Contest Dupes: How to Handle Duplicate QSOs Properly

Every contest operator knows the sound of it: a station calls on top of a pileup, the callsign is clear, and your logger turns red. You have already worked this station on this band. In contest language the caller is a dupe, short for duplicate, and what you do next affects your rate, your score and the mood on the frequency. Handling contest dupes well is a quiet skill that separates relaxed, efficient operators from those who waste minutes in arguments about who worked whom. This guide explains what counts as a dupe, how loggers check for them, what dupes cost, when it is wise to work one on purpose and the polite words to use on the air.

What Is a Duplicate Contact

In a contest, a station may normally be worked once for credit on each band, or once on each band and mode if the contest allows several modes. A second contact with the same station under the same conditions is a duplicate. It earns no additional points, and it does not add a new multiplier. In most contests the duplicate is not penalised, and the operator simply loses the time it took, but the rules of each event define the details, and a few contests do remove or penalise some extra contacts. Always read the section on duplicates in the rules, as the principle that a contact counts once per band is only the most common arrangement. For general background see the overview of amateur radio contesting and our article on contest categories.

The definition of the band and mode matters. A contact on 20 metres CW and another on 20 metres SSB are two valid contacts in a mixed-mode event, but they are the same in a CW-only contest, where the mode is not a variable. In an event where each band counts separately, a station that you worked on 40 metres is a new contact on 80 metres, and in some contests a repeated contact is allowed after a specified time. Digital and phone events often add more rules, so the best protection is a look at the rules a few days before the start.

How a Logger Finds Dupes

Modern contest loggers check for duplicates automatically while you type. As soon as you enter the callsign, the program compares it with the contacts already in the log for the current band and mode and displays a warning if it finds a match, often by colouring the entry field or by showing the earlier contact. The setup guide for N1MM Logger+ shows the options, and the overview in the article on choosing a contest logger compares the programs.

Two features help. The first is the check window that shows partial matches and previous contacts as you type, so you know before the full callsign whether the station is already in the log. The second is the use of the call history and master files, described in the article on Super Check Partial, which complete the callsign and fill in the exchange. Both help the operator to confirm a callsign sooner, and the earlier the dupe is known, the less time it wastes. In a run, the dupe check happens after the first copy of the callsign, which is why a good operator keeps the first fragment of a call in view and does not send the report before the check has finished.

What Dupes Really Cost

The direct cost of a dupe is the time spent on the exchange. At a rate of 60 contacts an hour, each contact takes about a minute, so every dupe costs one contact. In a 48-hour contest with a hundred dupes, that is nearly two hours of operating, and more if the rate is high. The indirect cost is the rate itself: a dupe interrupts the rhythm of calling and listening and invites other callers to hold back. The article on running and search and pounce explains how rate is built, and dupes damage it from both sides.

There is also a reputation cost. A station that repeatedly calls the same CQ caller gets a reputation as careless. A station that calls a wanted station again and again in the hope of a second multiplier is wasting everyone’s time. A little discipline in this respect is part of contest etiquette.

Dupes From the Running Side

When you are running, with a frequency of your own, you decide how to deal with a dupe. The options are to work it, to tell the caller, or to ignore it. Working it costs a few seconds, yet it keeps the pileup moving and is the polite choice at a low rate. Telling the caller keeps the log clean: a short phrase such as “dupe, thank you” at the end of your exchange, or sending “QSO B4” in CW, lets them know that they are already in your log and that they can go on. At a very high rate, many operators prefer to log the second contact too without comment, since two seconds of a repeated exchange cost less than the explanation. It is a matter of judgement, and the level of the rate decides it.

Never be rude. The caller may be sure that you did not log them, and in a way they could be right: it is possible that the earlier contact was a busted call. If they insist, give them the exchange again. The penalty for a bad contact in the log, described in the article on Cabrillo logs and the UBN process, is usually greater than the time cost of one more contact.

When to Work a Dupe on Purpose

There are good reasons to work a dupe. The first is doubt: if you are not sure that your earlier contact with a station was complete and logged with the right exchange, a second contact removes the risk of a not-in-log penalty on their side or on yours. A contact that is wrong in either log might be removed, with an additional penalty in some contests. A second contact costs you about a minute of time, and a failed first contact can cost points and, in the case of a multiplier, a lot more.

