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Attenuator and RF Gain Settings

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juergen piezo

Attenuator and RF Gain Settings

Hi Lance

This issue is a real problem for me. If I turn the AGC off I need too use the noise blanker. This ruins the K3's strong signal handling performance. Normally I dont need to use the noise blanker. However with the AGC off, electric fence pulses are loud as hell because the pulse stretching blanker is not on with the AGC off.

This problem with the K3's producing noise with AGC on is real problem. On my 40 meter 4 square I basically have a very low noise floor S1 -S2. With AGC on I am getting QRN that the K3 AGC makes thats not really at the level that the K3 is reporting. Yes there is QRN there, but its residual with occasional pops, not the S5 and S7 QRN crashes that the AGC produces. This is not a S meter calibration issue either. Like you my QRN level jumps up mysteriously. With the AGC is off this QRN is not there. I have the threshold set at 2. Even with the ATT on this QRN is being made much more apparent with the AGC on. I hope Elecraft has a fix for this because the K3 is unusable for me in its current form on the low bands.

In the 160m CW contest, because of the QRN I had too use my TS850 and lowly IC735 which seemed too cope much better in mild QRN conditions. The K3's AGC under these conditions was making the band sound like I needed to disconnect the antenna very soon!

John

This is a very interesting thread. I am seeing a similar RF gain/AGC issue on
my K3 (I posted a description of this effect on 1/31). While I have also
defaulted to presetting the AFG and use the RF gain to control receiver
performance, I have noticed issues with the AGC on the K3 that make it
behave differently than other radios that I have tried. The K3 has both
hardware and DSP/firmware AGC.

Strong signals (over S9) cause the AGC to behave normally but weak signals
(DSP/firmware) behave oddly with an apparent, and I say apparent, noise
issue. Audio quality of weak signals with the AGC on also seems to be
slightly compromised as compared to operation with the AGC off.

Perhaps weak signal performance of the K3 with AGC on needs some
DSP/firmware modification. In the meantime, I am using the rig in a similar
fashion as Barry and other have described.

Lance, NR7N

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Don Wilhelm-4

Re: Attenuator and RF Gain Settings

John,

If you have electric fence impulse noise, an AGC Threshold setting of
002 is too low IMHO. Try setting it higher, say at 008 and see what
happens. If the noise is still a problem (with AGC ON), then try
reducing the slope to 004 or even 002 - with the reduced slope, strong
signals will sound louder than weak ones in your ears, which I consider
a good thing - ragchewers looking for only 'armchair copy' may differ
and want to use a higher slope so all signals have about the same audio
level regardless of signal strength.

73,
Don W3FPR

juergen wrote:

> Hi Lance
>
> This issue is a real problem for me. If I turn the AGC off I need too use the noise blanker. This ruins the K3's strong signal handling performance. Normally I dont need to use the noise blanker. However with the AGC off, electric fence pulses are loud as hell because the pulse stretching blanker is not on with the AGC off.
>
> This problem with the K3's producing noise with AGC on is real problem. On my 40 meter 4 square I basically have a very low noise floor S1 -S2. With AGC on I am getting QRN that the K3 AGC makes thats not really at the level that the K3 is reporting. Yes there is QRN there, but its residual with occasional pops, not the S5 and S7 QRN crashes that the AGC produces. This is not a S meter calibration issue either. Like you my QRN level jumps up mysteriously. With the AGC is off this QRN is not there. I have the threshold set at 2. Even with the ATT on this QRN is being made much more apparent with the AGC on. I hope Elecraft has a fix for this because the K3 is unusable for me in its current form on the low bands.
>
> In the 160m CW contest, because of the QRN I had too use my TS850 and lowly IC735 which seemed too cope much better in mild QRN conditions. The K3's AGC under these conditions was making the band sound like I needed to disconnect the antenna very soon!
>
>
> John
>
>

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Don Wilhelm-4

Re: Attenuator and RF Gain Settings

In reply to this post by juergen piezo

For ALL - a further explanation! The K3 does not make noise louder!
BUT one *can* make that happen with incorrect settings.

