Automatic Gain Control

Some channels in systems come in with audio louder than the rest, how do you set the AGC for these systems?

AGC for BCD536HP

bobcat said:

Some channels in systems come in with audio louder than the rest, how do you set the AGC for these systems?

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The 436 and 536 have both analog and digital AGC circuitry. But my experience has been (and as many others on the forums have noted), setting the AGC on or off seems to make very little, if any difference, in the performance of the radio.

Even when set to "on", some signals still come in louder than others. The AGC seems to be mostly ineffective in these Uniden scanners.

I have tried using AGC on every scanner I had that had it and never noticed any difference. Even on our new state P25 system which has some extreme variations in volume. It just seems to depend on the person talking.

W8RMH said:

I have tried using AGC on every scanner I had that had it and never noticed any difference. Even on our new state P25 system which has some extreme variations in volume. It just seems to depend on the person talking.

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Agreed; I've seen the same thing. I did notice that careful use of the Audio Boost setting on my RS scanners does help a little.

OP, if you really want to tame it, you might consider piping the scanner audio through a hardware compressor. A hardware compressor won't make it all perfectly level, but when set right it can noticeably reduce the volume level variations and make listening more pleasant.

flythunderbird said:

Agreed; I've seen the same thing. I did notice that careful use of the Audio Boost setting on my RS scanners does help a little.

OP, if you really want to tame it, you might consider piping the scanner audio through a hardware compressor. A hardware compressor won't make it all perfectly level, but when set right it can noticeably reduce the volume level variations and make listening more pleasant.

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This ended up being my solution to taming down widely varying audio levels. I've used various audio devices made for pro audio setups such as found in recording studios. That can get expensive real fast though but has given me the results I was after.
I had a buddy that worked at a studio. He gave me a bunch of older rack mount equipment when they changed their studio for more digital equipment from older analog gear. Some of it is even vacuum tube devices!

As has been mentioned, the various AGC settings offered in many scanners seem to be more like snake oil and don't seem to do anything.
Leveling human speech can be hard though as you could end up knocking out a part of a transmission you want even when using audio gear found in a recording studio.
I could usually find a setting that did not blast out sleeping people when a loud transmission popped up but in almost all cases, it did require pro quality audio gear to even come close.
I often wonder if the so called AGC settings in some of todays scanners even do anything. They usually don't seem to offer any change detected by ear but perhaps it could be seen with a scope! Kind of overkill for a scanner radio though. Of course my old ears are not near as sensitive as they were many years ago but I sure do notice the level changes from various dispatchers that seem to speak into the mic from 5 feet at times only to come back a few seconds later with what sounds like they are speaking into the same mic only a few inches from their mouth!
You almost need a hardware compressor that adds enough delay to process and level the audio before it comes out your speakers.
Some of todays digital compressors do just that and do pretty good at it as well.
I like to feed between 12 to 16 radios into a mixer and then level the audio after the mixer but the darn leveler turns down a radio a may have wanted to boost when I heard interesting traffic. It would be better to have a leveler for each radio and feed those outputs into a mixer but that can take money and space!

I use an old Innovonics 222 that was retired from AM broadcast service on my feed. It's certainly not state of the art but seems to work well for the feed.

My guess on the AGC is that it is more for RF gain control than audio level control. In AM it could make a big difference in audio level but in FM and especially Digital it will has not made much difference in my experience. A very weak digital RF signal sounds just as loud as a very strong digital RF signal.

I do not know how helpful the AGC is for “selectivity” considerations in limiting the amount of amplification of an already strong RF signal (in things like overloading the radio RF circuits).

As one other poster mentioned I too use the audio level control of +3 to -3 (I think) on different channels and it seemed to really help.

bobcat said:

Some channels in systems come in with audio louder than the rest, how do you set the AGC for these systems?

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You could try using the volume offset setting... It will let you do a -3 to +3 offset and see if that helps.
You can do that on a per/channel basis...

N0UDG said:

My guess on the AGC is that it is more for RF gain control than audio level control. In AM it could make a big difference in audio level but in FM and especially Digital it will has not made much difference in my experience. A very weak digital RF signal sounds just as loud as a very strong digital RF signal.

I do not know how helpful the AGC is for “selectivity” considerations in limiting the amount of amplification of an already strong RF signal (in things like overloading the radio RF circuits).

As one other poster mentioned I too use the audio level control of +3 to -3 (I think) on different channels and it seemed to really help.

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I thought the Attenuator feature was more for RF control than AGC.

N0UDG said:

................. As one other poster mentioned I too use the audio level control of +3 to -3 (I think) on different channels and it seemed to really help.

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Several scanners have this +/- option. Actually works. AGC, can't see any effect, but that could be me, lol.