Gain is the amplification of an audio signal.
The amount of amplification is measured in voltage.
So, if your audio source has 1 volt and you are amplifying by +10 db , then your output will be 11 volts (1 x 10 ).
You need to amplify to match the output of your source.
For example, if you have a weak signal from a dynamic microphone and need to connect it to a mixer (which requires an XLR mic input) then you will need to add amplification.
What is gain and where does "gain" come from in the first definition?
In some cases, a linear amplifier or attenuator is called a "gain" because it changes the voltage by an amount that's roughly proportional to the change in current (or sound level).
If an amplifier has 10 dB of gain when measured on its output terminals, a 1-V input signal will result in an approximately 10 V signal at its output terminals—a 10x difference. But this isn't what most electronics people really mean when they talk about gain.
They usually mean electrical power, not acoustical gain. The confusing thing is that audio transformers don't have their own power supplies.
Well ideally you'd have infinite gain in both directions so that your transmitted RF waves were reflected back toward you just like light reflects off a mirror at an equal intensity. In practice however this never happens because there are always some losses associated with all antennas no matter how strong they are.
You may like: Antenna Gain vs Distance - Explained.
The amount of gain provided by an antenna is measured in "db" or decibels which have a logarithmic relationship to the power that is being transmitted and received. So a 3db increase will double your output power while also doubling the amount of noise and interference you'll hear at the same time.
An important thing to keep in mind about "Gain" is that it is usually specified as being either "dBi" (for isotropic) or more commonly for mobile applications, it's rated as dBd.
In practice, dBd figures are generally much smaller compared to dBi values, but this isn't something you need to worry about. Most handhelds are perfectly fine with either figure as long as they're in the positive direction (i.e. dBd gain).
For reference, a typical mobile handset will transmit at roughly 30dbm (1 watt) which doesn't give you much room to increase your output power when using a directional antenna like an 18" Firestik.
So what does this mean in real-world situations? Depending on your operating frequency, the amount of noise around you, and weather conditions it will take roughly 3-5db of increased gain to notice a difference in signal strength.
Likewise, if a handset has +3db built into its system there's likely no need for an external antenna at all because bare minimum if everything adds up right then a resulting +6db should be enough to get your signal out there.
How do I set the gain on my microphone?
Each brand of the microphone has a different method for selecting gain. If you don't know what to look for, it can be somewhat confusing.
In most cases, the gain level will be set via a continuously variable potentiometer which is commonly referred to as "trim" pot .
Below is an example of one such pot used on a Kenwood microphone:
Setting the trim correctly may have no effect at all while not setting it properly could result in your transmitted signal being greatly reduced or even clipped off completely if too much gain is applied.
If you are having difficulty finding how to change your gain setting, we would suggest contacting whoever designed the microphone system that you purchased.
You may like: Best CB Microphones
What happens if the gain is too high or too low?
If the gain is set too low your radio will transmit in a very low power state that could be as low as 10-20 watts. This will result in weak signals and potentially other issues associated with being "LOCAL ONLY".
If the gain is set too high, there are several potential problems that could arise:
1. Your transmitted signal may be clipped resulting in a hot over modulated audio recording.
2. You may detect excessive background noise or even intermittent high-pitched squealing sounds from within your own system depending on how you have everything tuned/installed.
3. With an improperly adjusted microphone it's possible to damage either your radios or microphones' internal electronics if output powers exceed 100+ watts.
What about gain on 8Pin vs 4Pin microphones?
In recent years 8 pin "smart" mics have become popular with manufacturers such as Kenwood, Icom, and Yaesu. Some examples of this include the PG series radios from Icom or the VX6 line of handhelds from Yaesu.
Smart mics are generally compatible across nearly all platforms and brands so you can take your microphone over to someone else's house and plug it right into their radio without issue. You can even get most smart mic systems for relatively cheap when compared to their standard non-smart counterparts.
The only real downside is that they're somewhat harder to tune since there aren't any knobs available on the mic itself to adjust levels (such as gain).
Microphone gain vs volume
Gain and volume are two different things.
The difference between gain and volume is gain is the amount that controls the level of your mic and how much signal it sends to your radio while volume is the same thing but for audio being heard by you, or a listener's headset/speakers.
They often share volume knobs but can sometimes be separate on some radios too.
Every radio brand and model is different but generally, there are two basic types of radios that use a rotary control (either a knob or switch) for changing volume.
The first is either an analog system where changes in the volume setting correspond with changing levels of audio which is sent from the transceiver to your speaker/headset - the volume knob.
