Log4OM 2 Setup Guide: Logging, CAT Control and DX Cluster

Log4OM is one of the most widely used general-purpose logging programs in amateur radio, and version 2 is free. It does far more than record contacts: it looks up callsigns, tracks awards, shows cluster spots on band maps, predicts propagation, talks to your radio and exchanges data with digital mode programs. That breadth is also why a first Log4OM setup can feel overwhelming. There are many settings, and most of them can wait.

This guide walks through a practical setup for a typical home HF station, in the order that makes sense: installation, station details, callsign lookup, CAT control, the DX cluster, integration with WSJT-X and similar programs, QSL services and, finally, backups. Feature descriptions follow the official Log4OM website and its release notes. For exact menu wording in your version, keep the official Quick Start Guide open next to you.

What Log4OM 2 Is and What It Needs

According to the Log4OM download page, Log4OM is free, written in C#, and runs on Microsoft Windows starting from Windows 7, with .NET Framework 4.7.2 required. Current releases are 64-bit only. Each release is offered as a normal installer and as a portable version, and the download page lists a SHA-256 checksum for every file so you can verify what you downloaded.

The project releases updates regularly. At the time of writing, the stable release listed on the download page is 2.42.1.0, published on 24 September 2026, and the release notes describe changes ranging from CAT engine fixes to new notification features. Version numbers move quickly, so always take the current one from the official page rather than from an article.

Log4OM’s main support channel is its user forum, and the resources page links to a Quick Start Guide, a Basic User Manual and an Advanced User Manual in English, plus translations in several other languages.

If you are still deciding between loggers, our comparison of N1MM+, Log4OM and DXLab explains where each one fits. In short, Log4OM is a strong choice as a general station log; dedicated contest loggers still have an edge during a major contest.

Step 1: Install and Create Your Logbook

Download the installer (or the portable version if you want to run it from a folder or USB drive), check the SHA-256 value if you like, and install it. On first start, Log4OM asks for basic information and creates a logbook database for you.

A few decisions are worth making now rather than later:

• One logbook per callsign. If you hold more than one callsign, or operate a club station, separate logbooks keep award tracking and QSL uploads clean.
• Where the database lives. Most single-operator stations simply keep the local database on the shack PC. Log4OM also supports MySQL and MariaDB, and the 2.42.1.0 release notes mention connection pooling for those databases, which is useful for shared or remote setups.
• Importing an old log. If you are moving from another program, export your log as ADIF and import it into Log4OM. Our guide to moving your log between programs with ADIF explains how to check that nothing is lost on the way.

After an import, take a few minutes to compare the QSO count and a handful of random contacts against the old program. It is much easier to fix a mapping problem on day one than after months of new contacts.

Step 2: Station Information and Callsign Lookup

Next, enter your station details: callsign, name, locator, and the location information your QSL services and awards need. Accurate station data matters because Log4OM uses it for distance and bearing calculations, propagation predictions and award tracking.

Then configure callsign lookup. The official feature list says Log4OM can look up calls through several external sources, including QRZ.com, HamQTH, QRZCQ and HamCall, as well as an internal Club Log based database, with automatic fallback to a secondary source when the primary one returns no data. Practical advice:

• Choose the service you already have an account with as the primary source.
• Add at least one fallback, so lookups keep working when one service is slow or returns nothing.
• Let Log4OM keep its country files updated. The site notes that it uses an internal and constantly updated Club Log database and CTY file for zone and callsign exceptions.

Log4OM also works without an internet connection when necessary. According to the official “Connected” page, its resources are updated and stored locally, so a portable station can log normally offline and later bulk-update the new QSOs with online lookups once the laptop is back home.

Step 3: CAT Control

CAT control is what turns Log4OM from a manual logbook into part of your station. With CAT active, the program reads your frequency and mode, fills them into each QSO automatically, and can tune the radio when you click a cluster spot.