The second reason is the multiplier: if a station was worked earlier on the wrong band or the wrong mode in a log that is not corrected, or its exchange was incomplete, the new contact can fix it. The third reason is a change of rules, for example when the contest allows a repeat after a number of hours. The fourth reason is mundane: the caller is a friend or a club member and you simply want to say hello. In all these cases, tell your logger that you are doing it knowingly, by using the key combination that logs a dupe or by marking the contact, so that the duplicate is not scored as a real contact. Most programs mark such contacts so that they do not count and so that your Cabrillo file is correct.

Dupes From the Pounce Side

When you are tuning the band and calling stations, the logger should be open and the callsign entered before you call. Type the callsign as soon as you decode it and check the colour before you press the call key. A dupe on this side is entirely your fault, and it wastes the other station’s time too. If you are using a skimmer or the call-history tools, they can display a station as worked, which colours the spot in the band map and makes it easy to skip. The practice of checking before calling is one of the basic habits of efficient search and pounce.

A related habit is to log carefully. A contact entered twice by accident is a duplicate that appears in your own log. Check that Enter has not been pressed twice, especially with a keyboard shortcut for logging, and scan the log from time to time, as you can in the dupe sheet view. Programs have a function to show the log sorted by callsign, so repeated entries stand out.

Special Cases: Multi-Operator Stations and Changing Callsigns

Some situations make dupe checking harder. At a multi-operator station, several people and several radios share one log over a network, and a contact made by one operator must appear at once at the others, or two radios will call the same station within minutes. The network setup and the rules of the categories are described in the article on multi-operator contesting. A delay of a few seconds in the network is acceptable, but a broken link is not, and a team should check the connection at the start and again every few hours.

Callsigns can also change within a contest. A station may sign with a portable suffix, a special event call, or a different call on another band, and the rules decide whether these count as the same station. In most contests the full callsign, including the suffix, defines the station, so a contact with a call and the same call with a suffix are two different contacts for the log, even though the person is the same. A few events treat the base call as the identity. The logger follows the option you have set, so confirm it before the start.

Mode changes need the same care in mixed-mode events. When the other station answers in a different mode, such as CW after your SSB call, your logger must switch to that mode, or the contact is stored against the wrong mode and the dupe check fails. Keep the mode field in sync with the radio, using the CAT control, and look at it whenever you change.

Paper Dupe Sheets and Reviewing the Log

Before computers, dupe checking was done on paper, with one sheet for each band, with the callsigns written in sections by the first letter or number. The principle still works as a backup. In a small event or a field station without a computer, a paper dupe sheet is simple and reliable. After the contest, the log checking robots find all the duplicates in your submitted log, and you can review them yourself first with the tools in the article on contest log analysis. If the number of dupes is much higher than 2 or 3 percent, you probably lost rate and can improve your technique.

The Bottom Line

A contest dupe is a repeated contact with the same station on the same band, or band and mode, which earns nothing and usually costs only time. Loggers flag dupes as you type, so check before you call, and when you are running tell callers politely that they are already logged or just work them at a high rate. Work a dupe on purpose when you doubt the first contact, and mark it in the logger so it does not count. Read the rules for the exact definition, keep the log clean and keep your rate high.

Frequently Asked Questions

What is a dupe in a contest?

A duplicate contact: a second QSO with a station you have already worked on the same band, or on the same band and mode, in the same contest.

Do dupes lose points?

In most contests a dupe earns no points and is not penalised, but you lose the time. A few contests have special rules, so read the section on duplicates.

Should I work a station that calls me twice?

If you are sure you have logged them, tell them politely or work them quickly at a high rate. If you are unsure, work them again, because a missing contact costs more.

How does a logger detect dupes?

It compares the callsign you type with the log for the current band and mode and flags a match, often by colour, before you finish the exchange.

What does QSO B4 mean in CW?

It means the contact was made before, so the caller is already in your log.

Can I log a dupe so that it does not count?

Yes. Most contest loggers allow you to mark a contact as a dupe, so it stays in the log but is not scored or submitted as a valid contact.