AGC again Not AGC-T

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  • Updated 5 years ago
I have asked about this before but all you folks do is explain how to set up AGC-T

I don't have a problem with that.  It seems that when I am listeniing to a weak station and then a

strong station comes on the volume gets so loud and a the agc does not cut back     it makes it very uncomfortable trying to ride the volume control up and down   appreciate any help with this    I tried my Icom 7600 on the same stations and it works great.  I am using the 6500


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Posted 5 years ago

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KY6LA - Howard, Elmer

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my best guess it that you have your AGC-T set too high

I usually run mine around 40-45
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Tom Warren

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   Thanks for the tip about the 500hz EQ setting, I never thought about that. After reading your post I went right out to the shack and tried it. Made a slightly noticeable difference........another tool in the cw toolbox :)

  Really looking forward to the release of v1.5, and the weak signal enhancements. 

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Ken - NM9P

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Just remember that every time you add something like the RX EQ 500 Hz boost, or the APF filter, or change the preamp setting, you need to readjust the AGT-T because each one of them will move the "Sweet Spot" or "Knee" in the process.  Having the AGC-T on the FlexControl Knob is very handy in this case....  This is a hotrod rig, but sometimes you have to drive it like a manual shift Corvette.
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Barry N1EU

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"Actually, it sounds to me that you are setting the AGC-T too LOW, and turning the volume up loudly so you can hear the weaker stations. Then a station that is stronger than the AGC threshold comes in and blasts you."

This doesn't make sense to me.  I think you meant to say "AGC-T too HIGH, and turning the volume up loudly so you can hear the weaker stations."  Then a strong station comes in and AF output rises dramatically and blasts you.

Barry N1EU
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Ken - NM9P

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If by "high" you mean too far to the left, then, yes. My internal terminology is..right high, left low! In AGC-T, that is probably backwards.... It is probably the only control in SSDR that is that way.
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Pat - WH6HI

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I usually set AGC-T by listening to the weakest station, then adjusting either left or right until the volume is right for your ears.  It may also be necessary to adjust the volume control for comfortable level.  With the AGC-T set for the weak station the strong one will be adjust and should be about the same volume. 
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IW7DMH, Enzo

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It happens to me when I set accidentally a low gain on my amplified speakers (Bose Companion 2). So I tend to set slice volume and master volume very high (over 90-95%).Try to set master and slice volume to 80% and then give more gain to your amplified speaker.
Also, when strong stations come near the weak ones, a wide TNF could help a lot.
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Ken - NM9P

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I always use master volume on max, and slice volume on one-half. I use the speaker's volume control to make up the difference.

I have never had this problem, except when I had the AGC in OFF position for digital and forgot to change it . . . OUCH! I usually find that with slice volume on half, that the headphone volume on one-half is a ought right for me.
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Bill -VA3WTB

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I do that too Ken, master at full, and I control volume with the AGC. never miss a weak signal.
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Ken - NM9P

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I also usually have the AGC-T ported to the AUX2/center button on my FlexControl Knob so that I can quickly adjust it as I S&P in a contest.  AUX1 either controls RIT or Sends my Call in CW.  AUX3 either controls XIT or sends my contest exchange in CW.  That is what works for me.  The beauty is that the FlexControl is customizable, to some degree, and will receive more flexibility in the future..

Now that I have moved to N1MM+ for contesting, I usually use the FlexControl for RIT/XIT.
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Jay / NO5J

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I've got the AGCT level assigned to the left button on the Flexcontrol, Slice volume on the middle button, VFO assigned to the knob. master volume stays on max. Volume control on my speakers substitutes for the master slider. It makes it simple to ride the AGCT and slice volume. Had to assign the knob to do something might as well do the same for my left hand. Adjusting the AGCT now allows my left hand to have a purpose in life, when I gave up smoking and lefty no longer felt useful, he more than any other body part, really craved holding on to cigarettes, he just hung there at the end of my arm, just like a left hand, nearly useless. Now he's started adjusting, I guess left hands have feelings too.

73, Jay - NO5J
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Tim - W4TME, Customer Experience Manager

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The AGC system in SmartSDR is a dual track system; meaning that it can track both slow and fast increases in signal gain, making appropriate gain correction decisions in the presence of each.  The speed of the AGC (FAST, MED, SLOW) sets how quickly or slowly the AGC recovers after a strong signal.  You can easily hear this by tuning into 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.

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, then, provide faster levels of recovery for when you want the system to more 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 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 rate that is less distracting.  If the User 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, this means that 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 adjust the AGC-T to the right, the more gain is applied and the louder the signal and noise will be.  The benefits of increasing SNR with AGC will be lost in this mode.  The other down side of turning AGC off is that the operator must to pay attention to the 'RF Gain' manually to avoid distortion due to overload by strong signals. 

Operating with AGC turned OFF is desired by operators who want to avoid having a strong signal drive a weak nearby signal into the noise floor resulting from AGC audio gain reduction, such as when operating digital modes. 

The Automatic Gain Control Threshold (AGC-T) adjustments are located with the slice audio controls; it is the bottom control in the audio panel.  Each slice receiver can have its own settings for the AGC timing and threshold.

The proper setting for the AGC threshold is determined by the band noise and the signal strength of the desired signal.  Reducing the threshold can significantly improve the signal-to-noise ratio of the desired signal.  Increasing the threshold will increase the gain in the receiver, which is sometimes necessary for weak signals.  Properly adjusted, you can virtually eliminate band noise and have a very clean signal that is very pleasant to hear.  

To adjust the AGC Threshold, tune to a quiet spot between stations and adjust the AGC-T slider to the left (lower gain values) until the background noise just begins to decrease.  This is the AGC-T "sweet spot" or "knee" of the AGC algorithm.  When you get the knee adjustment correct for the band conditions, it will make the signals come up out of the noise, even with AGC in FAST mode.  This 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.
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Thanks everyone that responded

I will give all a try

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Alex - DH2ID, Elmer

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Thanks, Tim. Best explanation found here.
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Thanks Tim, GREAT explanation.