Choosing a CAT engine

Log4OM offers several ways to talk to the radio. The release notes mention Hamlib and OmniRig connection checks, a TCI CAT engine for radios that support that protocol, and, since version 2.41.0.0, support for CAT4OM, a separate Computer Aided Transceiver program, including CW keying through CAT4OM. Newer features such as an SWR bar under the active frequency and an audio recording button are listed as requiring the CAT4OM engine and a radio that supports them.

Whichever engine you pick, the basic rules are the same as in any rig control setup: select the correct radio model, set the COM port or network address, match the baud rate and handshake settings to the radio’s menu, and confirm that only one program owns the serial port at a time. If two programs need the radio at once, use a shared engine or a port-sharing tool rather than fighting over the port. Our article on rig control with Hamlib covers these basics in more depth, and the Hamlib project site lists supported radios.

Checking that CAT really works

Once connected, change frequency and mode on the radio and confirm that Log4OM follows. Then click a frequency in Log4OM and confirm that the radio follows. The 2.41.0.0 release notes describe additional checks for Hamlib and OmniRig that verify the radio is effectively connected before showing CAT status as active, and version 2.42.0.0 added an on-screen notification centre that explains failures such as a rejected connection instead of only writing them to a log file. If something is wrong, that notification is the first place to look.

Step 4: DX Cluster and Band Maps

Log4OM can connect to DX clusters and show spots in its cluster window and on band maps. The feature list describes multiple band viewers, each filtered by mode and band, and the 2.42.0.0 release notes mention improved cluster performance under heavy load from skimmer spots.

A practical cluster setup looks like this:

1. Add one or two reliable cluster nodes. Start with a node close to you geographically and keep a second one as a backup.
2. Filter early. Show only the bands and modes you actually operate, otherwise skimmer traffic will bury the spots you care about.
3. Use the worked and confirmed status colours, so new entities, new band slots and needed awards stand out at a glance.
4. Click a spot to tune the radio through CAT, then check the callsign before you call.

Spots are only as good as the people and skimmers posting them. Our guide to DX cluster spotting, etiquette and filtering explains how to cut the noise without missing the rare ones.

Log4OM also integrates VOACAP propagation prediction with callsign lookup and the cluster. The official site describes it as predicting the probability of a contact, and the 2.41.0.0 release notes mention roughly four times faster VOACAP calculations in some cases. Treat it as a guide to which band is worth trying, not a guarantee.

Step 5: Connecting WSJT-X, JTDX and Other Programs

Many operators use Log4OM as the central log while FT8 runs in WSJT-X or JTDX. Log4OM’s integration engine is built on UDP. According to the “Integrated” page, Log4OM works with JTAlert, PSTRotator, Fldigi, JTDX, WSJT-X, N1MM and QARTest, and it can accept an unlimited number of inbound UDP connections for ADIF, JTDX/WSJT-X, N1MM and QARTest messages, on as many ports as you need.

A typical WSJT-X link

• In WSJT-X, enable logged QSO broadcasting to a UDP address and port.
• In Log4OM, add an inbound UDP connection on the same port, of the matching type.
• Make a test QSO, log it in WSJT-X, and confirm it appears in Log4OM with the correct band, mode and time.

If two programs need to read the same UDP messages, only one can normally receive them. Log4OM includes a UDP proxy that receives a message, uses it, and rebroadcasts it on a different port so other applications can use it too. The 2.42.0.0 release notes also describe fixes in this area: outbound UDP connections are now stored with the correct target address and port, and the connections panel refuses settings that would send messages back into Log4OM itself and create an endless loop. If you upgraded from an older version and an outbound UDP connection stopped working, check that panel first.

Multi-operator and remote use

The same engine supports more ambitious setups. The official site gives the example of receiving UDP ADIF messages from ten different ports into one Log4OM instance, combining QSOs from several operators into a single logbook. Log4OM can also monitor ADIF files for changes, forward logged QSOs to other services and be remote-controlled from another application over UDP.