The AGC Threshold must be set above the level of the noise. If that is
not done, the AGC will activate on the noise and reduce the gain of the
receiver. The result is that signals which *should* stand out above the
noise will be buried closer to the noise because their level has been
reduced by the AGC action.
Reducing the RF Gain will normally accomplish the same thing.
Since all K3s are not at the same location with the same atmospheric
noise level, the correct settings for one may not be right for another.
It all depends on the local noise, the atmospheric noise coming into
your antenna.

I am not certain how a person can say that the atmospheric noise on his
antenna is S-2 to S-3, but the K3 S-meter reads the noise as S-5 to
S-7. I just don't understand that - what is the "standard of
comparison"? The noise is whatever it is, and the level indicated on
any one receiver will depend on the sensitivity of the receiver as well
as its S-meter response. A receiver with a better MDS *should* receive
that noise at a higher level than one with a lesser MDS. The answer is
to either add attenuation until the noise is reduced (preamp off,
Attenuator on, RF Gain backed off), or change the onset of AGC so the
noise does not trigger it - or both. Signals that are greater than the
noise will still be present and can be copied.

73,
Don W3FPR

juergen wrote:
> This problem with the K3's producing noise with AGC on is real problem. On my 40 meter 4 square I basically have a very low noise floor S1 -S2. With AGC on I am getting QRN that the K3 AGC makes thats not really at the level that the K3 is reporting. Yes there is QRN there, but its residual with occasional pops, not the S5 and S7 QRN crashes that the AGC produces. This is not a S meter calibration issue either. Like you my QRN level jumps up mysteriously. With the AGC is off this QRN is not there. I have the threshold set at 2. Even with the ATT on this QRN is being made much more apparent with the AGC on. I hope Elecraft has a fix for this because the K3 is unusable for me in its current form on the low bands.
>
>
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Don Wilhelm-4

Re: Attenuator and RF Gain Settings

I just thought of something that might help those confused by the AGC
Threshold setting.
One other way to look at the required AGC Threshold level is to think of
it as an S-meter level
If your noise is S-1 or lower (on the K3's S-meter), you can set the
Threshold to 002 or higher and all may be well
OTOH, if you have an S-7 noise level indicated, the AGC Threshold should
be set to 008 or higher.

This is not an exact science number - the AGC Threshold menu parameter
values are not tied to the S-meter, but hopefully the relative scale can
give you an indication of which way to move the setting to avoid
activating the AGC on the ambient noise coming in on your feedline.

As I have said before I believe the default setting of 005 is even too
low - mine normally is set at 008 even though I have a relatively quiet
location.

73,
Don W3FPR

Don Wilhelm wrote:

> For ALL - a further explanation! The K3 does not make noise louder!
> BUT one *can* make that happen with incorrect settings.
>
> The AGC Threshold must be set above the level of the noise. If that is
> not done, the AGC will activate on the noise and reduce the gain of the
> receiver. The result is that signals which *should* stand out above the
> noise will be buried closer to the noise because their level has been
> reduced by the AGC action.
> Reducing the RF Gain will normally accomplish the same thing.
> Since all K3s are not at the same location with the same atmospheric
> noise level, the correct settings for one may not be right for another.
> It all depends on the local noise, the atmospheric noise coming into
> your antenna.
>
> I am not certain how a person can say that the atmospheric noise on his
> antenna is S-2 to S-3, but the K3 S-meter reads the noise as S-5 to
> S-7. I just don't understand that - what is the "standard of
> comparison"? The noise is whatever it is, and the level indicated on
> any one receiver will depend on the sensitivity of the receiver as well
> as its S-meter response. A receiver with a better MDS *should* receive
> that noise at a higher level than one with a lesser MDS. The answer is
> to either add attenuation until the noise is reduced (preamp off,
> Attenuator on, RF Gain backed off), or change the onset of AGC so the
> noise does not trigger it - or both. Signals that are greater than the
> noise will still be present and can be copied.
>
> 73,
> Don W3FPR
>
> juergen wrote:
>
>> This problem with the K3's producing noise with AGC on is real problem. On my 40 meter 4 square I basically have a very low noise floor S1 -S2. With AGC on I am getting QRN that the K3 AGC makes thats not really at the level that the K3 is reporting. Yes there is QRN there, but its residual with occasional pops, not the S5 and S7 QRN crashes that the AGC produces. This is not a S meter calibration issue either. Like you my QRN level jumps up mysteriously. With the AGC is off this QRN is not there. I have the threshold set at 2. Even with the ATT on this QRN is being made much more apparent with the AGC on. I hope Elecraft has a fix for this because the K3 is unusable for me in its current form on the low bands.
>>
>>
>>
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ab2tc

