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An AGC story

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Cady, Fred

An AGC story

After Team Vertical got back from our latest adventure in C6land, I was
curious about how the AGC was working (or not). Kenny, C6ATA came away
from the event really preferring his venerable TS850. Both Walt, C6ATR
and I, C6AKX found turning AGC off was a way to increase the "depth" of
the pileup and continue to rapidly pull signals out.
I made some measurements and have posted the results for your perusal
and information at www.ke7x.com.

73,
Fred
Ke7x
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Joe Subich, W4TV-4

Re: An AGC story

Fred,

For more on the K3 AGC system, please see the excellent study
by Jack Smith, K8OZA at:
http://cliftonlaboratories.com/elecraft_k3_agc_and_s-meter.htm

Careful study of Jack's tables would tend to support your belief that
the K3 could benefit from a higher threshold setting. Comparing the
behavior of the K2 to that of the K3 as shown in Jack's charts, shows
support for a threshold of some 20 dB higher than the present -100 dBm
(~S4) that K8OZA measured for THR=8. That would place the threshold
around S8 (-79 dBm) similar to that shown by the K2.

73,

... Joe, W4TV

On 12/8/2010 8:01 PM, Cady, Fred wrote:

> After Team Vertical got back from our latest adventure in C6land, I was
> curious about how the AGC was working (or not). Kenny, C6ATA came away
> from the event really preferring his venerable TS850. Both Walt, C6ATR
> and I, C6AKX found turning AGC off was a way to increase the "depth" of
> the pileup and continue to rapidly pull signals out.
> I made some measurements and have posted the results for your perusal
> and information at www.ke7x.com.
>
> 73,
> Fred
> Ke7x
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>

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Barry N1EU

Re: An AGC story

In reply to this post by Cady, Fred

Cady, Fred wrote

I made some measurements and have posted the results for your perusal
and information at www.ke7x.com.

Very interested findings - Fred has a graph of AGC action with AGC THR=8 labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story :

So I ask this group: is it possible to raise the AGC Threshold from s3 to s6 or s9 by simply reducing the RF Gain control? Can anybody estimate what settings of the RF Gain control would accomplish that?

Barry N1EU

Don Wilhelm-4

Re: An AGC story

Barry,

Without doing any measurements it may be difficult to say precisely, and
I would think there would be a bit of difference from one K3 to another.

However, there is a quick and easy way to accomplish that - note that
the S-meter increases as the RF gain is reduced. So if you want to
increase the AGC Threshold by (say) 3 S-units, disconnect the antenna,
and reduce the RF Gain until you move the no-signal S-meter up by 3
S-units. That should be close to your goal.

73,
Don W3FPR

On 12/9/2010 9:07 AM, Barry N1EU wrote:

>
> Cady, Fred wrote:
>> I made some measurements and have posted the results for your perusal
>> and information at www.ke7x.com.
> Very interested findings - Fred has a graph of AGC action with AGC THR=8
> labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story :
>
> So I ask this group: is it possible to raise the AGC Threshold from s3 to s6
> or s9 by simply reducing the RF Gain control? Can anybody estimate what
> settings of the RF Gain control would accomplish that?
>
> Barry N1EU
>

Joe Subich, W4TV-4

Re: An AGC story

In reply to this post by Barry N1EU

> Very interested findings - Fred has a graph of AGC action with AGC
> THR=8 labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story :

That graph is nearly identical to the information that Jack Smith,
K8OZA originally presented two years ago:
http://cliftonlaboratories.com/elecraft_k3_agc_and_s-meter.htm

The following table comes from Jack's work:

> From the data, my estimate of the threshold settings is:
>
> AGC THR Corresponding Input
> Signal Level
> 2 -117 dBm
> 3 -110.5 dBm
> 4 -105 dBm
> 5 -103.5 dBm
> 6 -102.5 dBm
> 7 -101 dBm
> 8 -99 dBm

The K2 AGC curve is also presented for comparison. K2 does not
have a well defined threshold like that of the K3 but some AGC
action (the curve departs from 1:1) begins at around -85 dBm and settles
at slope similar to the K3 SLP=09 or SLP=10 (about 1.5 dB
audio change for 10 dB RF change) at an RF level around -70 dBm.