These can be adjusted via knobs if set correctly but often come pre-tuned so that increasing or decreasing volume will make no difference to quality whatsoever resulting in a fixed level of loudness regardless of how much amplification has been applied.
The second and slightly newer type is referred to as a digital system. In these radios, the volume knob could correspond with either both analog and digital circuits or just one.
In these cases, there are two separate gains associated with the volume knob.
One gain for the audio circuit which corresponds to how loud your speaker will be, and another gain value applied post-digital processing of signals that are used for modulation purposes so that you don't clip off your signal if it's too strong resulting in distortion/clipping in your recorded file.
It's important to know the difference between gain and volume as these settings depend on what type of radio you're using (analog vs digitally controlled) different approaches may be needed when setting up gain levels on microphones.
"I'm new to this stuff... what should I do?"
If you've never dealt with microphone gain before or aren't sure where it is on your particular radio, we would suggest checking out the manufacturer's guide for that specific model. If you don't have one of those, or can't understand it then here are some basic steps you can take:
List of Steps
Try connecting a known-good set of headphones/speakers directly into the "audio output" port on any rear panel jacks that exist.
Then bring up any channel or signal source and increase its volume until you hear sound coming through them.
Make sure they're not muted by mistake!
After that leave them connected while following these next steps since all three will be done simultaneously!
Bring up your microphone and press the PTT (push to talk) button.
Using a VOX-capable radio if available, if not just key the mic by pressing down on the push button, then slowly increase volume in small increments while watching for audio levels both from your speakers/headphones as well as monitoring in real-time.
If you've got a smart microphone this will be easier because once it's been tuned you should see no change at all when adjusting gain settings and just adjust them until their output looks right. If using an analog system without knobs then bringing up or lowering your volume control should make changes to your audible signal's loudness but going above zero or below negative infinity should result in no change at all.
If you're using a digitally controlled radio then remember it might have different settings on the front panel or menu that are used for VOX activation and not volume!
Once this step has been completed, switch to any channel that isn't already being monitored by your computer (either temporarily mute the signal from it with another programmed button or just move on to the next one).
Slowly adjust the gain on your microphone in small increments until your sound level doesn't clip off above negative infinity (or zero if analog) when adjusted past its highest output level either through FSVUtl (if having issues get help here ) or using Windows built-in audio mixer.
Negative infinity for most is just barely above the highest frequency your voice can emit, but depending on your microphone it may be different so make sure to check!
Now you need to decide if you want to adjust one or both of the gains in your radio depending on what type it is.
If using an analog system with volume knobs then you'll have several gain stages where increasing each will increase the loudness of audio and decreasing them will do the opposite. It's important that neither reach 0 dB since this would mean clipping so try to keep within 10-15 dB max and always ensure positive infinity isn't being clipped either (or below zero if using a digitally controlled radio).
With these types of radios it's possible to get lossless audio but at the cost of increased noise as the gain is increased. This can be too much of a hassle sometimes if you're just using your radio to listen to others so finding the right balance is key!
Repeat this process on different channels/signals until you've got a good baseline for what sound levels should look like while adjusting the microphone gain in small increments, or at least know how far to turn it up before clipping occurs and if it does what level that happens.
How do you set the RF gain on a CB radio?
With most radios (CB/HAM) you'll have a set of gain controls that can be labeled as the "PA" or some other acronym on the front.
On many digital models, these are controlled through their menu system and not knobs so while they're often listed under Gain, AGC, or AVC they may control something else entirely like microphone volume, VOX thresholds, interference reduction settings, etc.
If your radio doesn't have this then it's usually not worth using as a main scanner for various reasons I won't go into here.
If your CB has them then use those but if not there is also another way to adjust RF gain:
List of Steps
Bring up any channel that isn't being used for live monitoring and then adjust the tuning controls on your radio until it's clear.
Slowly increase volume by turning up microphone gain until you start hearing static, then reduce in small increments and listen for both a decrease in noise as well as audio distortion. If using a digital control model use the menu to check or trial-and-error method.
If there is no change when increasing audio input signals then turn down RF gain. This is important because if you can't hear someone else talking (especially with a weak signal) this means they'll most likely miss what you have to say too!
On an analog set turn down the RF gain knob instead or use an external attenuator that comes after the antenna connector (not before since that can cause issues).
Once you've got your levels set, switch to a different channel and repeat the process until it works well (noise/distortion is reduced with no clipping) on all but the very weak signals since they usually won't be loud enough for a proper adjustment anyway.
If using an external antenna amplifier or line-of-sight radio may drastically increase both signal and noise levels so fine-tuning can take more time before getting it right!