This application note attempts to describe the difference between Filters, Groups and Selections, and the situations for which they are most appropriate.
From the DX4WIN Help File:
IMPORTANT: When DX4WIN is started (at least versions 8.05 and earlier), all filters and selections are CLEARED; DX4WIN starts in the "All QSOs" group (#0). This means that all the QSOs in your logbook are visible. There is no way to start DX4WIN with a given Selection or Filter set; that can only be done after you have started the program.
A filter allows you to navigate through your log, seeing only the QSOs that match the filter (for example, find all your confirmed QSOs with Corsica, TK). You can search on any combination of fields in your logbook; a QSO has to match all of the fields whose values you specify in order to be found using the filter.
There are two ways to activate a filter:
When a filter is active, you can use the Page Up/Down keys to move amongst the QSOs in the filter. You will also see "Filter Active" in the main DX4WIN menu:
When you perform certain operations, such as printing QSL labels or exporting QSOs, DX4WIN may ask you if you want to use the filter that is currently active. Answer YES if you want to perform that operation using only the QSOs that match the current active filter, or NO if you want to perform that operation on all QSOs in your log.
Filters have no effect on Windows and Reports. For example, if you use F8 to filter your log for only CW QSOs, and you have the Country window open, you'll still see W/L/M/C (worked/label/mailed/confirmed) status in the Country window for all other modes.
To clear the currently active filter, use the ESCape key.
Groups are a way to tag certain QSOs as being "together". Group numbers range from 1 through 65533. Group #0 is the "all QSOs" group. Group numbers 65534 and 65535 are used internally and should not be assigned to any QSO.
A QSO can only be assigned a single group number (i.e. can only be in one group). However, you can create a Selection which includes multiple groups (see the Selections section below).
There are two parts to a group: the group number and the group name. The group name (if a group number is assigned to the QSO) is visible in the rightmost column of the Same Call window:
There are three ways to assign a group number:
To create a group name from the QSO window, choose Filter | Edit Group Names. Type a name for the group into the single-line entry box (just above the buttons), and they click on the Add button. Note that group names must be assigned sequentially (in numerical order, starting with group #0), so it's best to create the group name FIRST, before assigning group numbers to QSOs (the number for a group is assigned when the group name is added). To skip a group number, click on the Add button without typing a group name. You can create as many group names as you want (up to the program limit), even if you will not use them immediately. It's best not to assign a name to the "All QSOs" group (group 0).
Group names can be printed on QSL labels.
Selections are similar to filters, but have one important difference. When you make a Selection, not only is your visible logbook "narrowed down" to only the QSOs that are in the selection, but all windows and reports will use only QSOs from the current selection. Other operations such as marking QSOs (setting multiple label flags) and multiple QSO operations also operate only on QSOs in the current selection.
The name of the selection is shown in the banner of the QSO window:
Within a selection, you can use F8 to filter QSOs even further; filtered QSOs are only chosen from within the current selection.
When you save your logbook to disk, all QSOs are written - both those in the current selection as well as those which are not currently visible.
There are three different kinds of selections:
The QRP and YLop selection filters will select only those QSOs from your logbook that have the QRP and/or YLop fields set to 'Y'. These two filters can be part of a Group or Date filter (i.e. all YL QSOs made from 2000-2009), or can stand alone (i.e. a selection for only QRP QSOs).
A Date selection may have only a starting date, only an ending date, or both starting and ending dates (a range of dates). You can create different selections that have overlapping date ranges, but only one selection can be active at a time. Date selections are a good way to delineate your logbook by the callsigns you have used, assuming the dates you used those calls don't overlap. This leaves group numbers available for other uses.
A Group selection may have one or more group numbers selected. For example, if you have a different group number for each CQ WW contest you logged, you could create a selection that includes all of those contest QSOs in a single selection:
To clear a selection, from the QSO Window go to Filter | Selection and use the drop-down box at the top of the window to select a different selection, or All QSOs.