As a second point of comparison, Sherwood's Receiver Performance Table
shows the FT-1000D has an AGC threshold nearly 10 dB higher than the
K3 *with the FT-1000D preamplifier enabled*. Since the FT-1000D
preamp is at least 10 dB, that represents an overall 20 dB higher
ACG threshold (around S8/S9 with preamp off and S6/S7 with preamp on).

It seems clear that the K3 would have much better "pile-up performance"
if range of AGC THR were expanded by as much as 20 dB either by
increasing the "step" (5/6 differ by only 1 dB) or by increasing
the number of options.

73,

... Joe, W4TV

On 12/9/2010 9:07 AM, Barry N1EU wrote:

>
>
> Cady, Fred wrote:
>>
>> I made some measurements and have posted the results for your perusal
>> and information at www.ke7x.com.
>>
> Very interested findings - Fred has a graph of AGC action with AGC THR=8
> labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story :
>
> So I ask this group: is it possible to raise the AGC Threshold from s3 to s6
> or s9 by simply reducing the RF Gain control? Can anybody estimate what
> settings of the RF Gain control would accomplish that?
>
> Barry N1EU
>

Barry N1EU

Re: An AGC story

In reply to this post by Don Wilhelm-4

Thanks Don. I just realized that I can do some quick experiments to get my
answer using an XG2's s3/s9 capability and noting audio level increase with
AGC Off and then with AGC On and reducing RF Gain until same audio increase
is accomplished.

An aside to KE7X and W4TV: I too wish we could try experimental firmware
that significantly raised the max AGC THR value.

And to K6LL: Yes, I too fear loss of weaker signals

73, Barry N1EU

On Thu, Dec 9, 2010 at 3:00 PM, Don Wilhelm <[hidden email]> wrote:

> Barry,
>
> Without doing any measurements it may be difficult to say precisely, and I
> would think there would be a bit of difference from one K3 to another.
>
> However, there is a quick and easy way to accomplish that - note that the
> S-meter increases as the RF gain is reduced. So if you want to increase the
> AGC Threshold by (say) 3 S-units, disconnect the antenna, and reduce the RF
> Gain until you move the no-signal S-meter up by 3 S-units. That should be
> close to your goal.
>
> 73,
> Don W3FPR
>
> On 12/9/2010 9:07 AM, Barry N1EU wrote:
>
>>
>> Cady, Fred wrote:
>>
>>> I made some measurements and have posted the results for your perusal
>>> and information at www.ke7x.com.
>>>
>> Very interested findings - Fred has a graph of AGC action with AGC THR=8
>> labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story :
>>
>> So I ask this group: is it possible to raise the AGC Threshold from s3 to
>> s6
>> or s9 by simply reducing the RF Gain control? Can anybody estimate what
>> settings of the RF Gain control would accomplish that?
>>
>> Barry N1EU
>>
>>

Cady, Fred

Re: An AGC story

Thanks Barry for the suggestion to run some curves while changing the RF
gain position. I've done that and I'm not sure I understand what is
going on yet. Need to think about it a bit. I'll post the curves up on
ke7x.com in a while.
Fred