Re: Attenuator and RF Gain Settings

Hi,

I wish I could set it higher than 008. I am also in a relatively quiet location but on 20m with an AGC threshold of 008 my atmospheric noise is normally above the AGC threshold. So when I want comfortable listening I back off the RF gain until the S-meter shows about S4 or so. Not a big problem, but I would prefer that the AGC threshold could go higher. Having it stored per-band, too, would be really, really nice and it makes sense.

Knut - AQB2TC

Don Wilhelm-4 wrote

I just thought of something that might help those confused by the AGC
Threshold setting.
One other way to look at the required AGC Threshold level is to think of
it as an S-meter level
If your noise is S-1 or lower (on the K3's S-meter), you can set the
Threshold to 002 or higher and all may be well
OTOH, if you have an S-7 noise level indicated, the AGC Threshold should
be set to 008 or higher.
<snip>

Julian, G4ILO

Re: Attenuator and RF Gain Settings

ab2tc wrote

I wish I could set it higher than 008.

So do I.

Julian, G4ILO. K2 #392 K3 #222 KX3 #110
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

Jim Brown-10

Re: Attenuator and RF Gain Settings

In reply to this post by Don Wilhelm-4

On Tue, 02 Feb 2010 16:34:50 -0500, Don Wilhelm wrote:

>BUT one *can* make that happen with incorrect settings.

YES! Don has given us a LOT of great advice in his two recent
posts in this thread. Let me emphasize something that I'm sure he
understands, but didn't make quite it clear if you didn't read
between his lines.

NOISE IS PART OF THE SIGNAL THAT IS DRIVING THE AGC. IT IS ALSO
PART OF THE SIGNAL THAT IS GENERATING INTERMOD, BOTH AT RF AND AT
AUDIO. IT IS PART OF WHAT THE IF SELECTIVITY MUST REJECT, JUST
LIKE ANOTHER STATION!

CAPS ADDED FOR EMPHASIS.

If the NOISE overloads the signal chain, the resulting distortion
obscures the signal. It is not enough to keep the signal chain
below overload on signal. We must also keep it out of overload by
noise pulses. That's not easy, because much of the noise at the
antenna terminal is impulsive in nature -- certainly static and
stuff like fences.

Bear this in mind when setting ATT, PRE, RF gain, and AGC
parameters.

73,

Jim K9YC

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K1LI

Re: Attenuator and RF Gain Settings

In reply to this post by Don Wilhelm-4

Wow, Don, the effect of setting the AGC THR is dramatic!

I live in a very rural location that seems relatively free of man-made
noise. With antenna connected, the K3 S-meter shows about S-5 background
noise. (S-0 with no antenna!)

Surprising to me, turning *down* the AGC THR to 002 (was set to 008) really
quieted things down and made signals "pop" out of the noise the way you
describe. (Note: NF and NB are OFF) I could hear the background noise level
rise monotonically as I increased the THR setting and fall as I decreased
it.

