU tells a calling station there is no traffic waiting for them. In formal traffic nets, stations check in asking QRU? — is there any message traffic waiting? The net control replies QRU (nothing) or gives the traffic count. A clean reply means the station can proceed or sign off.
? = Shall I inform… that you are calling on… kHz?
= Please inform… that I am calling on… kHz
QRW asks a third station to relay a calling notice — "please tell W1AW I'm calling on 14.025." Used when a station cannot reach its target directly but can reach a relay. In modern ham radio with internet-linked systems, QRW is rarely needed but remains in the ITU standard.
? = What is my turn?
= Your turn is number… (sequence number)
QRY provides a queue position to a station waiting to transmit — used in formal multi-station nets or coordinated maritime communications. "QRY 3" means you are third in the queue. In busy emergency nets, QRY helps maintain orderly access to the frequency.
? = What is the strength of my signals?
= Signal strength is… (1=Scarcely perceptible 5=Extremely strong)
QSA is the strength component of the RS signal report. Scale: 1=scarcely perceptible, 2=weak, 3=fairly good, 4=good, 5=very good. Combined with QRK (readability), QSA gives the full signal picture. In modern ham radio the RST system (1–5, 1–9, 1–9) has largely replaced QSA/QRK in casual contacts.
? = Is my keying defective?
= Your keying is defective
QSD alerts an operator that their keying has problems — broken characters, incorrect dit/dah ratio, key clicks, or incomplete characters. Common causes include a sticky key contact, incorrect keyer settings, or RF getting into the keyer circuitry. Politely sending QSD is a favour to any operator.
? = Shall I send… messages at a time?
= Send… messages at a time
QSG regulates message batching in formal traffic nets. "QSG 5" means send five messages in sequence before pausing for acknowledgement. Used in high-volume traffic sessions to improve efficiency — rather than acknowledging each message individually, the receiving station confirms the whole batch.
? = Shall I repeat the last message sent?
= Repeat the last message (or message number…)
QSM requests a retransmission of the preceding message — used when copy was incomplete due to QRM, QRN, or a momentary lapse in concentration. Unlike "AGN?" (again, please repeat) which requests general repetition, QSM specifically requests the formal last message in a traffic sequence.
? = Did you hear me on… kHz?
= I heard you on… kHz
QSN confirms which frequency a station was heard on. Used when a station transmits on one frequency while listening on another (split operation). Confirming the transmit frequency prevents confusion in split-frequency DX pileups where the DX station listens up or down from its transmit frequency.
? = Will you relay to…?
= I will relay to… free of charge
QSP requests or confirms message relay through a third station. It is fundamental to traffic net operation — messages are passed from station to station (each saying QSP) until they reach a station close to the final recipient. The phrase "free of charge" echoes QSP's commercial telegraphy origins.
? = Shall I repeat the call on the calling frequency?
= Repeat your call on… kHz
QSR directs a station to repeat its call on the designated calling frequency so other stations can also hear it. Used in maritime and aeronautical communication to broadcast a vessel's position or call to all stations simultaneously. Ensures awareness is not limited to the direct contact.
? = What working frequency will you use?
= I will use… kHz as working frequency
QSS establishes the working frequency for a contact after initial exchange on the calling frequency. Similar to QSY but specifically names the agreed working frequency rather than requesting a move. Used in formal maritime and traffic net procedures to confirm the frequency both parties will use.
? = Shall I reply on this frequency or on… kHz?
= Reply on this frequency or on… kHz
QSU directs the receiving station where to transmit its reply — on the current frequency or a specified alternative. Used in simplex and duplex arrangements where the listening and transmitting frequencies differ. Ensures both stations are aligned before the reply is sent.
? = Will you send on… kHz?
= I will send on… kHz
QSW confirms a station's transmit frequency — complementing QSX (listen frequency) in split-frequency operation. In DX pileup management, the DX station sends QSW (my transmit frequency) and QSX (where I'm listening) to coordinate split operation clearly. Critical for organized DX expeditions.
? = Will you listen to… on… kHz?
= I am listening on… kHz
QSX specifies the frequency a station is monitoring — essential in split-frequency DX operation. A rare DX station transmits on one frequency and listens on another to manage the pileup. "QSX UP 5" means listening 5 kHz above its transmit frequency. Every DX chaser needs to know QSX.
? = Shall I send each word or group more than once?
= Send each word or group twice
QSZ improves copy reliability when signals are marginal — by sending each word twice (or more), missed characters can be filled in from the repeated transmission. Used in formal radiogram traffic under difficult conditions. The word count in the preamble covers only the original, not the repeated words.
? = Shall I cancel message number…?
= Cancel message number…
QTA cancels a specific numbered message in a traffic sequence. Used when a message was sent in error, superseded, or no longer valid. The message number (from the preamble) must be specified. Formal traffic nets maintain logs and QTA ensures both stations remove the invalid message from their records.
? = Do you agree with my word count?
= I do not agree with your word count
QTB flags a discrepancy between the word count in the message preamble and the actual words received. Formal radiograms include a word count as a check figure. If the counts don't match, QTB triggers a review — the sender retransmits the message text while the receiver counts each word carefully.