Fred Cady
fcady at ieee dot org

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Barry N1EU
> Sent: Thursday, December 09, 2010 8:11 AM
> To: [hidden email]
> Subject: Re: [Elecraft] An AGC story
>
> Thanks Don. I just realized that I can do some quick
> experiments to get my
> answer using an XG2's s3/s9 capability and noting audio level
> increase with
> AGC Off and then with AGC On and reducing RF Gain until same
> audio increase
> is accomplished.
>
> An aside to KE7X and W4TV: I too wish we could try
> experimental firmware
> that significantly raised the max AGC THR value.
>
> And to K6LL: Yes, I too fear loss of weaker signals
>
> 73, Barry N1EU
>
> On Thu, Dec 9, 2010 at 3:00 PM, Don Wilhelm
> <[hidden email]> wrote:
>
> > Barry,
> >
> > Without doing any measurements it may be difficult to say
> precisely, and I
> > would think there would be a bit of difference from one K3
> to another.
> >
> > However, there is a quick and easy way to accomplish that -
> note that the
> > S-meter increases as the RF gain is reduced. So if you
> want to increase the
> > AGC Threshold by (say) 3 S-units, disconnect the antenna,
> and reduce the RF
> > Gain until you move the no-signal S-meter up by 3 S-units.
> That should be
> > close to your goal.
> >
> > 73,
> > Don W3FPR
> >
> > On 12/9/2010 9:07 AM, Barry N1EU wrote:
> >
> >>
> >> Cady, Fred wrote:
> >>
> >>> I made some measurements and have posted the results for
> your perusal
> >>> and information at www.ke7x.com.
> >>>
> >> Very interested findings - Fred has a graph of AGC action
> with AGC THR=8
> >> labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story :
> >>
> >> So I ask this group: is it possible to raise the AGC
> Threshold from s3 to
> >> s6
> >> or s9 by simply reducing the RF Gain control? Can anybody
> estimate what
> >> settings of the RF Gain control would accomplish that?
> >>
> >> Barry N1EU
> >>
> >>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Buck - k4ia

Re: An AGC story

In reply to this post by Cady, Fred

As I understand the graphs and operation:

AGC Threshold is the point at which AGC action starts. The higher the AGC
THR number, the higher point at which AGC starts. The highest AGC THR (8)
starts AGC action at S3. That is a pretty low level but any setting less
than THR 8 starts the AGC action with even less signal.

AGC SLP is how aggressive the AGC action is as signals rise. A highest
AGC SLP number means the AGC flattens everyone. AT SLP = 15 all signals
above S3 are brought to roughly the same level. Heard one at a time, two
signals - one at S3 and one at S9 will sound the same level.

But, since AGC works on every signal in the passband, if there are two
signals - one S9 and the other S3 appearing at the same time, the S3 signal
will disappear because the AGC is knocking down the S9 signal to an S3 level
and thereby also reducing the S3 signal to the noise. Using a less
aggressive (lower) slope number will help but the dynamic range between and S3 and
S9 signal is compressed. The core problem is the AGC starts at such a low
level. Background noise alone on 80 - 40 is almost always more than S3.

The suggestion is an AGC THR setting to allow higher than an S3 level
before AGC action starts. That makes sense but does it start to degrade the
high-end dynamic range of the radio? Are we in danger of overloading the
intermediate amplifiers/mixers generating IMD and other unwanted issues?
Seems like there is a balancing act here.

Another way to accomplish this is to use the Attenuator and/or reduce the
RF gain to reset our starting point so that the S5 signal at the antenna
becomes an S3 signal at the AGC level and our AGC action doesn't really begin
until S5. I would like the ability to switch in even more attenuation for
high noise conditions. Can that be done through the software?

Still I would like to try a higher AGC THR setting and see how it plays.
The beauty of this radio is its ability to adjust to different conditions -
one size does not fit all. Unfortunately, its also complicated. It has
taken me three years to figure this little bit out.

Comments? Do I understand it right?

Buck
k4ia
K3 #101

In a message dated 12/9/2010 10:11:19 A.M. Eastern Standard Time,
[hidden email] writes:
Thanks Don. I just realized that I can do some quick experiments to get my
answer using an XG2's s3/s9 capability and noting audio level increase with
AGC Off and then with AGC On and reducing RF Gain until same audio increase
is accomplished.