With seven AGC variables to adjust -- DCY, HLD, PLS, SLP, THR, -F and -S --
setting AGC up for a given operating scenario in a given location seems like
a very complex topic. Is there any way this could be reduced to a tutorial
for the K3 Wiki (like K3NA's entry at
http://www.zerobeat.net/mediawiki/index.php/K3_Receiver_Gain_Configurations,
which addresses the "no AGC" case)?

This might create a run on N-GENs...

--
73 -- Brian -- K1LI

On Tue, Feb 2, 2010 at 4:50 PM, Don Wilhelm <[hidden email]> wrote:

> I just thought of something that might help those confused by the AGC
> Threshold setting. One other way to look at the required AGC Threshold level
> is to think of it as an S-meter level If your noise is S-1 or lower (on the
> K3's S-meter), you can set the Threshold to 002 or higher and all may be
> well OTOH, if you have an S-7 noise level indicated, the AGC Threshold
> should be set to 008 or higher.
>
> This is not an exact science number - the AGC Threshold menu parameter
> values are not tied to the S-meter, but hopefully the relative scale can
> give you an indication of which way to move the setting to avoid activating
> the AGC on the ambient noise coming in on your feedline.
>
> As I have said before I believe the default setting of 005 is even too low
> - mine normally is set at 008 even though I have a relatively quiet
> location.
>
> 73,
> Don W3FPR
>

Guy, K2AV

Re: Attenuator and RF Gain Settings

In reply to this post by juergen piezo

In the K3 there are *TWO* kinds of noise blanking. One is digital and
runs inside the firmware program. The other is the same hardware IF
blanking that has been in use in analog radios for over 50 years. They
do not work at all alike.

The hardware blanking has advantages on some noise and was retained as
one of the blanking options (marked IF). Hardware blanking, as it
always has, will create extra noise from strong signals, because it is
modulating the spectrum with a square transition of IF gain from on to
off. The artifacts are just a matter of physics in anyone's radio.
Hardware blanking is hardware blanking.

The digital "blanking" (dSP in the NB menu selection) uses algorithmic
methodology and does not produce these artifacts. It is a better
phrase to call the dsp version "noise cancellation".

Press and hold NB to bring up the NB level menu and turn IF OFF with
the VFO B knob. Luckily, at my QTH I have not found a point where I
need the hardware blanking. Whatever causes my 160m S9 (50uV in 50
ohms) daytime buzz (not found in two years of searching) is reduced to
S6 (6uV) by the dsp blanking, but only to s7/s8 (12 to 25 uV) by
hardware blanking. When the buzz is gone, ambient 160m noise at SSB
bandwidths is S6.

Also be sure to use as little of the ATT-nothing-PRE gain range as you
can, as this ramps up the pulses as well as the wanted signal.
Keeping this at a minimum allows me to use the dsp blanking.

73, Guy

PS, I have my S meter set to ABS (absolute) and have done RF gain
calibration, and so my S meter CAN be read in uV when AGC is on.

On Tue, Feb 2, 2010 at 3:40 PM, juergen <[hidden email]> wrote:
> Hi Lance
>
> This issue is a real problem for me. If I turn the AGC off I need too use the noise blanker. This ruins the K3's strong signal handling performance. Normally I dont need to use the noise blanker. However with the AGC off, electric fence pulses are loud as hell because the pulse stretching blanker is not on with the AGC off.
>
> This problem with the K3's producing noise with AGC on is real problem.
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KK7P

Re: Attenuator and RF Gain Settings

In addition to the IF and DSP noise blankers, the K3 incorporates a
third feature to help deal with impulse noise.

One of the AGC parameters is CONFIG: AGC PLS.

"nor" is used to activate a fast-reovery AGC algorithm if the signal
that activated the AGC is above a certain dynamic threshold and lasts
for less than a specific time.

"OFF" allows the AGC to be "pumped" by pulse-type noise.

Like any system that deals with suppressing pulse noise, the overall
receiver gain is being quickly modified, so there may be IMD or other
effects.

