Can you monitor a VarAC QSO between other stations? Sure you can!

A VARA modem can operate in either Ready-To-Connect mode or Listening (Monitoring) mode.

If you want to remain available for incoming connections while also monitoring the frequency for ongoing VARA activity (such as active VARA QSOs), you will need to run a separate VARA modem instance in Monitor mode.

Open the VarAC Settings, go to the VARA tab, and under VARA Monitor Path, click the small (?) icon for more information.

Monitoring Accuracy

Some operators say they can’t accurately monitor ongoing VARA traffic. Let’s take a moment to understand why that happens.

VARA is an ARQ mode, which means you either receive the data 100% accurately (thanks to CRC error correction) or you don’t receive it at all. In that sense, it is very similar to Pactor or Packet.

When two stations have a strong, stable link (for example around +2 dB SNR) and switch to High Speed mode (for example Level 5), the connection works perfectly between them.

However, if you receive that same transmission at –10 dB SNR, you will likely fail to decode most of it. Too many bytes are lost in the noise, and the CRC cannot reconstruct the packet.

It is similar to trying to copy a high-speed Packet radio signal. It may sound strong to your ear, but the signal-to-noise ratio may still be too low for your modem to decode the data correctly.

In non-ARQ modes such as RTTY or PSK, missing a few characters still allows you to understand the message. With ARQ, every byte in a packet must be received (within certain limits) in order to reconstruct the message. If even a few bytes are missing, the entire packet is discarded.

As a result, you will usually decode more packets at lower VARA speeds than at higher speeds. Just because you can hear a signal clearly does not mean your modem can successfully decode the data.

Here is a real example from my monitor screen on the Calling Frequency. You can spot several interesting elements in it.

Gibberish Text

Some VarAC packets are not part of a live QSO but rather asynchronous VarAC traffic such as Broadcasts, Beacons, and CQ calls. These packets may appear as gibberish on the VARA monitor screen because the monitoring capability can only properly decode live links.

However, these asynchronous packets are already decoded by VarAC and displayed on the VarAC dashboard.

Bottom line

The VARA monitor may show gibberish that actually represents messages VarAC has already decoded and displayed on the dashboard, or it may show clear text from live QSOs that VarAC cannot display directly.