Cabrillo Logs and the UBN Process: Getting Your Contest Score Right

Every contest score eventually gets checked against everyone else’s log, and the format that makes that cross-checking possible is Cabrillo. A clean Cabrillo file gets processed without drama; a messy one can cost you QSO credit, multipliers, or trigger the exact kind of log-checking flags — busted calls, unique contacts, not-in-log entries — that show up in a public UBN report with your callsign attached. Understanding both the format and the checking process turns log submission from a black box into something you can actually control.

What a Cabrillo Log Actually Is

Cabrillo is a plain-text log format built specifically for contest submission. Almost every major HF and VHF contest sponsor accepts it, and almost every contest logging program can export it directly, which is what makes it the closest thing the contesting world has to a universal interchange format. Unlike a general-purpose logging format such as ADIF, Cabrillo is deliberately narrow in scope — it exists to describe one contest’s QSOs in exactly the structure that contest’s scoring software expects, nothing more.

Anatomy of a Cabrillo File

Header fields

The top of a Cabrillo file carries header lines that identify the contest, the callsign used, the category you are claiming (power level, operator class, assisted or unassisted, and similar), your claimed score, and contact details for the log submission. Getting these header fields right matters as much as the QSO lines themselves — an entry claimed in the wrong category, or missing a required header field, can be rejected or rescored by the contest committee regardless of how clean the actual contacts are.

QSO lines

Each contact is logged as a single line with a fixed set of fields in a fixed order: band, mode, date and time, your callsign and exchange, and the other station’s callsign and exchange. The exact exchange fields depend entirely on the contest — a DX contest might expect a signal report and serial number, while a state or section-based contest expects a report plus a location abbreviation. Getting the exchange fields in the right order, in the exact format the contest expects, is one of the most common sources of an otherwise valid contact being flagged during checking.

How Contest Sponsors Score Your Log

After the contest closes, sponsors collect every submitted Cabrillo log and cross-check them against each other. Every contact you claim is, in principle, checked against the other station’s own submitted log for that contact: same band, same approximate time, matching callsign and matching exchange. Contacts that match cleanly are confirmed; contacts that do not match at all, or match only partially, get flagged and typically reduce your final score, sometimes along with a penalty beyond simply losing credit for that one contact, depending on the specific contest’s rules.

What UBN Actually Means

UBN reports are how many major contest sponsors summarise log-checking results, both for individual competitors and, sometimes, in aggregate statistics published after the contest. The three letters stand for three categories of flagged contact:

• Unique (U) — a contact that appears in only one log, with no other submitted log to cross-check it against. This does not automatically mean the contact was invalid; the other station may simply not have submitted a log at all. Sponsors typically treat unique contacts differently from confirmed busts, but a high proportion of uniques in your log is still worth investigating.
• Busted (B) — the callsign or exchange was copied incorrectly. This is the category most directly caused by operator error during the contact itself: mis-copied digits, a wrong section abbreviation, or a callsign typo.
• Not in log (N) — the other station’s submitted log has no record of the contact at all, on that band, at that approximate time. This can indicate a genuine copying error on your side, a timing mismatch, or in some cases a contact that simply did not complete correctly even though both operators believed it had.

Exactly how each category is weighted, and what score penalty applies, differs from contest to contest and sponsor to sponsor, so treat the general categories here as a framework for understanding your own UBN report rather than a universal penalty schedule — always check the specific contest’s published rules and log-checking policy.

Common Cabrillo Formatting Mistakes

• Wrong or missing category headers. Claiming the wrong power category, or leaving a required header blank, can affect how your entry is scored and classified regardless of contact accuracy.
• Exchange fields in the wrong order. Different contests order exchange fields differently; exporting a log built with one contest’s template for a different contest is a reliable source of formatting errors.
• Time zone confusion. Contest logs are almost universally expected in UTC. A log exported with local time instead of UTC will misalign every contact’s timestamp against everyone else’s submissions.
• Duplicate contacts left in the file. Most logging software flags likely duplicates automatically, but a manually edited log can reintroduce them, and duplicate QSOs typically score zero or worse under most contest rules.
• Submitting the wrong file entirely. Especially in software that keeps several contest logs open at once, submitting an export from the wrong contest or the wrong session is a surprisingly common, entirely avoidable mistake.
• Inconsistent callsign case or special characters. Portable and special-event style callsigns with suffixes or unusual characters can be mangled by an export process that was not configured for that contest’s specific naming conventions, so it is worth checking those entries in the raw file before submitting.