73,

Lyle KK7P
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Don Wilhelm-4

Re: Attenuator and RF Gain Settings

In reply to this post by K1LI

Brian,

That is an illusion - yes the K3 gets more quiet (on noise) if the AGC
Threshold is reduced.
BUT what that indicates is that the AGC is being activated by the noise
and the K3 is reducing the gain due to AGC action.
The lowest AGC Threshold that is usable for any given level of
atmospheric noise is the threshold setting just higher than the setting
which begins to reduce the noise. In other words, listen to a spot on
the band where there are no signals, then start at the highest Threshold
setting of 008.
Reduce the value of the AGC Threshold until you sense that the noise
level starts to go down - then move the Threshold up to the next level.

That setting will produce the most usable sensitivity for that band,
that antenna, and at that particular point in time (atmospheric noise
levels do change with time). If the resulting noise level is
bothersome, then take other steps to reduce that response - Preamp off,
ATT ON, and reduce the RF Gain (in that order) until you can just barely
hear the noise. That will result in the most sensitive setting for the
receiver.
Remember (as Jim Brown just posted) - that atmospheric noise is just
another 'signal' to the receiver that is to be amplified (it is coming
in on the antenna port). One must condition the receiver to place that
noise level at (or just above) your threshold of perception to reduce
your fatigue level when listening to any band. That is what the preamp,
attenuator, and RF Gain controls are for.

After a bit of experimenting, you may come to the point where you have
achieved a compromise set of AGC Threshold and Slope setting that work
well in all but the most demanding situations. Leave them set at that
point and control the receiver response with the normal controls of
preamp, ATT, and RF Gain. For those digging for signals beneath the
noise level (yes, some ops have very good ears for that), they will have
to suffer with hearing some of the noise as well - just how much is an
individual decision.

Again, as Jim Brown pointed out - noise arriving from the antenna is
just another signal source - some signals will be above that noise level
and others will be below it. Normally we can only copy signals that are
above the noise level, so why do some insist on setting "all controls to
the right" and having the receiver amplify the noise as well as the
signals - it is all in the quantity called "(signal + noise) to noise
ratio".

The only way to further reduce noise is to use noise reduction
techniques which search through the signal plus noise to find something
that appears to be coherent and amplify it. That is what the K3 NR
algorithms do. How well it works depends on the type of noise present
at the time, and the K3 offers several settings to handle the differing
situations - do expect distortion with the more aggressive settings, but
if they are able to dig a signal out of the noise for us, perhaps we can
put up with the distortion to complete the contact. This is for use in
extreme situations, and not for normal use when we want more casual copy.

73,
Don W3FPR

Brian Machesney wrote:

> Wow, Don, the effect of setting the AGC THR is dramatic!
>
> I live in a very rural location that seems relatively free of man-made
> noise. With antenna connected, the K3 S-meter shows about S-5 background
> noise. (S-0 with no antenna!)
>
> Surprising to me, turning *down* the AGC THR to 002 (was set to 008) really
> quieted things down and made signals "pop" out of the noise the way you
> describe. (Note: NF and NB are OFF) I could hear the background noise level
> rise monotonically as I increased the THR setting and fall as I decreased
> it.
>
> With seven AGC variables to adjust -- DCY, HLD, PLS, SLP, THR, -F and -S --
> setting AGC up for a given operating scenario in a given location seems like
> a very complex topic. Is there any way this could be reduced to a tutorial
> for the K3 Wiki (like K3NA's entry at
> http://www.zerobeat.net/mediawiki/index.php/K3_Receiver_Gain_Configurations,
> which addresses the "no AGC" case)?
>
> This might create a run on N-GENs...
>
>
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.733 / Virus Database: 271.1.1/2663 - Release Date: 02/02/10 02:35:00
>
>

Don Wilhelm-4

Re: Attenuator and RF Gain Settings

For those who can gather information from graphs, take a look at the AGC
behavior Jack Smith has plotted. The information is at
http://www.cliftonlaboratories.com/elecraft_k3_agc_and_s-meter.htm#AGC_SLP_and_AGC_THR.