An aside to KE7X and W4TV: I too wish we could try experimental firmware
that significantly raised the max AGC THR value.

And to K6LL: Yes, I too fear loss of weaker signals

73, Barry N1EU

On Thu, Dec 9, 2010 at 3:00 PM, Don Wilhelm <[hidden email]> wrote:

> Barry,
>
> Without doing any measurements it may be difficult to say precisely, and
I
> would think there would be a bit of difference from one K3 to another.
>
> However, there is a quick and easy way to accomplish that - note that the
> S-meter increases as the RF gain is reduced. So if you want to increase
the
> AGC Threshold by (say) 3 S-units, disconnect the antenna, and reduce the
RF
> Gain until you move the no-signal S-meter up by 3 S-units. That should
be

> close to your goal.
>
> 73,
> Don W3FPR
>
> On 12/9/2010 9:07 AM, Barry N1EU wrote:
>
>>
>> Cady, Fred wrote:
>>
>>> I made some measurements and have posted the results for your perusal
>>> and information at www.ke7x.com.
>>>
>> Very interested findings - Fred has a graph of AGC action with AGC

THR=8
>> labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story :
>>
>> So I ask this group: is it possible to raise the AGC Threshold from s3
to
>> s6
>> or s9 by simply reducing the RF Gain control? Can anybody estimate what
>> settings of the RF Gain control would accomplish that?
>>
>> Barry N1EU
>>
>>
______________________________________________________________

______________________________________________________________
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Kok Chen

Re: An AGC story

On Dec 9, 2010, at 12/9 9:17 AM, [hidden email] wrote:

> But, since AGC works on every signal in the passband, if there are
> two signals - one S9 and the other S3 appearing at the same time,
> the S3 signal will disappear because the AGC is knocking down the
> S9 signal to an S3 level and thereby also reducing the S3 signal to
> the noise.

My impression from reading what has transpired is that some people are
more concerned that when the S9 signal is *not* there, that the S3
appears to be too loud?

We know that the S9+ signals have to be kept from saturating the A/D
converter (or even kept in check so the large signal doesn't do
naughty things to the IF amplifier and the SA612 second mixer -- I
don't know which of these three is the wimpiest in the chain). So
some AGC is neccessary.

Perhaps people will be happier if the AGC response is not as linear
(in the log-log scale) as the one in the K3 once you have past the AGC
threshold. I.e., perhaps people would care less if an S7 signal sound
as loud as an S9 signal, but they do want the S3 signal to sound less
loud as the S7 signal. A non-linear transfer function like that is
certainly "easy" to implement (as long as I don't have to be the one
to implement it :-), but will this make more people happy? Who knows?

Basically, this is what I am simple-mindedly visualizing: currently,
there are only two parameters to control a piecewise linear curve.

Imagine that there are three parameters, the current two, plus a
"upper threshold," after which the slope becomes "15" (i.e. flat at
S0 to THR, then constant "SLOPE" until "upper threshold" and then flat
from there until the front end starts to smoke),. You then smooth out
the piecewise linear curve using a pair of homotopy between those
three partitions. You will end up with (1) a smooth curve instead of
the piecewise linear one currently, and (2) a way to say "I care more
about distinguishing an S3 from an S9 signal than I do an S7 and S9
signal."

Notice that if a simple homotopy is applied to smooth the AGC transfer
function, and even if "upper threshold" is set to S7, you will still
hear a difference between S7 and S9 -- just much less than between S3
and S9. Also, if the AGC curve is no longer piecewise linear you will
still hear the S3 signal even if the lower threshold is set to an S3.

I still think the only way to satisfy "everybody" is if everyone would
homebrew their own rig, or sell an "open" commercial rig where you are
allowed to make any mods -- hardware, firmware, or software. See
first option :-) :-).