How to Reduce Busted Calls and NILs Before You Ever Submit

Most log-checking flags trace back to habits during the contact itself, not to anything that happens afterward in software. A few practices make a measurable difference:

• Confirm the callsign before moving on, especially in a fast run where partial calls and background noise make mis-copies easy. A quick, unambiguous confirmation costs a couple of seconds and prevents a bust that would otherwise cost the contact entirely.
• Use your logging software’s built-in checking features — most contest loggers cross-reference incoming calls against a master callsign database and flag likely typos before you log the contact, not after.
• Double-check exchange copying on marginal signals. A weak or fading signal is exactly when exchange digits get mis-copied, and it is worth asking for a repeat rather than guessing.
• Review your log before submission, not just for duplicates but for exchanges that look inconsistent with a station’s known location or category, which can be a sign of a copying error worth double-checking against the actual recording if you keep one.

Software That Generates Cabrillo for You

Every mainstream contest logging program exports Cabrillo directly once you select the correct contest template, which is why getting the contest and category settings right at the start of the contest, not just at export time, matters so much — the export step itself rarely introduces errors if the underlying log and settings were correct throughout.

Submitting Your Log

Most contest sponsors accept Cabrillo submission through a web upload form, sometimes with automatic validation that catches obvious formatting problems before final submission. Take advantage of any validation step offered — catching a header or formatting error before the submission deadline is far better than discovering it in a published UBN report after the fact. Always keep a local copy of exactly what you submitted, in case a question comes up later about your entry, and note the confirmation you receive — a missing confirmation email or upload receipt is worth following up on well before the log deadline rather than assuming the submission went through silently.

Dupe Checking Is Not the Same as Log Checking

It is easy to conflate two things that happen at very different times. During the contest, your logging software’s dupe checker warns you in real time if you are about to log a contact you have already worked on that band and mode — this is entirely about your own log, checked against itself, and it prevents wasted time on a QSO that will not score. Log checking, the process behind a UBN report, happens after the contest closes and compares your log against everyone else’s submitted logs. A log with zero internal duplicates can still generate plenty of busted or not-in-log flags during post-contest checking, because dupe checking and cross-log verification are solving completely different problems.

Why Public UBN Reports Matter Beyond the Score Itself

Some contest sponsors publish detailed log-checking statistics alongside the results, sometimes down to individual callsign level for the categories and error types found. Beyond the direct effect on your score, this visibility is part of why experienced contesters take copying accuracy seriously as a matter of on-air reputation, not just points — a log with an unusually high busted-call rate, published openly, reflects on operating discipline in a way that a private, ungraded log never would. This is also one of the more effective incentives the contesting community has for maintaining good copying habits across the board, since everyone’s numbers are, at least in the aggregate, visible to everyone else.

UBN Categories at a Glance

Frequently Asked Questions

Do all contests use Cabrillo, or are there other accepted formats?

Cabrillo is the dominant format for major HF and VHF contests, but always check the specific contest’s submission page, since some smaller or regional contests may accept other formats or have additional requirements.

What happens if I submit my log late?

Policies vary by contest sponsor, ranging from an outright rejection to a score penalty or a note in the results; check the specific contest’s deadline and late-log policy rather than assuming a grace period exists.

Can I resubmit a Cabrillo log if I find an error after submitting?

Many contest sponsors accept a corrected resubmission before the log deadline; check the specific contest’s rules, since policies on resubmission after the deadline vary and are not guaranteed.

Does a high number of unique contacts always mean I made mistakes?

Not necessarily — a unique contact often just means the other station did not submit a log at all, which happens constantly, especially with casual or non-contest-focused stations working a running station.

Do QRP or low-power entries get checked the same way as high-power entries?

Yes, log checking is generally applied consistently across categories; category only affects how your score is compared against other entries in your category, not whether your log gets cross-checked.

Is it worth keeping an audio recording of my contest operating?

Many serious contesters do, specifically so that a disputed busted-call flag can be checked against what was actually sent and received, rather than relying on memory after the fact.

The Bottom Line

A clean Cabrillo file is mostly a reflection of clean operating during the contest itself — accurate copying, correct exchange format, and careful attention to category and header details matter more than any post-contest editing trick. Understand what U, B and N actually flag, fix the habits that cause them, and use your software’s built-in validation before you submit. For the authoritative field-by-field specification, see the ARRL’s Cabrillo format documentation, and for a real-world example of how log checking and UBN reporting work at scale, the CQ WW contest publishes detailed log-checking results every year.

If you have not settled on contest logging software yet, start with choosing a contest logger: N1MM+, Log4OM and DXLab compared, since accurate Cabrillo export starts with correctly configured logging software. And since operating discipline is what actually prevents busted calls in the first place, run or search and pounce: where contest rate really comes from covers the pacing decisions that affect copying accuracy under pressure.