A candidate is a question, not a deletion.

Two similar records may describe one QSO copied between loggers, or two legitimate QSOs made close together. QSO Merge Bench offers candidates and keeps both records until you explicitly merge them.

The matching window

Contacts need the same trimmed, case-normalized CALL, BAND, MODE and SUBMODE. They also need valid QSO_DATE and TIME_ON values. The UTC timestamps must fit the selected maximum time difference (0, 30, 60 or 120 seconds), inclusive, even across midnight. HHMM times are treated as second zero for comparison only. Original field values are kept.

For example, W1AW on 20M CW at 14:30:00 and 14:30:30 becomes a near candidate. At the default 120-second window, the same contact at 14:32:01 falls outside. A 0-second window requires equal normalized timestamps. Changing the window clears existing decisions. A 40M contact, different submode or different callsign does not become that pair.

What exact means

An exact candidate has the same complete set of field names, values and optional type indicators. Field order can differ. Values are compared exactly, so a lowercase value or four-digit time can create a field conflict even when the matching key normalizes it. Exact candidates still require an explicit merge decision.

Ambiguous groups

One contact can be close to several records in the other file. All qualifying pairs are shown, up to the 2,000-pair cap. A source contact can participate in only one merged pair. Once merged, overlapping candidates cannot also merge unless you undo the earlier decision with Keep both contacts.

Known omissions

There is no within-file deduplication, frequency-to-band conversion, mode-family translation or tolerance for a shifted clock beyond two minutes. Missing or invalid matching fields leave contacts unmatched and retained. This narrow method avoids automatic guesses but can miss duplicates. Read the support limits and field decision guide.

The ADIF Date and Time definitions inform timestamp parsing. Candidate matching itself is an application policy.