? = Will you send your call sign for tuning purposes?
= I will send my call sign for tuning
QTS requests a station to transmit its callsign continuously so a receiving operator can tune their receiver or antenna for best signal. Before automatic antenna tuners, QTS was standard procedure before a contact. The station sends its callsign repeatedly while the other adjusts for peak signal.
? = Will you keep your station open for further communication?
= I will keep my station open until…
QTX requests or confirms that a station will remain on frequency and operational for continued communication. Used in traffic nets and maritime communication to ensure a relay station stays available. "QTX until 2000Z" means the station will maintain a watch until 20:00 UTC.
? = Have you news of…?
= Here is news of…
QUA requests or provides information about a specific station — its status, location, or latest communication. Used historically in maritime operations when a vessel's position was needed. In modern ham radio, QUA occasionally appears in emergency nets when the status of a specific operator or location is needed.
? = What is the number of the last message you received from me?
= The number of the last message received from you is…
QUC synchronizes message sequence numbers between stations to ensure no messages were missed. If the last confirmed message number doesn't match the sender's records, the gap reveals which messages need to be retransmitted. Critical in high-volume traffic nets where continuity of the message sequence must be verified.
? = Have you received the urgency signal sent by…?
= I have received the urgency signal sent by…
QUD confirms receipt of a maritime urgency signal — one step below distress (SOS). An urgency signal (PAN PAN in voice, or XXX in CW) indicates a serious situation that requires assistance but is not yet life-threatening. QUD ensures all stations in range know the urgency message was received and acknowledged.
? = Can you communicate in… (language)?
= I can communicate in… (language)
QUE addresses language capability in international contacts — one of the original purposes of Q codes as a language-neutral system. Before Q codes, operators struggled to communicate across language barriers. QUE ENGLISH, QUE FRENCH, QUE SPANISH etc. quickly establish a common working language for the contact.
? = Have you received the distress signal sent by…?
= I have received the distress signal sent by…
QUF confirms that a distress signal (SOS or MAYDAY) from a specific vessel or station has been received and acknowledged. All stations receiving a distress signal are required by international convention to acknowledge receipt. QUF creates a formal record of who heard the distress call and ensures rescue coordination can begin.
? = Are you ready for automatic operation?
= I am ready for automatic operation
QRR confirms readiness for automatic or unattended station operation — where a transmitter runs under computer or timer control without a live operator present. Used in beacon stations, WSPR stations, and automated message systems. The receiving operator knows no human is immediately available at the other end.
Type any text including Q codes and hear it in Morse. Try: QTH BOSTON QSL 73.
Hear a random Q code in Morse and type what it is. Trains your ear to recognise the most important operating codes.
Test code → meaning and meaning → code. Start with the 10 essential codes every operator knows before tackling all 57.
Q codes are three-letter abbreviations starting with Q, standardized by the ITU for radio communication. They originated in maritime telegraphy in 1912 to speed communication and overcome language barriers. Each code has a question form and a statement form. All 57 ITU Q codes used in ham radio are listed on this page.
QTH means location or position. As a question, QTH? asks "where is your location?" As a statement, QTH gives your location — city, state, country, or Maidenhead grid square. QTH is one of the most used Q codes in any ham radio contact.
QSL means "I acknowledge receipt" or "confirmed." The QSL card — confirming a contact — takes its name from this code. QSL cards are exchanged as proof of contact for awards like DXCC and WAS.
QRP means reduce power or low-power operation. QRP operators run 5 watts or less. The QRP community is one of the most active in amateur radio, with dedicated clubs, contests, and frequencies. Making contacts across continents on 5 watts is a popular and rewarding challenge.
QRM means man-made interference. It is rated on a scale of 1 to 5 (1=none, 5=extreme). QRM comes from other radio stations, electrical equipment, or digital noise. It differs from QRN which is natural static. "Heavy QRM" on a frequency means significant interference from other transmissions.
QRZ means "who is calling me?" It is used when a station hears a call but cannot identify the caller. QRZ.com, the world's largest callsign database, takes its name from this code. On CW, QRZ? is sent when the callsign was not copied clearly.
QSO means a radio contact — any completed two-way communication between stations. Operators log QSOs with date, time, frequency, mode, and signal reports. "I had a QSO with Japan" means a successful contact was made. A QSO can last from 30 seconds to several hours.
QRM is man-made interference (other stations, electronics, power lines). QRN is natural static (lightning, atmospheric noise, precipitation). Both are rated 1–5. QRN tends to be worse on lower frequencies (160m, 80m) in summer. QRM is common on busy HF bands regardless of season.
QSK means full break-in CW operation. The transmitter switches to receive between every dit and dah, so the other operator can interrupt at any moment. It is the most conversational CW style. "Running QSK" means you can interrupt between the station's own signals.
The ITU standardizes 57 Q codes used in amateur radio and general radio communication, all listed on this page. Additionally there are Q codes specific to aeronautical (QA-series) and maritime services. The amateur radio community also uses informal Q codes not in the ITU list, such as QRO (high power) being expanded beyond its ITU meaning.