Step 6: QSL Services and Awards

Log4OM is fully integrated with the major online confirmation services. The feature list names LoTW, eQSL, QRZ.com, HamCall, Club Log, HamQTH and HRDlog.net. For most DXers the priorities are:

• Logbook of The World. Set up your certificate and station location in the ARRL software first, following the ARRL LoTW pages, then point Log4OM to it for uploads and confirmation downloads.
• Club Log. Automatic uploads keep your DXCC tables current and help DXpeditions match QSOs.
• eQSL and QRZ.com. Useful for awards and for stations that do not use LoTW.

The award engine is one of Log4OM’s strengths. The official site describes more than 40 preconfigured awards, full SOTA and IOTA support, and three types of user-defined award: driven by a QSO field, by callsign, or by a reference such as a park or summit. Awards are centrally maintained by the Log4OM team, SOTA and IOTA lists update from their own sources, and since 2.41.0.0 user-made awards are restored automatically when a new release starts for the first time.

Configure the awards you actually chase first, then download confirmations and let Log4OM recalculate. Seeing your real worked and confirmed totals is the best motivation to keep the log tidy.

Step 7: Backups You Never Have to Think About

A log is years of operating history, and losing it hurts. Log4OM’s “Safe” page describes a sensible default: a full ADIF backup on each program shutdown, at least six backups kept for a minimum of six different days, and the last backup of each month stored permanently. A secondary backup location with unlimited backups can also be configured, and the site suggests placing it in cloud storage or on a different disk.

Set that secondary location on day one. A backup on the same drive as the database does not protect you from a failed disk. Together with regular uploads to online services, it gives you three independent copies of your log with no daily effort.

Common Setup Problems and Quick Fixes

• CAT shows connected but frequency does not update. Check the radio model, baud rate and that no other program holds the COM port. Read the notification centre message, which in recent versions links to the relevant settings page.
• WSJT-X QSOs do not arrive. Compare port numbers on both sides, confirm the connection type, and make sure two programs are not both listening on the same port without the proxy.
• Wrong country or zone for a callsign. Update the country files and check the callsign exceptions before editing QSOs by hand.
• Award totals look too low after import. Download confirmations from LoTW and other services, then let the award engine recalculate.
• After an upgrade, a feature behaves differently. Read the release notes for that version; they list changes and fixes in detail.

The Bottom Line

A good Log4OM setup is built in layers. Install the current 64-bit release, create a clean logbook and import your old log via ADIF. Enter accurate station data and configure callsign lookup with a fallback. Pick a CAT engine that suits your radio and confirm it works in both directions. Add a filtered DX cluster, connect WSJT-X or JTDX over UDP, and set up LoTW and Club Log uploads. Finally, point the secondary backup to a different disk or cloud folder. Do these steps once, carefully, and Log4OM becomes the quiet centre of your station rather than another program to babysit.

Frequently Asked Questions

Is Log4OM free?

Yes. The official download page states that Log4OM is free. It runs on Microsoft Windows from Windows 7 onward and requires .NET Framework 4.7.2; current releases are 64-bit only.

Which CAT engine should I use in Log4OM?

Use the one that supports your radio best and fits the other programs on your PC. Log4OM works with Hamlib, OmniRig, TCI and, since version 2.41.0.0, CAT4OM, which is required for some newer features.

How do I log FT8 QSOs from WSJT-X into Log4OM?

Enable logged QSO broadcasting over UDP in WSJT-X and add a matching inbound UDP connection on the same port in Log4OM. Make a test QSO and confirm it arrives with the correct data.

Can I use Log4OM without an internet connection?

Yes. Log4OM keeps its resources locally, so you can log offline, for example when operating portable, and update the new QSOs with online lookups later.

Does Log4OM back up my log automatically?

Yes. It makes a full ADIF backup on each shutdown, keeps at least six daily backups and the last backup of each month, and can store unlimited backups in a secondary location such as a cloud folder.

Can Log4OM upload to LoTW and Club Log?

Yes. Log4OM integrates with LoTW, eQSL, QRZ.com, Club Log, HamQTH, HamCall and HRDlog.net for uploads and confirmations. LoTW requires your ARRL certificate to be set up first.