Core radio communications concepts

Last Updated on October 26, 2023 by John Berry

There’s a lot to amateur radio. It’s not essential that radio amateurs understand all the core radio communications concepts – but it helps!


When one radio amateur sends a signal to another, there’s a chance that the signal will be received above the threshold of reception. If the signal received is indeed above the threshold of reception, an exchange of voice or data messages may be possible. Chance governs communication between amateur stations. Many amateurs embrace this, and chance gives the well-established concept of ‘DX’. Read why chance is so significant to radio amateurs.

System Value

The system value is the maximum loss between the transmitter output and the receiver input for a given response in the receiver. The system value is a fixed value for that system technology (comprising modulation and coding). There are differing system values for narrow band FM voice, SSB and each narrow band data mode such as FT8. Here’s how it’s calculated.

Path Budget

A path budget is as it implies – a currency pot in decibels that you as radio amateur can ‘spend’ in communicating with others. It’s not quoted in monetary terms – though some might argue that the bigger your purse, the greater the path budget and resulting DX. But that’s another story. The path budget guides the way you choose to spend your system value, and the benefit you get as a result of choices you make. Here’s how it’s calculated.

Receiver threshold

The threshold of reception is.. well, just that. It’s the input to a receiver required to just produce the required communication result. The receiver threshold forms one of the two parameters to calculate the System Value. The other is the power output from the corresponding transmitter. The System Value is the total loss permissible between transmitter output and receiver input. Click for more on receiver threshold.

System noise

Radio amateurs are interested in the signal to noise ratio of received signals. To include electrical noise (from the various system components including antenna array, low noise amplifier and feeder) we need to be able to calculate the threshold degradation. This is explained here using a cascade approach to reveal the system noise figure and deduce how the sensitivity changes.

Data modes

DX – the seeking out of rare amateur stations at vast distance – is a central focus of many radio amateurs. Modern data modes materially affect the hobby by making rare not so rare, and shrinking distance. The outcome of such a revolution has been questioned by many in the hobby. They wonder “whither amateur radio”. If it all becomes too easy – like shooting fish in a barrel – where’s the fun. Watch the video here and add to the debate.