73
Chen, W7AY

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Andy Faber

Re: An AGC story

I have no doubt that AGC adjustments are largely a matter of personal
preference, and I congratulate Elecraft on making the K3 as adjustable as it
is without overwhelming us with so many variations that we'd go crazy trying
to figure it out.
As an example of individual adjustments, I used the K3 as my run radio in
CQWW CW from P49Y in 2009. Because I wanted help thinning out the pileup,
I found that setting the SLP to 1, but leaving the AGC on worked well, and
allowed me to ride the RF gain control to help distinguish signals while
still offering some AGC protection against very strong signals.
OTOH, in this years CQWW CW, where I was just doing some S&P DXing from my
home station, I set the SLP to 6, to allow me to turn the gain up higher to
detect weak signals while still having protection against very strong ones.
Using SLP 1 in that scenario with the RF gain all the way up was just too
close to not having AGC at all.
So I encourage everyone to experiment within the existing framework.
73, Andy ae6y
----- Original Message -----
From: "Kok Chen" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Cc: <[hidden email]>
Sent: Thursday, December 09, 2010 11:05 AM
Subject: Re: [Elecraft] An AGC story

> On Dec 9, 2010, at 12/9 9:17 AM, [hidden email] wrote:
>
>> But, since AGC works on every signal in the passband, if there are
>> two signals - one S9 and the other S3 appearing at the same time,
>> the S3 signal will disappear because the AGC is knocking down the
>> S9 signal to an S3 level and thereby also reducing the S3 signal to
>> the noise.
>
> My impression from reading what has transpired is that some people are
> more concerned that when the S9 signal is *not* there, that the S3
> appears to be too loud?
>
> We know that the S9+ signals have to be kept from saturating the A/D
> converter (or even kept in check so the large signal doesn't do
> naughty things to the IF amplifier and the SA612 second mixer -- I
> don't know which of these three is the wimpiest in the chain). So
> some AGC is neccessary.
>
> Perhaps people will be happier if the AGC response is not as linear
> (in the log-log scale) as the one in the K3 once you have past the AGC
> threshold. I.e., perhaps people would care less if an S7 signal sound
> as loud as an S9 signal, but they do want the S3 signal to sound less
> loud as the S7 signal. A non-linear transfer function like that is
> certainly "easy" to implement (as long as I don't have to be the one
> to implement it :-), but will this make more people happy? Who knows?
>
> Basically, this is what I am simple-mindedly visualizing: currently,
> there are only two parameters to control a piecewise linear curve.
>
> Imagine that there are three parameters, the current two, plus a
> "upper threshold," after which the slope becomes "15" (i.e. flat at
> S0 to THR, then constant "SLOPE" until "upper threshold" and then flat
> from there until the front end starts to smoke),. You then smooth out
> the piecewise linear curve using a pair of homotopy between those
> three partitions. You will end up with (1) a smooth curve instead of
> the piecewise linear one currently, and (2) a way to say "I care more
> about distinguishing an S3 from an S9 signal than I do an S7 and S9
> signal."
>
> Notice that if a simple homotopy is applied to smooth the AGC transfer
> function, and even if "upper threshold" is set to S7, you will still
> hear a difference between S7 and S9 -- just much less than between S3
> and S9. Also, if the AGC curve is no longer piecewise linear you will
> still hear the S3 signal even if the lower threshold is set to an S3.
>
> I still think the only way to satisfy "everybody" is if everyone would
> homebrew their own rig, or sell an "open" commercial rig where you are
> allowed to make any mods -- hardware, firmware, or software. See
> first option :-) :-).
>
> 73
> Chen, W7AY
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

David Gilbert

Re: An AGC story

That is why it would be highly desirable to be able to quickly change
AGC settings on the fly, especially when you consider the additional
effect that different band noise has on the optimum AGC profile. I can
understand Elecraft's reluctance to let users mess with the DSP code via
macros, but I don't understand why it should not be possible to use
macros to select from a few different AGC settings that have been preset
using the CONFIG menu. It doesn't seem rational to me to build all that
versatility into the AGC system so that it can be tailored to deal with
all sorts of operating conditions ... different levels and types of band
noise, different degrees of QRM, different levels of signal strengths,
etc ... and then force you to choose only one setting for everything,
especially during a contest.

