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FLEX-6000 Signature Series – Maestro User Guide

Operating with AGC turned OFF may be desired by operators who want to avoid having a strong

signal drive a weak nearby signal into the noise floor resulting from AGC audio attenuation. Digital

mode operation may benefit from this configuration.

To adjust the AGC Threshold, tune to a quiet spot between stations. Starting with the AGC-T at a

high value decrease the AGC-T until the background noise just begins to decrease. This is the AGC-

T "sweet spot" or the "knee" of the AGC algorithm. Depending on band conditions, if the AGC-T is

set below 50, you may have to compensate for the loss in audio gain (volume) by increasing the

Slice volume to a higher value. When you get the knee and AF volume adjustment correct for the

band conditions, it will keep the volume of strong signals constant which will allow weaker signals

to be heard even with AGC in FAST mode. Thus AGC-T is one of the most important adjustments,

and often overlooked, to achieve the maximum weak signal receive performance out of the FLEX-

6000 series SDRs.

The Automatic Gain Control Threshold (AGC-T) adjustment is located on the AF/AGCT/SQL multi-

function control. Each Slice Receiver has its unique settings for the AGC timing and threshold.

The AGC attack/release time is controlled by the AGC button on the Slice Receiver Menu. You can

choose FAST, MEDium, SLOW, or OFF.

14.2 DSP NOISE MITIGATION FEATURES

The Slice Receiver Menu contains the enable buttons and threshold adjustments for the Wideband

Noise Blanker, Slice Specific Noise Blanker, Noise Reduction, and Automatic Notch Filter. The

midrange settings of the threshold controls are good starting points for adjustments.

14.3 WIDEBAND NOISE BLANKER (WNB)

The Wideband Noise Blanker (WNB) is used to combat fast rise time pulse-type noise such as power

line hash and car ignitions. To enable the Wideband Noise Blanker, tap the WNB button, then

adjust the threshold control for the best noise suppression. In general, the default setting is

adequate, but depending on the noise characteristics, some adjustments can help. The WNB

Threshold control adjusts the level at which a sample is considered to be impulse noise. The general

rule of thumb for this adjustment is to use the lowest level that is effective. For large impulse noise

(meaning the noise floor jumps are large) a lower level should be used. If the impulse noise is

causing only small jumps in the noise floor, a higher level can be used.

Large signals, both in the passband and around it, can result in distorted audio if the WNB threshold

control is set too high.

Since the Wideband Noise Blanker operates at the Panadapter level rather than at the Slice level

easy detection of wideband correlated noise pulses is possible. The algorithm employs an

automatic slider normalization function to make the WNB work consistently on different

bandwidths and signal levels. This unique architecture allows pulse removal with far less distortion

than many traditional noise blankers.

FlexRadio Signature FLEX-6000 Series User Manual

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