Syllabus Sections:-

Receiver Concepts

3H3   25  Understand that overloading a receiver causes intermodulation products and that those close to or within the wanted signal bandwidth limit the ability of the Receiver to detect weak signal

Firstly what is Overloading a receiver ?? A receiver's input becomes overloaded when it receives very strong signals, usually from a nearby transmitter. Notice the use of the word "Signals" not a single signal but multiple signals, when two or more strong signals enter the receiver “Intermodulation” occurs and the products are the sum and difference of those signals.
When those signals are close to, or within the bandwidth of the wanted signal, the receiver will find it very hard to detect the wanted weak signal. The ability to detect weak signals is called "Sensitivity".
So if you were to build a receiver you would need to consider in your designs the quality of components, to limit the amount of internal noise from those components and use the minimum amount of bandwidth within the receiver which would then minimise external noise picked up by your receiver..

Recall that the dynamic range of a receiver is the difference between the minimum discernible signal and the maximum signal without overload.

“Dynamic Range”, see Fig 9.2 page 58 for diagram in the RSGB Full licence manual, is a term used to describe the difference between the quietest signal or “minimum discernible signal”  and the loudest or “maximum signal of  un-distorted sound” or a “signal  without overload”.
There will be some signals that you receiver will just not be able to hear because they are below the noise floor level of the receiver and those that are so strong that they overload the receiver. This is much like you can hear a conversation from across the room - until someone next to you starts shouting which overloads your ears and cuts out the weaker signal.

Recall the dynamic range is expressed in decibels.

The "dynamic range"  is expressed in decibels dB.

Dynamic range is the difference between the receiver’s sensitivity (from the weakest signal it can detect) and to the point where overloading is about to occur in the receiver.

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