73,
Dave AB7E

On 12/9/2010 12:20 PM, Andrew Faber wrote:

> I have no doubt that AGC adjustments are largely a matter of personal
> preference, and I congratulate Elecraft on making the K3 as adjustable as it
> is without overwhelming us with so many variations that we'd go crazy trying
> to figure it out.
> As an example of individual adjustments, I used the K3 as my run radio in
> CQWW CW from P49Y in 2009. Because I wanted help thinning out the pileup,
> I found that setting the SLP to 1, but leaving the AGC on worked well, and
> allowed me to ride the RF gain control to help distinguish signals while
> still offering some AGC protection against very strong signals.
> OTOH, in this years CQWW CW, where I was just doing some S&P DXing from my
> home station, I set the SLP to 6, to allow me to turn the gain up higher to
> detect weak signals while still having protection against very strong ones.
> Using SLP 1 in that scenario with the RF gain all the way up was just too
> close to not having AGC at all.
> So I encourage everyone to experiment within the existing framework.
> 73, Andy ae6y

Don Wilhelm-4

Re: An AGC story

Dave,

You can *effectively* increase the AGC threshold by 10 dB very quickly -
just turn on the attenuator.
Actually, that is more effective than reducing the RF Gain because it
happens at the receiver input rather than at the IF.
Yes, you can turn the attenuator of the K3 on whether or not the Preamp
is on.
And, if you have the S-meter set for "abs" (absolute) mode, it will not
change with the attenuator or preamp.

If you have signals high enough to produce greater than an S-3 level,
you will still hear them when you turn the attenuator on, and the
dynamic range of the K3 is retained.

73,
Don W3FPR

On 12/9/2010 3:02 PM, David Gilbert wrote:

>
> That is why it would be highly desirable to be able to quickly change
> AGC settings on the fly, especially when you consider the additional
> effect that different band noise has on the optimum AGC profile. I can
> understand Elecraft's reluctance to let users mess with the DSP code via
> macros, but I don't understand why it should not be possible to use
> macros to select from a few different AGC settings that have been preset
> using the CONFIG menu. It doesn't seem rational to me to build all that
> versatility into the AGC system so that it can be tailored to deal with
> all sorts of operating conditions ... different levels and types of band
> noise, different degrees of QRM, different levels of signal strengths,
> etc ... and then force you to choose only one setting for everything,
> especially during a contest.
>

Joe Subich, W4TV-4

Re: An AGC story

In reply to this post by Kok Chen

Chen,

> Imagine that there are three parameters, the current two, plus a
> "upper threshold," after which the slope becomes "15" (i.e. flat at
> S0 to THR, then constant "SLOPE" until "upper threshold" and then flat
> from there until the front end starts to smoke),.

The AGC is already a three piece curve. Below the AGC threshold (-117
to -99 dBm depending on THR) the audio:RF response is 1:1. Above the
threshold the audio:RF ratio varies between 0.4 dB/dB to 0.05 dB/dB
(according to K8OZA's measurements) until the HAGC activates between -43
and -48 dBm at which time the output becomes flat (no further increase).

What this discussion appears to be asking for is the option to raise
the level of first inflection point (AGC threshold) from approximately
-99 dBm with THR=08 to somewhere in the mid -70 dBm range without using
the attenuator and losing the weak signals. That is, nobody wants to
give up the ability to receive a -128 dBm signal by using a 10 or 20 dB
of attenuation when the receiver is easily capable of detecting a -130
dBm signal without use of a preamplifier but they do want reasonable
"level cues" to use in separating signals close to the same frequency.

What is needed is to broaden out the steps in THR from as little as 1
dB per step to something like a uniform 6 dB per step or adding more
steps (e.g., 16 choices at 3 dB/step so that the threshold can be set
over a -117 to -70 dBm range rather than the current limited -117 to -99
dBm range (K8OZA measurements).

Since HAGC does not activate until the RF input reaches -48 to -43 dBm,
one must assume that the IF amplifier, 2nd Mixer and ADC are capable
of functioning properly well beyond the levels generated at -70 dBm
input and raising the threshold even if it means using a flatter slope
would not cause serious performance issues.

73,

... Joe, W4TV

On 12/9/2010 2:05 PM, Kok Chen wrote:

Sverre Holm (LA3ZA)

Re: An AGC story

In reply to this post by Don Wilhelm-4

This is exactly what I found useful during the CQ WW CW contest. I did some 500+ QSOs and found that it is easier to listen to the K3 with the Attenuator on in the 20 m band. In this band this is something I rarely do with the K2. This discussion on AGC threshold has perhaps told me the reason why this is so.

Don Wilhelm-4 wrote

You can *effectively* increase the AGC threshold by 10 dB very quickly -
just turn on the attenuator.

Sverre, LA3ZA

K2 #2198, K3 #3391,
LA3ZA Blog: http://la3za.blogspot.com,
LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html

David Gilbert

Re: An AGC story

In reply to this post by Don Wilhelm-4

OK, but that still doesn't address decay or slope ... parameters I might
want to quickly change dependent upon the amount and type of band noise
(such as when changing to the low bands or when thunderstorms are
active) or the number (not only the level) of signals (pileup or QRM).

I still say a few re-callable combinations of AGC settings would make
sense, even if they had to be initially configured only through the
CONFIG menu.

73,
Dave AB7E

On 12/9/2010 1:17 PM, Don Wilhelm wrote:

> Dave,
>
> You can *effectively* increase the AGC threshold by 10 dB very quickly
> - just turn on the attenuator.
> Actually, that is more effective than reducing the RF Gain because it
> happens at the receiver input rather than at the IF.
> Yes, you can turn the attenuator of the K3 on whether or not the
> Preamp is on.
> And, if you have the S-meter set for "abs" (absolute) mode, it will
> not change with the attenuator or preamp.
>
> If you have signals high enough to produce greater than an S-3 level,
> you will still hear them when you turn the attenuator on, and the
> dynamic range of the K3 is retained.
>
> 73,
> Don W3FPR
>
> On 12/9/2010 3:02 PM, David Gilbert wrote:
>>
>> That is why it would be highly desirable to be able to quickly change
>> AGC settings on the fly, especially when you consider the additional
>> effect that different band noise has on the optimum AGC profile. I can
>> understand Elecraft's reluctance to let users mess with the DSP code via
>> macros, but I don't understand why it should not be possible to use
>> macros to select from a few different AGC settings that have been preset
>> using the CONFIG menu. It doesn't seem rational to me to build all that
>> versatility into the AGC system so that it can be tailored to deal with
>> all sorts of operating conditions ... different levels and types of band
>> noise, different degrees of QRM, different levels of signal strengths,
>> etc ... and then force you to choose only one setting for everything,
>> especially during a contest.
>>
>

k5oai

Re: An AGC story

check out K3_EZ
http://home.roadrunner.com/~n2bc/SW.htm
then connect and check out the AGC Setup page

GB & 73
K5OAI
Sam Morgan

On 12/9/2010 8:49 PM, David Gilbert wrote:

>
> OK, but that still doesn't address decay or slope ... parameters I might
> want to quickly change dependent upon the amount and type of band noise
> (such as when changing to the low bands or when thunderstorms are
> active) or the number (not only the level) of signals (pileup or QRM).
>
> I still say a few re-callable combinations of AGC settings would make
> sense, even if they had to be initially configured only through the
> CONFIG menu.
>
> 73,
> Dave AB7E

David Gilbert

Re: An AGC story

Nice program, but it doesn't run with LP-Bridge if I want to have more
than one application (N1MM, CW Skimmer, K3_EZ, etc) interfacing with my
K3. It is fine for simplifying the changing of AGC settings, but not on
the fly during a contest.

Dave AB7E

On 12/9/2010 8:18 PM, Sam Morgan wrote:

> check out K3_EZ
> http://home.roadrunner.com/~n2bc/SW.htm
> then connect and check out the AGC Setup page
>
> GB& 73
> K5OAI
> Sam Morgan
>
> On 12/9/2010 8:49 PM, David Gilbert wrote:
>> OK, but that still doesn't address decay or slope ... parameters I might
>> want to quickly change dependent upon the amount and type of band noise
>> (such as when changing to the low bands or when thunderstorms are
>> active) or the number (not only the level) of signals (pileup or QRM).
>>
>> I still say a few re-callable combinations of AGC settings would make
>> sense, even if they had to be initially configured only through the
>> CONFIG menu.
>>
>> 73,
>> Dave AB7E
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gm3sek

Re: An AGC story

In reply to this post by David Gilbert

David Gilbert wrote:

>
>OK, but that still doesn't address decay or slope ... parameters I
>might want to quickly change dependent upon the amount and type of band
>noise (such as when changing to the low bands or when thunderstorms are
>active) or the number (not only the level) of signals (pileup or QRM).
>
>I still say a few re-callable combinations of AGC settings would make
>sense, even if they had to be initially configured only through the
>CONFIG menu.
>

It might be more helpful to store the AGC threshold and slope per-band.

The underlying problem is that many people will see a 30-40dB variation
in antenna noise levels between 30MHz and 1.8MHz, and the K3 has only
limited facilities to pre-set its front end gain (the one-step 10dB
attenuator, the +12dB preamp and the manual IF gain control). After
that, it's all down to the AGC.

--

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek
______________________________________________________________
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html

Barry N1EU

Re: An AGC story

In reply to this post by David Gilbert

David Gilbert wrote

Nice program, but it doesn't run with LP-Bridge if I want to have more
than one application (N1MM, CW Skimmer, K3_EZ, etc) interfacing with my
K3. It is fine for simplifying the changing of AGC settings, but not on
the fly during a contest.

I strongly agree. There's a great need for some simple utilities for the K3 that will run with LP-Bridge or other CAT port sharing schemes: AGC/EQ management, expanded rig display, subrx control (avoid BSET), etc

Barry N1EU

N8LP

Re: An AGC story

In reply to this post by Cady, Fred

I have been talking with Dick Dievendorf about changes to the K3
Utility and LP-Bridge to allow most of the utility functionality to work
(not including firmware revisions, however). This should benefit other
utilities as well. The problem is finding time for changes and testing.

Larry N8LP

On 12/10/2010 12:00 PM, [hidden email] wrote:

> Date: Fri, 10 Dec 2010 03:39:04 -0800 (PST)
> From: Barry N1EU<[hidden email]>
> Subject: Re: [Elecraft] An AGC story
> To:[hidden email]
> Message-ID:<[hidden email]>
> Content-Type: text/plain; charset=us-ascii
>
>
>
> David Gilbert wrote:
>> >
>> > Nice program, but it doesn't run with LP-Bridge if I want to have more
>> > than one application (N1MM, CW Skimmer, K3_EZ, etc) interfacing with my
>> > K3. It is fine for simplifying the changing of AGC settings, but not on
>> > the fly during a contest.
>> >
> I strongly agree. There's a great need for some simple utilities for the K3
> that will run with LP-Bridge or other CAT port sharing schemes: AGC/EQ
> management, expanded rig display, subrx control (avoid BSET), etc
>
> Barry N1EU