Interesting....
Quite the question!
When you ask this question -
Squelch and RF gain, I keep reading how they’re not the same but then the explanations go on to describe them both seeming to do the same thing. I understand squelch restricting sensitivity to keep noise and weak signals out, but then it seems RF gain also works so that only stronger signals can get through.
As you already experienced, Squelch does not change
"Sensitivity" nor does it do anything for
"Selectivity" - two factors that Squelch ignores, but RF Gain can utilize.
Ok, grab your owners manual - look up the "Specifications" section...
Perhaps you'll need to look at how the radio is rated as a performer - not just that it has the ability to receive signals and you hear them.
I'm sure you've heard the "bleedover" or worse, a type of condition where the radio itself - sensing a strong signal on another channel - tends to reduce the ability to even hear the signal on the channel you are trying to listen on. A factor called
(Image) Rejection or
Adjacent Channel Rejection - these two add into a figure of merit that looks at the radios' ability to "hear" the channel you selected - not everything else.
So really, any radio can operate like any other - if you only used the Squelch control and volume - but the reasons for RF Gain and the others like ANL and NB - provide a level of filtering and performance to aid you in finding and keeping a QSO working when other operators or ambient noises are creating conditions that make that very effort extremely difficult.
To help you start down the right paths of using your radios' features, you can think of RF gain as a means to knock down the overall level of noise and signal you have to process your antenna has sent to your radio. The receiver works with less input signal affecting all the range of frequency including on the channel. A factor of Selectivity and Sensitivity - letting the radio do the work of finding and pulling out the signals you want to hear.
ANL is better for taming noise you have within the signal and the channel you're QSO-ing on. NB is even better for the MODE of operation you're in.
Did you catch that? MODE - being SSB, FM or AM or even CW - no matter the mode, the RF Gain helps in knocking down the overall input receiver signals and noise strength by reducing the receivers Sensitivity - letting the radios - Selectivity take over and provide some better control over the bandwidth of noise still present - with the desired result being the noise is less around the frequency or channel you are working. .
You cannot remove the noise present within the signal - that requires processing - so much of the ANL NB debate is mostly to focus on the Amplitude of the noise compared to the waveform of the audio signal - that is a form of processing - clipping - and blanking - both are a form of processing - designed to lessen - even remove - noises that do not "match" a pre-determined slope rise or fall - that can be called audio - so filters are also a part of this as a form of smoothing during the processing.
Since AM was a common method of transmission (still is) the effort to reduce noise was to attempt to limit, clip or blank out - sections of audio signal so you didn't have to listen to the noise - just the audio present in the signal.
But SSB, can't utilize ANL like AM can, so by signal containing both the strength in carrier and audio in envelope - ANL uses the signal strength and compares or processes the Audio in the envelope - using the signals strength to clean up noise and let more audio be heard as the signal receiver gets stronger. Then ANL stops working so it doesn't over process the signal - by the factor of compensation. Once it gets a signal strong enough - it doesn't smooth out any more audio - it simply rides along thru the filtering network unprocessed but still filtered.
Noise Blanker is similar - but resides as part of the radios own IF processing section - so it too sees a sample of the input the receiver sees and then tries to sample, develop a signal from the impulse noises present in the sample - to obtain a working pulse - and inverts the pulse and use it to send signal that would have the impulse noise - sent to ground or some of the signal - sent to ground - so the rest can then be processed and detected. What you hear is lesser noise and impulses that otherwise mask the audio.
The RF Gain control is often a mis-diagnosed cure for a situation of others that wish to use the radio in and around other radios with strong signals that use different channels - only to find that the RF Gain is useless to reduce overload - which is a factor of performance - you are encountering too much RF of a signal in close proximity - distorting the overall general input the receiver is trying to use - against a signal that you are trying to hear - that is lost forever due to the ambient distortion the receiver input has produced because of those stronger signals have clamped and forced the RF input section to over amplify and distort the entire signal.
So RF Gain as itself can provide an extra tool in the toolbox of your radios receiver performance to lessen noises and signals both in and around your listening or working frequency - to let the radios own selectivity to help you find what you wanted to hear and work - by reducing sensitivity so selectivity prevails.
Squelch doesn't do that, it simply quenches all the input signal both strong and weak - by quieting the speaker. When a strong signal on the frequency you are listening to - appears - that circuit then stops the quenching and opens the line from the detector that has all the audio the receiver has picked up - you hear thru the speaker. The quenching is adjustable so you can hear the signal to tailor to your needs - if it were to fade - or if the user was away on an errand using their radio - you can set the squelch to open - or break - to let you know and perceive the users proximity to your station by the signal strength it is able to break the squelch open with.
Hope this helps!
