pcr-2500 agc

[updatelee]

Im quite new to this, my previous scanners have been much simpler, ie pro-95 and pro-2022

I noticed in the manual the AGC button, this sounds like it would be really nice as depending on who is speaking the volume is quiet or loud, some people just seem to whisper into the mic, lol.

when I click it I hear the soft beep meaning it didnt take into effect, and it doesnt get highlighted. Is this because the freq im listening to is in FM mode ? the manual only mentions AM and SSB. how come AGC wont work on FM ?

 

[steve_s]

Im quite new to this, my previous scanners have been much simpler, ie pro-95 and pro-2022

I noticed in the manual the AGC button, this sounds like it would be really nice as depending on who is speaking the volume is quiet or loud, some people just seem to whisper into the mic, lol.

when I click it I hear the soft beep meaning it didnt take into effect, and it doesnt get highlighted. Is this because the freq im listening to is in FM mode ? the manual only mentions AM and SSB. how come AGC wont work on FM ?

The AGC in a receiver is the automatic gain control of the RF / IF stages. It only has minimal effect on the audio signal. The only time you hear a significant change in the audio level (for a given percentage of modulation amplitude) is when the AGC has reached it's lower limit and is "running out of steam" (i.e. the receiver is running with maximum gain, and any further decrease in signal strength at the antenna will decrease the AF output signal.. There are special Audio AGCs. They would accomplish the constant amplitude in the voice signal. However, this circuitry is not normally incorporated in Amateur / Consumer receivers.
Since an FM signal is heavily limited before it reaches the demodulator, there is no need for an AGC. The signal out of the limiter will always be constant. The absolute amplitude of this signal will be determined by the sensitivity of the system, at the lowest acceptable RF signal level. So, any increase in RF level will just increase the limiting action, without changing the demodulated (audio) signal level. How loud someone sounds is determined by the frequency deviation, rather than the amplitude of the RF signal.