73,
Don W3FPR

Don Wilhelm wrote:

> Brian,
>
> That is an illusion - yes the K3 gets more quiet (on noise) if the AGC
> Threshold is reduced.
> BUT what that indicates is that the AGC is being activated by the noise
> and the K3 is reducing the gain due to AGC action.
> The lowest AGC Threshold that is usable for any given level of
> atmospheric noise is the threshold setting just higher than the setting
> which begins to reduce the noise. In other words, listen to a spot on
> the band where there are no signals, then start at the highest Threshold
> setting of 008.
> Reduce the value of the AGC Threshold until you sense that the noise
> level starts to go down - then move the Threshold up to the next level.
>
> That setting will produce the most usable sensitivity for that band,
> that antenna, and at that particular point in time (atmospheric noise
> levels do change with time). If the resulting noise level is
> bothersome, then take other steps to reduce that response - Preamp off,
> ATT ON, and reduce the RF Gain (in that order) until you can just barely
> hear the noise. That will result in the most sensitive setting for the
> receiver.
> Remember (as Jim Brown just posted) - that atmospheric noise is just
> another 'signal' to the receiver that is to be amplified (it is coming
> in on the antenna port). One must condition the receiver to place that
> noise level at (or just above) your threshold of perception to reduce
> your fatigue level when listening to any band. That is what the preamp,
> attenuator, and RF Gain controls are for.
>
> After a bit of experimenting, you may come to the point where you have
> achieved a compromise set of AGC Threshold and Slope setting that work
> well in all but the most demanding situations. Leave them set at that
> point and control the receiver response with the normal controls of
> preamp, ATT, and RF Gain. For those digging for signals beneath the
> noise level (yes, some ops have very good ears for that), they will have
> to suffer with hearing some of the noise as well - just how much is an
> individual decision.
>
> Again, as Jim Brown pointed out - noise arriving from the antenna is
> just another signal source - some signals will be above that noise level
> and others will be below it. Normally we can only copy signals that are
> above the noise level, so why do some insist on setting "all controls to
> the right" and having the receiver amplify the noise as well as the
> signals - it is all in the quantity called "(signal + noise) to noise
> ratio".
>
> The only way to further reduce noise is to use noise reduction
> techniques which search through the signal plus noise to find something
> that appears to be coherent and amplify it. That is what the K3 NR
> algorithms do. How well it works depends on the type of noise present
> at the time, and the K3 offers several settings to handle the differing
> situations - do expect distortion with the more aggressive settings, but
> if they are able to dig a signal out of the noise for us, perhaps we can
> put up with the distortion to complete the contact. This is for use in
> extreme situations, and not for normal use when we want more casual copy.
>
> 73,
> Don W3FPR
>
>

ab2tc

Re: Attenuator and RF Gain Settings

In reply to this post by Julian, G4ILO

Hi Julian,

I have posted and E-mailed about this at least a dozen times to no
avail. I am convinced that if Elecraft could do this, almost all of the
"noisy and hissy" receiver complaints would go away overnight. So I
don't understand why they aren't listening to their users on this. This
is just about my only complaint (except the 3.9 and and 7.8kHz audio
spurs) about the K3.

Knut - AB2TC

Julian, G4ILO [via Elecraft] wrote:

>
> ab2tc wrote:
> I wish I could set it higher than 008.
>
> So do I.
> Julian, G4ILO. K2 #392 K3 #222.
> * G4ILO's Shack - http://www.g4ilo.com
> * KComm - http://www.g4ilo.com/kcomm.html
> * KTune - http://www.g4ilo.com/ktune.html
>
>
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Jim Dunstan

Re: Attenuator and RF Gain Settings

In reply to this post by Don Wilhelm-4

At 07:10 PM 2/2/2010 -0500, you wrote:

Hi,

I am not an Elecraft owner ... yet ... However I have built (homebrewed)
many receivers over the years ... and building a good AGC system is one of
the hardest parts (biggest challenge in modern parlance). One of the
things I learned after many years is how to make the AGC sensitive to
noise. Most of the receivers I built and commercial ones I have used
basically relate the AGC level exclusively to received signal. However in
designing the AGC detector time constants I found it very useful to have
receiver gain controlled by noise level to some degree. As background
noise goes up ... receiver gain goes down to a degree ... and as the
background gets quieter gain should go up a little. I never did get it
just right ... and the general front end attenuator and RF gain control
always got used a lot hi hi.

I find the topic very interesting .... and I find it very encouraging the
effort put into AGC design in the K3.

Jim,
VE3CI

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Bill W4ZV

Re: Attenuator and RF Gain Settings

In reply to this post by juergen piezo

juergen piezo wrote

In the 160m CW contest, because of the QRN I had too use my TS850 and lowly IC735 which seemed too cope much better in mild QRN conditions. The K3's AGC under these conditions was making the band sound like I needed to disconnect the antenna very soon!

You must be kidding! I operated 30 hours in the CQ 160 and never turned my AGC off even once. I was in the middle of the major storm cell that moved across the southeast with QRN SW of me Friday night and NE of me Saturday night. Somehow I still managed to make 1542 QSOs in 58 State/Prov and 68 countries with a total Score of 829,332 (probably 5th overall behind 3 stations in Maine and one on the Chesapeake shore).

http://lists.contesting.com/pipermail/3830/2010-February/190837.html

I really don't understand your comments. Would you mind sharing your callsign and results in the CQ 160 so we know you are not simply a troll?

73, Bill W4ZV

Joe Subich, W4TV-4

Re: Attenuator and RF Gain Settings

In reply to this post by ab2tc

> I wish I could set it higher than 008. I am also in a
> relatively quiet location but on 20m with an AGC threshold of
> 008 my atmospheric noise is normally above the AGC threshold.

If one looks at Jack Smith's graphs, the K2 threshold (between
-80 and -90 dBm) would be about 11 or 12 for the K3 and the
slope is about 5 or 6. Jack's measurements show that even at
8, the K3's AGC threshold (onset of AGC) is down around -100dBm.

Sherwood shows the K3's AGC threshold at 2.1 uV vs. 10 uV (no
preamp) for the K2 and .6uV vs. 1.7 uV with the preamp. I
find it interesting that Sherwood's measurements of the
FT-1000D (6 uV) and FT-1000MP MK V (3 uV) also show higher
AGC thresholds with the preamplifier on.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of ab2tc
> Sent: Tuesday, February 02, 2010 5:08 PM
> To: [hidden email]
> Subject: Re: [Elecraft] Attenuator and RF Gain Settings
>
>
>
> Hi,
>
> I wish I could set it higher than 008. I am also in a
> relatively quiet location but on 20m with an AGC threshold of
> 008 my atmospheric noise is normally above the AGC threshold.
> So when I want comfortable listening I back off the RF gain
> until the S-meter shows about S4 or so. Not a big problem,
> but I would prefer that the AGC threshold could go higher.
> Having it stored per-band, too, would be really, really nice
> and it makes sense.
>
> Knut - AQB2TC
>
>
> Don Wilhelm-4 wrote:
> >
> > I just thought of something that might help those confused
> by the AGC
> > Threshold setting.
> > One other way to look at the required AGC Threshold level
> is to think of
> > it as an S-meter level
> > If your noise is S-1 or lower (on the K3's S-meter), you
> can set the
> > Threshold to 002 or higher and all may be well
> > OTOH, if you have an S-7 noise level indicated, the AGC
> Threshold should
> > be set to 008 or higher.
> > <snip>
> >
>
> --
> View this message in context:
> http://n2.nabble.com/Attenuator-and-RF-Gain-Settings-tp4503505

p4504035.html
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