To Next Page

To Previous Page

FLEX-6000 Signature Series – Maestro User Guide

14 HOW TO CONFIGURE NOISE MITIGATION

The FLEX-6000 Series radios have several digital signal processing functions that enhance reception

in noisy environments.

14.1 AGC THRESHOLD

Automatic Gain Control (AGC) is a feature that automatically adjusts the Slice Receiver’s audio gain

(volume) based on the strength of signals in the receiver’s passband filter. The goal of AGC is to

amplify weak signals and attenuate strong signals so that they all lie within a comfortable listening

range.

The receiver Automatic Gain Control Threshold (AGC-T) can be adjusted for optimum performance

in noisy or quiet environments. The AGC-T sets the maximum gain applied under any

circumstances. Since the noise floor is relatively constant on a given band at a given time, the AGC

can be adjusted using the threshold control so that the AGC never applies gain to noise, but it will

apply gain to signals just out of the noise. In doing so, the AGC can reduce the level of noise you

hear, and help signals pop out of the noise.

The AGC system is a dual-track system, meaning that it can track both slow and fast increases in

signal strength, making appropriate gain correction decisions in the presence of each. The speed of

the AGC (FAST, MED, SLOW) determines how quickly or slowly the AGC recovers after attenuating a

strong signal. You can easily hear this by tuning to a CW signal and going through the three

settings. On FAST with a strong signal, you can hear the gain pump up and down while on SLOW it

recovers after a longer pause once the signal stops. When the signal stops, you will hear the noise

floor increase as the gain returns.

How to Set AGC for Different Operating Conditions

If you are listening to a loud voice signal, AGC SLOW will resist increasing the gain between syllables

and therefore reject most of the noise which is at a level far below the signal. FAST and MED

provide faster levels of recovery for situations when you want the system to closely follow the

dominant signal in the passband. Any time you have a very strong signal that causes the gain in the

AGC to be reduced, you could experience a loss of gain to a weak signal you are listening to. The

filter passband edges, which are continuously adjustable, and TNFs can be used to eliminate signals

that might interfere with AGC operation.

The operator might prefer to use SLOW settings when rag chewing in a high signal-to-noise

environment where there isn't much QRN and the noise floor is stable. This keeps the gain at more

of a constant level that is less distracting. If the operator is trying to pull a weak CW signal out of

the noise, they may prefer to use FAST mode to quickly ensure that the long-term average of the

noise floor doesn't overcome the signal and prevent it from being heard. MEDium is a reasonable

compromise.

When AGC is set to OFF, a fixed amount of gain determined by the AGC-T setting will be applied to

both fast and slow signals regardless of their level. The more you increase the AGC-T, the more

gain is applied and the louder the signal and noise will be. The benefits of increasing SNR with AGC

are lost in this mode. Another disadvantage of turning AGC off is that the operator must adjust the

'RF Gain manually to avoid distortion due to overload by strong signals.

FlexRadio Signature FLEX-6000 Series User Manual

Questions and Answers: